Oracle® Database SQL Language Reference 11g Release 2 (11.2) Part Number E17118-04 |
|
|
PDF · Mobi · ePub |
Each value manipulated by Oracle Database has a data type. The data type of a value associates a fixed set of properties with the value. These properties cause Oracle to treat values of one data type differently from values of another. For example, you can add values of NUMBER
data type, but not values of RAW
data type.
When you create a table or cluster, you must specify a data type for each of its columns. When you create a procedure or stored function, you must specify a data type for each of its arguments. These data types define the domain of values that each column can contain or each argument can have. For example, DATE
columns cannot accept the value February 29 (except for a leap year) or the values 2 or 'SHOE'. Each value subsequently placed in a column assumes the data type of the column. For example, if you insert '01-JAN-98'
into a DATE
column, then Oracle treats the '01-JAN-98'
character string as a DATE
value after verifying that it translates to a valid date.
Oracle Database provides a number of built-in data types as well as several categories for user-defined types that can be used as data types. The syntax of Oracle data types appears in the diagrams that follow. The text of this section is divided into the following sections:
A data type is either scalar or nonscalar. A scalar type contains an atomic value, whereas a nonscalar (sometimes called a "collection") contains a set of values. A large object (LOB) is a special form of scalar data type representing a large scalar value of binary or character data. LOBs are subject to some restrictions that do not affect other scalar types because of their size. Those restrictions are documented in the context of the relevant SQL syntax.
See Also:
"Restrictions on LOB Columns"The Oracle precompilers recognize other data types in embedded SQL programs. These data types are called external data types and are associated with host variables. Do not confuse built-in data types and user-defined types with external data types. For information on external data types, including how Oracle converts between them and built-in data types or user-defined types, see Pro*COBOL Programmer's Guide, and Pro*C/C++ Programmer's Guide.
The Oracle built-in data types appear in the figures that follows. For descriptions, refer to "Oracle Built-in Data Types".
The ANSI-supported data types appear in the figure that follows. "ANSI, DB2, and SQL/DS Data Types" discusses the mapping of ANSI-supported data types to Oracle built-in data types.
For descriptions of user-defined types, refer to "User-Defined Types".
The Oracle-supplied data types appear in the figures that follows. For descriptions, refer to "Oracle-Supplied Types".
For a description of the expression_filter_type
, refer to "Expression Filter Type". Other Oracle-supplied types follow:
For descriptions of the Any
types, refer to "Any Types".
For descriptions of the XML types, refer to "XML Types".
For descriptions of the spatial types, refer to "Spatial Types".
For descriptions of the media types, refer to "Media Types".
The table that follows summarizes Oracle built-in data types. Refer to the syntax in the preceding sections for the syntactic elements. The codes listed for the data types are used internally by Oracle Database. The data type code of a column or object attribute is returned by the DUMP
function.
Table 3-1 Built-in Data Type Summary
Code | Data Type | Description |
---|---|---|
1 |
|
Variable-length character string having maximum length
|
1 |
|
Variable-length Unicode character string having maximum length |
2 |
|
Number having precision |
2 |
|
A subtype of the |
8 |
|
Character data of variable length up to 2 gigabytes, or 231 -1 bytes. Provided for backward compatibility. |
12 |
|
Valid date range from January 1, 4712 BC, to December 31, 9999 AD. The default format is determined explicitly by the |
21 |
|
32-bit floating point number. This data type requires 4 bytes. |
22 |
|
64-bit floating point number. This data type requires 8 bytes. |
180 |
|
Year, month, and day values of date, as well as hour, minute, and second values of time, where |
181 |
|
All values of |
231 |
|
All values of
The default format is determined explicitly by the |
182 |
|
Stores a period of time in years and months, where |
183 |
|
Stores a period of time in days, hours, minutes, and seconds, where
The size is fixed at 11 bytes. |
23 |
|
Raw binary data of length |
24 |
|
Raw binary data of variable length up to 2 gigabytes. |
69 |
|
Base 64 string representing the unique address of a row in its table. This data type is primarily for values returned by the |
208 |
|
Base 64 string representing the logical address of a row of an index-organized table. The optional |
96 |
|
Fixed-length character data of length
|
96 |
|
Fixed-length character data of length |
112 |
|
A character large object containing single-byte or multibyte characters. Both fixed-width and variable-width character sets are supported, both using the database character set. Maximum size is (4 gigabytes - 1) * (database block size). |
112 |
|
A character large object containing Unicode characters. Both fixed-width and variable-width character sets are supported, both using the database national character set. Maximum size is (4 gigabytes - 1) * (database block size). Stores national character set data. |
113 |
|
A binary large object. Maximum size is (4 gigabytes - 1) * (database block size). |
114 |
|
Contains a locator to a large binary file stored outside the database. Enables byte stream I/O access to external LOBs residing on the database server. Maximum size is 4 gigabytes. |
The sections that follow describe the Oracle data types as they are stored in Oracle Database. For information on specifying these data types as literals, refer to "Literals".
Character data types store character (alphanumeric) data, which are words and free-form text, in the database character set or national character set. They are less restrictive than other data types and consequently have fewer properties. For example, character columns can store all alphanumeric values, but NUMBER
columns can store only numeric values.
Character data is stored in strings with byte values corresponding to one of the character sets, such as 7-bit ASCII or EBCDIC, specified when the database was created. Oracle Database supports both single-byte and multibyte character sets.
These data types are used for character data:
For information on specifying character data types as literals, refer to "Text Literals".
The CHAR
data type specifies a fixed-length character string. Oracle ensures that all values stored in a CHAR
column have the length specified by size
. If you insert a value that is shorter than the column length, then Oracle blank-pads the value to column length. If you try to insert a value that is too long for the column, then Oracle returns an error.
The default length for a CHAR
column is 1 byte and the maximum allowed is 2000 bytes. A 1-byte string can be inserted into a CHAR(10)
column, but the string is blank-padded to 10 bytes before it is stored.
When you create a table with a CHAR
column, by default you supply the column length in bytes. The BYTE
qualifier is the same as the default. If you use the CHAR
qualifier, for example CHAR
(10
CHAR
), then you supply the column length in characters. A character is technically a code point of the database character set. Its size can range from 1 byte to 4 bytes, depending on the database character set. The BYTE
and CHAR
qualifiers override the semantics specified by the NLS_LENGTH_SEMANTICS
parameter, which has a default of byte semantics. For performance reasons, Oracle recommends that you use the NLS_LENGTH_SEMANTICS
parameter to set length semantics and that you use the BYTE
and CHAR
qualifiers only when necessary to override the parameter.
To ensure proper data conversion between databases with different character sets, you must ensure that CHAR
data consists of well-formed strings.
See Also:
Oracle Database Globalization Support Guide for more information on character set support and "Data Type Comparison Rules" for information on comparison semanticsThe NCHAR
data type is a Unicode-only data type. When you create a table with an NCHAR
column, you define the column length in characters. You define the national character set when you create your database.
The maximum length of a column is determined by the national character set definition. Width specifications of character data type NCHAR
refer to the number of characters. The maximum column size allowed is 2000 bytes.
If you insert a value that is shorter than the column length, then Oracle blank-pads the value to column length. You cannot insert a CHAR
value into an NCHAR
column, nor can you insert an NCHAR
value into a CHAR
column.
The following example compares the translated_description
column of the pm.product_descriptions
table with a national character set string:
SELECT translated_description FROM product_descriptions WHERE translated_name = N'LCD Monitor 11/PM';
See Also:
Oracle Database Globalization Support Guide for information on Unicode data type supportThe NVARCHAR2
data type is a Unicode-only data type. When you create a table with an NVARCHAR2
column, you supply the maximum number of characters it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the maximum length of the column.
The maximum length of the column is determined by the national character set definition. Width specifications of character data type NVARCHAR2
refer to the number of characters. The maximum column size allowed is 4000 bytes.
See Also:
Oracle Database Globalization Support Guide for information on Unicode data type support.The VARCHAR2
data type specifies a variable-length character string. When you create a VARCHAR2
column, you supply the maximum number of bytes or characters of data that it can hold. Oracle subsequently stores each value in the column exactly as you specify it, provided the value does not exceed the column's maximum length of the column. If you try to insert a value that exceeds the specified length, then Oracle returns an error.
You must specify a maximum length for a VARCHAR2
column. This maximum must be at least 1 byte, although the actual string stored is permitted to be a zero-length string (''
). You can use the CHAR
qualifier, for example VARCHAR2
(10
CHAR
), to give the maximum length in characters instead of bytes. A character is technically a code point of the database character set. You can use the BYTE
qualifier, for example VARCHAR2
(10 BYTE
), to explicitly give the maximum length in bytes. If no explicit qualifier is included in a column or attribute definition when a database object with this column or attribute is created, then the length semantics are determined by the value of the NLS_LENGTH_SEMANTICS
parameter of the session creating the object. Independently of the maximum length in characters, the length of VARCHAR2
data cannot exceed 4000 bytes. Oracle compares VARCHAR2
values using nonpadded comparison semantics.
To ensure proper data conversion between databases with different character sets, you must ensure that VARCHAR2
data consists of well-formed strings. See Oracle Database Globalization Support Guide for more information on character set support.
See Also:
"Data Type Comparison Rules" for information on comparison semanticsDo not use the VARCHAR
data type. Use the VARCHAR2
data type instead. Although the VARCHAR
data type is currently synonymous with VARCHAR2
, the VARCHAR
data type is scheduled to be redefined as a separate data type used for variable-length character strings compared with different comparison semantics.
The Oracle Database numeric data types store positive and negative fixed and floating-point numbers, zero, infinity, and values that are the undefined result of an operation—"not a number" or NAN
. For information on specifying numeric data types as literals, refer to "Numeric Literals".
The NUMBER
data type stores zero as well as positive and negative fixed numbers with absolute values from 1.0 x 10-130 to but not including 1.0 x 10126. If you specify an arithmetic expression whose value has an absolute value greater than or equal to 1.0 x 10126, then Oracle returns an error. Each NUMBER
value requires from 1 to 22 bytes.
Specify a fixed-point number using the following form:
NUMBER(p,s)
where:
p
is the precision, or the maximum number of significant decimal digits, where the most significant digit is the left-most nonzero digit, and the least significant digit is the right-most known digit. Oracle guarantees the portability of numbers with precision of up to 20 base-100 digits, which is equivalent to 39 or 40 decimal digits depending on the position of the decimal point.
s
is the scale, or the number of digits from the decimal point to the least significant digit. The scale can range from -84 to 127.
Positive scale is the number of significant digits to the right of the decimal point to and including the least significant digit.
Negative scale is the number of significant digits to the left of the decimal point, to but not including the least significant digit. For negative scale the least significant digit is on the left side of the decimal point, because the actual data is rounded to the specified number of places to the left of the decimal point. For example, a specification of (10,-2) means to round to hundreds.
Scale can be greater than precision, most commonly when e
notation is used. When scale is greater than precision, the precision specifies the maximum number of significant digits to the right of the decimal point. For example, a column defined as NUMBER(4,5)
requires a zero for the first digit after the decimal point and rounds all values past the fifth digit after the decimal point.
It is good practice to specify the scale and precision of a fixed-point number column for extra integrity checking on input. Specifying scale and precision does not force all values to a fixed length. If a value exceeds the precision, then Oracle returns an error. If a value exceeds the scale, then Oracle rounds it.
Specify an integer using the following form:
NUMBER(p)
This represents a fixed-point number with precision p
and scale 0 and is equivalent to NUMBER(p,0)
.
Specify a floating-point number using the following form:
NUMBER
The absence of precision and scale designators specifies the maximum range and precision for an Oracle number.
See Also:
"Floating-Point Numbers"Table 3-2 show how Oracle stores data using different precisions and scales.
Table 3-2 Storage of Scale and Precision
Actual Data | Specified As | Stored As |
---|---|---|
123.89 |
|
123.89 |
123.89 |
|
124 |
123.89 |
|
exceeds precision |
123.89 |
|
exceeds precision |
123.89 |
|
123.89 |
123.89 |
|
123.9 |
123.89 |
|
100 |
.01234 |
|
.01234 |
.00012 |
|
.00012 |
.000127 |
|
.00013 |
.0000012 |
|
.0000012 |
.00000123 |
|
.0000012 |
1.2e-4 |
|
0.00012 |
1.2e-5 |
|
0.00001 |
The FLOAT
data type is a subtype of NUMBER
. It can be specified with or without precision, which has the same definition it has for NUMBER
and can range from 1 to 126. Scale cannot be specified, but is interpreted from the data. Each FLOAT
value requires from 1 to 22 bytes.
To convert from binary to decimal precision, multiply n
by 0.30103. To convert from decimal to binary precision, multiply the decimal precision by 3.32193. The maximum of 126 digits of binary precision is roughly equivalent to 38 digits of decimal precision.
The difference between NUMBER
and FLOAT
is best illustrated by example. In the following example the same values are inserted into NUMBER
and FLOAT
columns:
CREATE TABLE test (col1 NUMBER(5,2), col2 FLOAT(5)); INSERT INTO test VALUES (1.23, 1.23); INSERT INTO test VALUES (7.89, 7.89); INSERT INTO test VALUES (12.79, 12.79); INSERT INTO test VALUES (123.45, 123.45); SELECT * FROM test; COL1 COL2 ---------- ---------- 1.23 1.2 7.89 7.9 12.79 13 123.45 120
In this example, the FLOAT
value returned cannot exceed 5 binary digits. The largest decimal number that can be represented by 5 binary digits is 31. The last row contains decimal values that exceed 31. Therefore, the FLOAT
value must be truncated so that its significant digits do not require more than 5 binary digits. Thus 123.45 is rounded to 120, which has only two significant decimal digits, requiring only 4 binary digits.
Oracle Database uses the Oracle FLOAT
data type internally when converting ANSI FLOAT
data. Oracle FLOAT
is available for you to use, but Oracle recommends that you use the BINARY_FLOAT
and BINARY_DOUBLE
data types instead, as they are more robust. Refer to "Floating-Point Numbers" for more information.
Floating-point numbers can have a decimal point anywhere from the first to the last digit or can have no decimal point at all. An exponent may optionally be used following the number to increase the range, for example, 1.777 e-20. A scale value is not applicable to floating-point numbers, because the number of digits that can appear after the decimal point is not restricted.
Binary floating-point numbers differ from NUMBER
in the way the values are stored internally by Oracle Database. Values are stored using decimal precision for NUMBER
. All literals that are within the range and precision supported by NUMBER
are stored exactly as NUMBER
. Literals are stored exactly because literals are expressed using decimal precision (the digits 0 through 9). Binary floating-point numbers are stored using binary precision (the digits 0 and 1). Such a storage scheme cannot represent all values using decimal precision exactly. Frequently, the error that occurs when converting a value from decimal to binary precision is undone when the value is converted back from binary to decimal precision. The literal 0.1 is such an example.
Oracle Database provides two numeric data types exclusively for floating-point numbers:
BINARY_FLOAT
is a 32-bit, single-precision floating-point number data type. Each BINARY_FLOAT
value requires 4 bytes.
BINARY_DOUBLE
is a 64-bit, double-precision floating-point number data type. Each BINARY_DOUBLE
value requires 8 bytes.
In a NUMBER
column, floating point numbers have decimal precision. In a BINARY_FLOAT
or BINARY_DOUBLE
column, floating-point numbers have binary precision. The binary floating-point numbers support the special values infinity and NaN
(not a number).
You can specify floating-point numbers within the limits listed in Table 3-3. The format for specifying floating-point numbers is defined in "Numeric Literals".
Table 3-3 Floating Point Number Limits
Value | BINARY_FLOAT | BINARY_DOUBLE |
---|---|---|
Maximum positive finite value |
3.40282E+38F |
1.79769313486231E+308 |
Minimum positive finite value |
1.17549E-38F |
2.22507485850720E-308 |
IEEE754 Conformance The Oracle implementation of floating-point data types conforms substantially with the Institute of Electrical and Electronics Engineers (IEEE) Standard for Binary Floating-Point Arithmetic, IEEE Standard 754-1985 (IEEE754). The floating-point data types conform to IEEE754 in the following areas:
The SQL function SQRT
implements square root. See SQRT.
The SQL function REMAINDER
implements remainder. See REMAINDER.
Arithmetic operators conform. See "Arithmetic Operators".
Comparison operators conform, except for comparisons with NaN
. Oracle orders NaN
greatest with respect to all other values, and evaluates NaN
equal to NaN
. See "Floating-Point Conditions".
Conversion operators conform. See "Conversion Functions".
The default rounding mode is supported.
The default exception handling mode is supported.
The special values INF
, -INF
, and NaN
are supported. See "Floating-Point Conditions".
Rounding of BINARY_FLOAT
and BINARY_DOUBLE
values to integer-valued BINARY_FLOAT
and BINARY_DOUBLE
values is provided by the SQL functions ROUND
, TRUNC
, CEIL
, and FLOOR
.
Rounding of BINARY_FLOAT
/BINARY_DOUBLE
to decimal and decimal to BINARY_FLOAT
/BINARY_DOUBLE
is provided by the SQL functions TO_CHAR
, TO_NUMBER
, TO_NCHAR
, TO_BINARY_FLOAT
, TO_BINARY_DOUBLE
, and CAST
.
The floating-point data types do not conform to IEEE754 in the following areas:
-0 is coerced to +0.
Comparison with NaN
is not supported.
All NaN
values are coerced to either BINARY_FLOAT_NAN
or BINARY_DOUBLE_NAN
.
Non-default rounding modes are not supported.
Non-default exception handling mode are not supported.
Numeric precedence determines, for operations that support numeric data types, the data type Oracle uses if the arguments to the operation have different data types. BINARY_DOUBLE
has the highest numeric precedence, followed by BINARY_FLOAT
, and finally by NUMBER
. Therefore, in any operation on multiple numeric values:
If any of the operands is BINARY_DOUBLE
, then Oracle attempts to convert all the operands implicitly to BINARY_DOUBLE
before performing the operation.
If none of the operands is BINARY_DOUBLE
but any of the operands is BINARY_FLOAT
, then Oracle attempts to convert all the operands implicitly to BINARY_FLOAT
before performing the operation.
Otherwise, Oracle attempts to convert all the operands to NUMBER
before performing the operation.
If any implicit conversion is needed and fails, then the operation fails. Refer to Table 3-10, "Implicit Type Conversion Matrix" for more information on implicit conversion.
In the context of other data types, numeric data types have lower precedence than the datetime/interval data types and higher precedence than character and all other data types.
Do not create tables with LONG
columns. Use LOB columns (CLOB
, NCLOB
, BLOB
) instead. LONG
columns are supported only for backward compatibility.
LONG
columns store variable-length character strings containing up to 2 gigabytes -1, or 231-1 bytes. LONG
columns have many of the characteristics of VARCHAR2
columns. You can use LONG
columns to store long text strings. The length of LONG
values may be limited by the memory available on your computer. LONG
literals are formed as described for "Text Literals".
Oracle also recommends that you convert existing LONG
columns to LOB columns. LOB columns are subject to far fewer restrictions than LONG
columns. Further, LOB functionality is enhanced in every release, whereas LONG
functionality has been static for several releases. See the modify_col_properties
clause of ALTER TABLE and TO_LOB for more information on converting LONG
columns to LOB.
You can reference LONG
columns in SQL statements in these places:
SELECT
lists
SET
clauses of UPDATE
statements
VALUES
clauses of INSERT
statements
The use of LONG
values is subject to these restrictions:
A table can contain only one LONG
column.
You cannot create an object type with a LONG
attribute.
LONG
columns cannot appear in WHERE
clauses or in integrity constraints (except that they can appear in NULL
and NOT
NULL
constraints).
LONG
columns cannot be indexed.
LONG
data cannot be specified in regular expressions.
A stored function cannot return a LONG
value.
You can declare a variable or argument of a PL/SQL program unit using the LONG
data type. However, you cannot then call the program unit from SQL.
Within a single SQL statement, all LONG
columns, updated tables, and locked tables must be located on the same database.
LONG
and LONG
RAW
columns cannot be used in distributed SQL statements and cannot be replicated.
If a table has both LONG
and LOB columns, then you cannot bind more than 4000 bytes of data to both the LONG
and LOB columns in the same SQL statement. However, you can bind more than 4000 bytes of data to either the LONG
or the LOB column.
In addition, LONG
columns cannot appear in these parts of SQL statements:
GROUP
BY
clauses, ORDER
BY
clauses, or CONNECT
BY
clauses or with the DISTINCT
operator in SELECT
statements
The UNIQUE
operator of a SELECT
statement
The column list of a CREATE
CLUSTER
statement
The CLUSTER
clause of a CREATE
MATERIALIZED
VIEW
statement
SQL built-in functions, expressions, or conditions
SELECT
lists of queries containing GROUP
BY
clauses
SELECT
lists of subqueries or queries combined by the UNION
, INTERSECT
, or MINUS
set operators
SELECT
lists of CREATE
TABLE
... AS
SELECT
statements
ALTER
TABLE
... MOVE
statements
SELECT
lists in subqueries in INSERT
statements
Triggers can use the LONG
data type in the following manner:
A SQL statement within a trigger can insert data into a LONG
column.
If data from a LONG
column can be converted to a constrained data type (such as CHAR
and VARCHAR2
), then a LONG
column can be referenced in a SQL statement within a trigger.
Variables in triggers cannot be declared using the LONG
data type.
:NEW
and :OLD
cannot be used with LONG
columns.
You can use Oracle Call Interface functions to retrieve a portion of a LONG
value from the database.
See Also:
Oracle Call Interface Programmer's GuideDatetime and Interval Data Types
The datetime data types are DATE
, TIMESTAMP
, TIMESTAMP
WITH
TIME
ZONE
, and TIMESTAMP
WITH
LOCAL
TIME
ZONE
. Values of datetime data types are sometimes called datetimes. The interval data types are INTERVAL
YEAR
TO
MONTH
and INTERVAL
DAY
TO
SECOND
. Values of interval data types are sometimes called intervals. For information on expressing datetime and interval values as literals, refer to "Datetime Literals" and "Interval Literals".
Both datetimes and intervals are made up of fields. The values of these fields determine the value of the data type. Table 3-4 lists the datetime fields and their possible values for datetimes and intervals.
To avoid unexpected results in your DML operations on datetime data, you can verify the database and session time zones by querying the built-in SQL functions DBTIMEZONE
and SESSIONTIMEZONE
. If the time zones have not been set manually, then Oracle Database uses the operating system time zone by default. If the operating system time zone is not a valid Oracle time zone, then Oracle uses UTC as the default value.
Table 3-4 Datetime Fields and Values
Datetime Field | Valid Values for Datetime | Valid Values for INTERVAL |
---|---|---|
|
-4712 to 9999 (excluding year 0) |
Any positive or negative integer |
|
01 to 12 |
0 to 11 |
|
01 to 31 (limited by the values of |
Any positive or negative integer |
|
00 to 23 |
0 to 23 |
|
00 to 59 |
0 to 59 |
|
00 to 59.9(n), where 9(n) is the precision of time fractional seconds. The 9(n) portion is not applicable for |
0 to 59.9(n), where 9(n) is the precision of interval fractional seconds |
|
-12 to 14 (This range accommodates daylight saving time changes.) Not applicable for |
Not applicable |
(See note at end of table) |
00 to 59. Not applicable for |
Not applicable |
|
Query the |
Not applicable |
|
Query the |
Not applicable |
Note:
TIMEZONE_HOUR
and TIMEZONE_MINUTE
are specified together and interpreted as an entity in the format +|- hh:mm, with values ranging from -12:59 to +14:00. Refer to Oracle Data Provider for .NET Developer's Guide for information on specifying time zone values for that API.The DATE
data type stores date and time information. Although date and time information can be represented in both character and number data types, the DATE
data type has special associated properties. For each DATE
value, Oracle stores the following information: century, year, month, date, hour, minute, and second.
You can specify a DATE
value as a literal, or you can convert a character or numeric value to a date value with the TO_DATE
function. For examples of expressing DATE
values in both these ways, refer to "Datetime Literals".
A Julian day number is the number of days since January 1, 4712 BC. Julian days allow continuous dating from a common reference. You can use the date format model "J" with date functions TO_DATE
and TO_CHAR
to convert between Oracle DATE
values and their Julian equivalents.
Note:
Oracle Database uses the astronomical system of calculating Julian days, in which the year 4713 BC is specified as -4712. The historical system of calculating Julian days, in contrast, specifies 4713 BC as -4713. If you are comparing Oracle Julian days with values calculated using the historical system, then take care to allow for the 365-day difference in BC dates. For more information, seehttp://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/millennium
.The default date values are determined as follows:
The year is the current year, as returned by SYSDATE
.
The month is the current month, as returned by SYSDATE
.
The day is 01 (the first day of the month).
The hour, minute, and second are all 0.
These default values are used in a query that requests date values where the date itself is not specified, as in the following example, which is issued in the month of May:
SELECT TO_DATE('2009', 'YYYY') FROM DUAL; TO_DATE(' --------- 01-MAY-09
Example This statement returns the Julian equivalent of January 1, 1997:
SELECT TO_CHAR(TO_DATE('01-01-2009', 'MM-DD-YYYY'),'J') FROM DUAL; TO_CHAR ------- 2454833
The TIMESTAMP
data type is an extension of the DATE
data type. It stores the year, month, and day of the DATE
data type, plus hour, minute, and second values. This data type is useful for storing precise time values and for collecting and evaluating date information across geographic regions. Specify the TIMESTAMP
data type as follows:
TIMESTAMP [(fractional_seconds_precision)]
where fractional_seconds_precision
optionally specifies the number of digits Oracle stores in the fractional part of the SECOND
datetime field. When you create a column of this data type, the value can be a number in the range 0 to 9. The default is 6.
TIMESTAMP
WITH
TIME
ZONE
is a variant of TIMESTAMP
that includes a time zone region name or a time zone offset in its value. The time zone offset is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). This data type is useful for preserving local time zone information.
Specify the TIMESTAMP
WITH
TIME
ZONE
data type as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE
where fractional_seconds_precision
optionally specifies the number of digits Oracle stores in the fractional part of the SECOND
datetime field. When you create a column of this data type, the value can be a number in the range 0 to 9. The default is 6.
Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/
. Oracle time zone data may not reflect the most recent data available at this site.
See Also:
Oracle Database Globalization Support Guide for more information on Oracle time zone data
"Support for Daylight Saving Times" and Table 3-17, "Matching Character Data and Format Models with the FX Format Model Modifier" for information on daylight saving support
TO_TIMESTAMP_TZ for information on converting character data to TIMESTAMP
WITH
TIME
ZONE
data
ALTER SESSION for information on the ERROR_ON_OVERLAP_TIME
session parameter
TIMESTAMP
WITH
LOCAL
TIME
ZONE
is another variant of TIMESTAMP
that includes a time zone offset in its value. It differs from TIMESTAMP
WITH
TIME
ZONE
in that data stored in the database is normalized to the database time zone, and the time zone offset is not stored as part of the column data. When a user retrieves the data, Oracle returns it in the user's local session time zone. The time zone offset is the difference (in hours and minutes) between local time and UTC (Coordinated Universal Time—formerly Greenwich Mean Time). This data type is useful for displaying date information in the time zone of the client system in a two-tier application.
Specify the TIMESTAMP
WITH
LOCAL
TIME
ZONE
data type as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE
where fractional_seconds_precision
optionally specifies the number of digits Oracle stores in the fractional part of the SECOND
datetime field. When you create a column of this data type, the value can be a number in the range 0 to 9. The default is 6.
Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/
. Oracle time zone data may not reflect the most recent data available at this site.
See Also:
Oracle Database Globalization Support Guide for more information on Oracle time zone data
Oracle Database Advanced Application Developer's Guide for examples of using this data type and CAST for information on converting character data to TIMESTAMP
WITH
LOCAL
TIME
ZONE
INTERVAL
YEAR
TO
MONTH
stores a period of time using the YEAR
and MONTH
datetime fields. This data type is useful for representing the difference between two datetime values when only the year and month values are significant.
Specify INTERVAL
YEAR
TO
MONTH
as follows:
INTERVAL YEAR [(year_precision)] TO MONTH
where year_precision
is the number of digits in the YEAR
datetime field. The default value of year_precision
is 2.
You have a great deal of flexibility when specifying interval values as literals. Refer to "Interval Literals" for detailed information on specifying interval values as literals. Also see "Datetime and Interval Examples" for an example using intervals.
INTERVAL
DAY
TO
SECOND
stores a period of time in terms of days, hours, minutes, and seconds. This data type is useful for representing the precise difference between two datetime values.
Specify this data type as follows:
INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)]
where
day_precision
is the number of digits in the DAY
datetime field. Accepted values are 0 to 9. The default is 2.
fractional_seconds_precision
is the number of digits in the fractional part of the SECOND
datetime field. Accepted values are 0 to 9. The default is 6.
You have a great deal of flexibility when specifying interval values as literals. Refer to "Interval Literals" for detailed information on specify interval values as literals. Also see "Datetime and Interval Examples" for an example using intervals.
You can perform a number of arithmetic operations on date (DATE
), timestamp (TIMESTAMP
, TIMESTAMP
WITH
TIME
ZONE
, and TIMESTAMP
WITH
LOCAL
TIME
ZONE
) and interval (INTERVAL
DAY
TO
SECOND
and INTERVAL
YEAR
TO
MONTH
) data. Oracle calculates the results based on the following rules:
You can use NUMBER
constants in arithmetic operations on date and timestamp values, but not interval values. Oracle internally converts timestamp values to date values and interprets NUMBER
constants in arithmetic datetime and interval expressions as numbers of days. For example, SYSDATE
+ 1 is tomorrow. SYSDATE
- 7 is one week ago. SYSDATE
+ (10/1440) is ten minutes from now. Subtracting the hire_date
column of the sample table employees
from SYSDATE
returns the number of days since each employee was hired. You cannot multiply or divide date or timestamp values.
Oracle implicitly converts BINARY_FLOAT
and BINARY_DOUBLE
operands to NUMBER
.
Each DATE
value contains a time component, and the result of many date operations include a fraction. This fraction means a portion of one day. For example, 1.5 days is 36 hours. These fractions are also returned by Oracle built-in functions for common operations on DATE
data. For example, the MONTHS_BETWEEN
function returns the number of months between two dates. The fractional portion of the result represents that portion of a 31-day month.
If one operand is a DATE
value or a numeric value, neither of which contains time zone or fractional seconds components, then:
Oracle implicitly converts the other operand to DATE
data. The exception is multiplication of a numeric value times an interval, which returns an interval.
If the other operand has a time zone value, then Oracle uses the session time zone in the returned value.
If the other operand has a fractional seconds value, then the fractional seconds value is lost.
When you pass a timestamp, interval, or numeric value to a built-in function that was designed only for the DATE
data type, Oracle implicitly converts the non-DATE
value to a DATE
value. Refer to "Datetime Functions" for information on which functions cause implicit conversion to DATE
.
When interval calculations return a datetime value, the result must be an actual datetime value or the database returns an error. For example, the next two statements return errors:
SELECT TO_DATE('31-AUG-2004','DD-MON-YYYY') + TO_YMINTERVAL('0-1') FROM DUAL; SELECT TO_DATE('29-FEB-2004','DD-MON-YYYY') + TO_YMINTERVAL('1-0') FROM DUAL;
The first fails because adding one month to a 31-day month would result in September 31, which is not a valid date. The second fails because adding one year to a date that exists only every four years is not valid. However, the next statement succeeds, because adding four years to a February 29 date is valid:
SELECT TO_DATE('29-FEB-2004', 'DD-MON-YYYY') + TO_YMINTERVAL('4-0') FROM DUAL; TO_DATE(' --------- 29-FEB-08
Oracle performs all timestamp arithmetic in UTC time. For TIMESTAMP
WITH
LOCAL
TIME
ZONE
, Oracle converts the datetime value from the database time zone to UTC and converts back to the database time zone after performing the arithmetic. For TIMESTAMP
WITH
TIME
ZONE
, the datetime value is always in UTC, so no conversion is necessary.
Table 3-5 is a matrix of datetime arithmetic operations. Dashes represent operations that are not supported.
Table 3-5 Matrix of Datetime Arithmetic
Operand & Operator | DATE | TIMESTAMP | INTERVAL | Numeric |
---|---|---|---|---|
DATE |
||||
+ |
|
|
|
|
- |
|
|
|
|
* |
|
|
|
|
/ |
|
|
|
|
TIMESTAMP |
||||
+ |
|
|
|
|
- |
|
|
|
|
* |
|
|
|
|
/ |
|
|
|
|
INTERVAL |
||||
+ |
|
|
|
|
- |
|
|
|
|
* |
|
|
|
|
/ |
|
|
|
|
Numeric |
||||
+ |
|
|
|
|
- |
|
|
|
|
* |
|
|
|
|
/ |
|
|
|
|
Examples You can add an interval value expression to a start time. Consider the sample table oe.orders
with a column order_date
. The following statement adds 30 days to the value of the order_date
column:
SELECT order_id, order_date + INTERVAL '30' DAY AS "Due Date" FROM orders ORDER BY order_id, "Due Date";
Oracle Database automatically determines, for any given time zone region, whether daylight saving is in effect and returns local time values accordingly. The datetime value is sufficient for Oracle to determine whether daylight saving time is in effect for a given region in all cases except boundary cases. A boundary case occurs during the period when daylight saving goes into or comes out of effect. For example, in the US-Pacific region, when daylight saving goes into effect, the time changes from 2:00 a.m. to 3:00 a.m. The one hour interval between 2 and 3 a.m. does not exist. When daylight saving goes out of effect, the time changes from 2:00 a.m. back to 1:00 a.m., and the one-hour interval between 1 and 2 a.m. is repeated.
To resolve these boundary cases, Oracle uses the TZR
and TZD
format elements, as described in Table 3-17. TZR
represents the time zone region name in datetime input strings. Examples are 'Australia/North
', 'UTC
', and 'Singapore
'. TZD
represents an abbreviated form of the time zone region name with daylight saving information. Examples are 'PST
' for US/Pacific standard time and 'PDT
' for US/Pacific daylight time. To see a listing of valid values for the TZR
and TZD
format elements, query the TZNAME
and TZABBREV
columns of the V$TIMEZONE_NAMES
dynamic performance view.
Note:
Time zone region names are needed by the daylight saving feature. These names are stored in two types of time zone files: one large and one small. One of these files is the default file, depending on your environment and the release of Oracle Database you are using. For more information regarding time zone files and names, see Oracle Database Globalization Support Guide.For a complete listing of the time zone region names in both files, refer to Oracle Database Globalization Support Guide.
Oracle time zone data is derived from the public domain information available at ftp://elsie.nci.nih.gov/pub/
. Oracle time zone data may not reflect the most recent data available at this site.
See Also:
"Datetime Format Models" for information on the format elements and the session parameter ERROR_ON_OVERLAP_TIME.
Oracle Database Globalization Support Guide for more information on Oracle time zone data
Oracle Database Reference for information on the dynamic performance views
The following example shows how to specify some datetime and interval data types.
CREATE TABLE time_table (start_time TIMESTAMP, duration_1 INTERVAL DAY (6) TO SECOND (5), duration_2 INTERVAL YEAR TO MONTH);
The start_time
column is of type TIMESTAMP
. The implicit fractional seconds precision of TIMESTAMP
is 6.
The duration_1
column is of type INTERVAL
DAY
TO
SECOND
. The maximum number of digits in field DAY
is 6 and the maximum number of digits in the fractional second is 5. The maximum number of digits in all other datetime fields is 2.
The duration_2
column is of type INTERVAL
YEAR
TO
MONTH
. The maximum number of digits of the value in each field (YEAR
and MONTH
) is 2.
Interval data types do not have format models. Therefore, to adjust their presentation, you must combine character functions such as EXTRACT
and concatenate the components. For example, the following examples query the hr.employees
and oe.orders
tables, respectively, and change interval output from the form "yy-mm" to "yy years mm months" and from "dd-hh" to "dddd days hh hours":
SELECT last_name, EXTRACT(YEAR FROM (SYSDATE - hire_date) YEAR TO MONTH) || ' years ' || EXTRACT(MONTH FROM (SYSDATE - hire_date) YEAR TO MONTH) || ' months' "Interval" FROM employees; LAST_NAME Interval ------------------------- -------------------- OConnell 2 years 3 months Grant 1 years 9 months Whalen 6 years 1 months Hartstein 5 years 8 months Fay 4 years 2 months Mavris 7 years 4 months Baer 7 years 4 months Higgins 7 years 4 months Gietz 7 years 4 months . . . SELECT order_id, EXTRACT(DAY FROM (SYSDATE - order_date) DAY TO SECOND) || ' days ' || EXTRACT(HOUR FROM (SYSDATE - order_date) DAY TO SECOND) || ' hours' "Interval" FROM orders; ORDER_ID Interval ---------- -------------------- 2458 780 days 23 hours 2397 685 days 22 hours 2454 733 days 21 hours 2354 447 days 20 hours 2358 635 days 20 hours 2381 508 days 18 hours 2440 765 days 17 hours 2357 1365 days 16 hours 2394 602 days 15 hours 2435 763 days 15 hours . . .
The RAW
and LONG
RAW
data types store data that is not to be explicitly converted by Oracle Database when moving data between different systems. These data types are intended for binary data or byte strings. For example, you can use LONG
RAW
to store graphics, sound, documents, or arrays of binary data, for which the interpretation is dependent on the use.
Oracle strongly recommends that you convert LONG
RAW
columns to binary LOB (BLOB
) columns. LOB columns are subject to far fewer restrictions than LONG
columns. See TO_LOB for more information.
RAW
is a variable-length data type like VARCHAR2
, except that Oracle Net (which connects user sessions to the instance) and the Oracle import and export utilities do not perform character conversion when transmitting RAW
or LONG
RAW
data. In contrast, Oracle Net and the Oracle import and export utilities automatically convert CHAR
, VARCHAR2
, and LONG
data from the database character set to the user session character set. If the two character sets are different, you can set the user session character set with the NLS_LANGUAGE
parameter of the ALTER
SESSION
statement.
When Oracle automatically converts RAW
or LONG
RAW
data to and from CHAR
data, the binary data is represented in hexadecimal form, with one hexadecimal character representing every four bits of RAW
data. For example, one byte of RAW
data with bits 11001011 is displayed and entered as CB
.
The built-in LOB data types BLOB
, CLOB
, and NCLOB
(stored internally) and BFILE
(stored externally) can store large and unstructured data such as text, image, video, and spatial data. The size of BLOB
, CLOB
, and NCLOB
data can be up to (232-1 bytes) * (the value of the CHUNK
parameter of LOB storage). If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK
parameter of LOB storage when creating a LOB column, then this is equivalent to (232-1 bytes) * (database block size). BFILE
data can be up to 264-1 bytes, although your operating system may impose restrictions on this maximum.
When creating a table, you can optionally specify different tablespace and storage characteristics for LOB columns or LOB object attributes from those specified for the table.
CLOB
, NCLOB
, and BLOB
values up to approximately 4000 bytes are stored inline if you enable storage in row at the time the LOB column is created. LOBs greater than 4000 bytes are always stored externally. Refer to ENABLE STORAGE IN ROW for more information.
LOB columns contain LOB locators that can refer to internal (in the database) or external (outside the database) LOB values. Selecting a LOB from a table actually returns the LOB locator and not the entire LOB value. The DBMS_LOB
package and Oracle Call Interface (OCI) operations on LOBs are performed through these locators.
LOBs are similar to LONG
and LONG
RAW
types, but differ in the following ways:
LOBs can be attributes of an object type (user-defined data type).
The LOB locator is stored in the table column, either with or without the actual LOB value. BLOB
, NCLOB
, and CLOB
values can be stored in separate tablespaces. BFILE
data is stored in an external file on the server.
When you access a LOB column, the locator is returned.
A LOB can be up to (232-1 bytes)*(database block size) in size. BFILE
data can be up to 264-1 bytes, although your operating system may impose restrictions on this maximum.
LOBs permit efficient, random, piece-wise access to and manipulation of data.
You can define more than one LOB column in a table.
With the exception of NCLOB
, you can define one or more LOB attributes in an object.
You can declare LOB bind variables.
You can select LOB columns and LOB attributes.
You can insert a new row or update an existing row that contains one or more LOB columns or an object with one or more LOB attributes. In update operations, you can set the internal LOB value to NULL
, empty, or replace the entire LOB with data. You can set the BFILE
to NULL
or make it point to a different file.
You can update a LOB row-column intersection or a LOB attribute with another LOB row-column intersection or LOB attribute.
You can delete a row containing a LOB column or LOB attribute and thereby also delete the LOB value. For BFILEs, the actual operating system file is not deleted.
You can access and populate rows of an inline LOB column (a LOB column stored in the database) or a LOB attribute (an attribute of an object type column stored in the database) simply by issuing an INSERT
or UPDATE
statement.
Restrictions on LOB Columns LOB columns are subject to a number of rules and restrictions. See Oracle Database SecureFiles and Large Objects Developer's Guide for a complete listing.
See Also:
Oracle Database PL/SQL Packages and Types Reference and Oracle Call Interface Programmer's Guide for more information about these interfaces and LOBs
the modify_col_properties
clause of ALTER TABLE and TO_LOB for more information on converting LONG
columns to LOB columns
The BFILE
data type enables access to binary file LOBs that are stored in file systems outside Oracle Database. A BFILE
column or attribute stores a BFILE
locator, which serves as a pointer to a binary file on the server file system. The locator maintains the directory name and the filename.
You can change the filename and path of a BFILE
without affecting the base table by using the BFILENAME
function. Refer to BFILENAME for more information on this built-in SQL function.
Binary file LOBs do not participate in transactions and are not recoverable. Rather, the underlying operating system provides file integrity and durability. BFILE
data can be up to 264-1 bytes, although your operating system may impose restrictions on this maximum.
The database administrator must ensure that the external file exists and that Oracle processes have operating system read permissions on the file.
The BFILE
data type enables read-only support of large binary files. You cannot modify or replicate such a file. Oracle provides APIs to access file data. The primary interfaces that you use to access file data are the DBMS_LOB
package and Oracle Call Interface (OCI).
See Also:
Oracle Database SecureFiles and Large Objects Developer's Guide and Oracle Call Interface Programmer's Guide for more information about LOBs and CREATE DIRECTORYThe BLOB
data type stores unstructured binary large objects. BLOB
objects can be thought of as bitstreams with no character set semantics. BLOB
objects can store binary data up to (4 gigabytes -1) * (the value of the CHUNK
parameter of LOB storage). If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK
parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size).
BLOB
objects have full transactional support. Changes made through SQL, the DBMS_LOB
package, or Oracle Call Interface (OCI) participate fully in the transaction. BLOB
value manipulations can be committed and rolled back. However, you cannot save a BLOB
locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
The CLOB
data type stores single-byte and multibyte character data. Both fixed-width and variable-width character sets are supported, and both use the database character set. CLOB
objects can store up to (4 gigabytes -1) * (the value of the CHUNK
parameter of LOB storage) of character data. If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK
parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size).
CLOB
objects have full transactional support. Changes made through SQL, the DBMS_LOB
package, or Oracle Call Interface (OCI) participate fully in the transaction. CLOB
value manipulations can be committed and rolled back. However, you cannot save a CLOB
locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
The NCLOB
data type stores Unicode data. Both fixed-width and variable-width character sets are supported, and both use the national character set. NCLOB
objects can store up to (4 gigabytes -1) * (the value of the CHUNK
parameter of LOB storage) of character text data. If the tablespaces in your database are of standard block size, and if you have used the default value of the CHUNK
parameter of LOB storage when creating a LOB column, then this is equivalent to (4 gigabytes - 1) * (database block size).
NCLOB
objects have full transactional support. Changes made through SQL, the DBMS_LOB
package, or OCI participate fully in the transaction. NCLOB
value manipulations can be committed and rolled back. However, you cannot save an NCLOB
locator in a PL/SQL or OCI variable in one transaction and then use it in another transaction or session.
See Also:
Oracle Database Globalization Support Guide for information on Unicode data type supportEach row in the database has an address. The sections that follow describe the two forms of row address in an Oracle Database.
The rows in heap-organized tables that are native to Oracle Database have row addresses called rowids. You can examine a rowid row address by querying the pseudocolumn ROWID
. Values of this pseudocolumn are strings representing the address of each row. These strings have the data type ROWID
. You can also create tables and clusters that contain actual columns having the ROWID
data type. Oracle Database does not guarantee that the values of such columns are valid rowids. Refer to Chapter 2, "Pseudocolumns" for more information on the ROWID
pseudocolumn.
Note:
Beginning with Oracle8, Oracle SQL incorporated an extended format for rowids to efficiently support partitioned tables and indexes and tablespace-relative data block addresses without ambiguity. If you are running Version 7 of the database and you intend to upgrade, use theDBMS_ROWID
package to migrate rowids in your data to the extended format. Refer to Oracle Database PL/SQL Packages and Types Reference for information on DBMS_ROWID
and to Oracle Database Upgrade Guide for information on upgrading from Oracle7.Rowids contain the following information:
The data block of the data file containing the row. The length of this string depends on your operating system.
The row in the data block.
The database file containing the row. The first data file has the number 1. The length of this string depends on your operating system.
The data object number, which is an identification number assigned to every database segment. You can retrieve the data object number from the data dictionary views USER_OBJECTS
, DBA_OBJECTS
, and ALL_OBJECTS
. Objects that share the same segment (clustered tables in the same cluster, for example) have the same object number.
Rowids are stored as base 64 values that can contain the characters A-Z, a-z, 0-9, and the plus sign (+) and forward slash (/). Rowids are not available directly. You can use the supplied package DBMS_ROWID
to interpret rowid contents. The package functions extract and provide information on the four rowid elements listed above.
See Also:
Oracle Database PL/SQL Packages and Types Reference for information on the functions available with theDBMS_ROWID
package and how to use themThe rows of some tables have addresses that are not physical or permanent or were not generated by Oracle Database. For example, the row addresses of index-organized tables are stored in index leaves, which can move. Rowids of foreign tables (such as DB2 tables accessed through a gateway) are not standard Oracle rowids.
Oracle uses universal rowids (urowids) to store the addresses of index-organized and foreign tables. Index-organized tables have logical urowids and foreign tables have foreign urowids. Both types of urowid are stored in the ROWID
pseudocolumn (as are the physical rowids of heap-organized tables).
Oracle creates logical rowids based on the primary key of the table. The logical rowids do not change as long as the primary key does not change. The ROWID
pseudocolumn of an index-organized table has a data type of UROWID
. You can access this pseudocolumn as you would the ROWID
pseudocolumn of a heap-organized table (using a SELECT
... ROWID
statement). If you want to
store the rowids of an index-organized table, then you can define a column of type UROWID
for the table and retrieve the value of the ROWID
pseudocolumn into that column.
SQL statements that create tables and clusters can also use ANSI data types and data types from the IBM products SQL/DS and DB2. Oracle recognizes the ANSI or IBM data type name that differs from the Oracle Database data type name. It converts the data type to the equivalent Oracle data type, records the Oracle data type as the name of the column data type, and stores the column data in the Oracle data type based on the conversions shown in the tables that follow.
Table 3-6 ANSI Data Types Converted to Oracle Data Types
ANSI SQL Data Type | Oracle Data Type |
---|---|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The NUMERIC
and DECIMAL
data types can specify only fixed-point numbers. For those data types, the scale (s
) defaults to 0.
The FLOAT
data type is a floating-point number with a binary precision b. The default precision for this data type is 126 binary, or 38 decimal.
The DOUBLE PRECISION
data type is a floating-point number with binary precision 126.
The REAL
data type is a floating-point number with a binary precision of 63, or 18 decimal.
Do not define columns with the following SQL/DS and DB2 data types, because they have no corresponding Oracle data type:
GRAPHIC
LONG
VARGRAPHIC
VARGRAPHIC
TIME
Note that data of type TIME
can also be expressed as Oracle datetime data.
See Also:
"Datetime and Interval Data Types"Table 3-7 SQL/DS and DB2 Data Types Converted to Oracle Data Types
SQL/DS or DB2 Data Type | Oracle Data Type |
---|---|
|
|
|
|
|
|
|
|
|
|
|
|
The DECIMAL
data type can specify only fixed-point numbers. For this data type, s
defaults to 0.
The FLOAT
data type is a floating-point number with a binary precision b
. The default precision for this data type is 126 binary or 38 decimal.
User-defined data types use Oracle built-in data types and other user-defined data types as the building blocks of object types that model the structure and behavior of data in applications. The sections that follow describe the various categories of user-defined types.
See Also:
Oracle Database Concepts for information about Oracle built-in data types
CREATE TYPE and the CREATE TYPE BODY for information about creating user-defined types
Oracle Database Object-Relational Developer's Guide for information about using user-defined types
Object types are abstractions of the real-world entities, such as purchase orders, that application programs deal with. An object type is a schema object with three kinds of components:
A name, which identifies the object type uniquely within that schema.
Attributes, which are built-in types or other user-defined types. Attributes model the structure of the real-world entity.
Methods, which are functions or procedures written in PL/SQL and stored in the database, or written in a language like C or Java and stored externally. Methods implement operations the application can perform on the real-world entity.
An object identifier (represented by the keyword OID
) uniquely identifies an object and enables you to reference the object from other objects or from relational tables. A data type category called REF
represents such references. A REF
data type is a container for an object identifier. REF
values are pointers to objects.
When a REF
value points to a nonexistent object, the REF
is said to be "dangling". A dangling REF
is different from a null REF
. To determine whether a REF
is dangling or not, use the condition IS
[NOT
] DANGLING
. For example, given object view oc_orders
in the sample schema oe
, the column customer_ref
is of type REF
to type customer_typ
, which has an attribute cust_email
:
SELECT o.customer_ref.cust_email FROM oc_orders o WHERE o.customer_ref IS NOT DANGLING;
An array is an ordered set of data elements. All elements of a given array are of the same data type. Each element has an index, which is a number corresponding to the position of the element in the array.
The number of elements in an array is the size of the array. Oracle arrays are of variable size, which is why they are called varrays. You must specify a maximum size when you declare the varray.
When you declare a varray, it does not allocate space. It defines a type, which you can use as:
The data type of a column of a relational table
An object type attribute
A PL/SQL variable, parameter, or function return type
Oracle normally stores an array object either in line (as part of the row data) or out of line (in a LOB), depending on its size. However, if you specify separate storage characteristics for a varray, then Oracle stores it out of line, regardless of its size. Refer to the varray_col_properties of CREATE TABLE for more information about varray storage.
A nested table type models an unordered set of elements. The elements may be built-in types or user-defined types. You can view a nested table as a single-column table or, if the nested table is an object type, as a multicolumn table, with a column for each attribute of the object type.
A nested table definition does not allocate space. It defines a type, which you can use to declare:
The data type of a column of a relational table
An object type attribute
A PL/SQL variable, parameter, or function return type
When a nested table appears as the type of a column in a relational table or as an attribute of the underlying object type of an object table, Oracle stores all of the nested table data in a single table, which it associates with the enclosing relational or object table.
Oracle provides SQL-based interfaces for defining new types when the built-in or ANSI-supported types are not sufficient. The behavior for these types can be implemented in C/C++, Java, or PL/ SQL. Oracle Database automatically provides the low-level infrastructure services needed for input-output, heterogeneous client-side access for new data types, and optimizations for data transfers between the application and the database.
These interfaces can be used to build user-defined (or object) types and are also used by Oracle to create some commonly useful data types. Several such data types are supplied with the server, and they serve both broad horizontal application areas (for example, the Any
types) and specific vertical ones (for example, the spatial types).
The Oracle-supplied types, along with cross-references to the documentation of their implementation and use, are described in the following sections:
The Any
types provide highly flexible modeling of procedure parameters and table columns where the actual type is not known. These data types let you dynamically encapsulate and access type descriptions, data instances, and sets of data instances of any other SQL type. These types have OCI and PL/SQL interfaces for construction and access.
This type contains an instance of a given type, with data, plus a description of the type. ANYDATA
can be used as a table column data type and lets you store heterogeneous values in a single column. The values can be of SQL built-in types as well as user-defined types.
This type contains a description of a given type plus a set of data instances of that type. ANYDATASET
can be used as a procedure parameter data type where such flexibility is needed. The values of the data instances can be of SQL built-in types as well as user-defined types.
See Also:
Oracle Database PL/SQL Packages and Types Reference for information on theANYTYPE
, ANYDATA
, and ANYDATASET
typesExtensible Markup Language (XML) is a standard format developed by the World Wide Web Consortium (W3C) for representing structured and unstructured data on the World Wide Web. Universal resource identifiers (URIs) identify resources such as Web pages anywhere on the Web. Oracle provides types to handle XML and URI data, as well as a class of URIs called DBURIRef
types to access data stored within the database itself. It also provides a set of types to store and access both external and internal URIs from within the database.
This Oracle-supplied type can be used to store and query XML data in the database. XMLType
has member functions you can use to access, extract, and query the XML data using XPath expressions. XPath is another standard developed by the W3C committee to traverse XML documents. Oracle XMLType
functions support many W3C XPath expressions. Oracle also provides a set of SQL functions and PL/SQL packages to create XMLType
values from existing relational or object-relational data.
XMLType
is a system-defined type, so you can use it as an argument of a function or as the data type of a table or view column. You can also create tables and views of XMLType
. When you create an XMLType
column in a table, you can choose to store the XML data in a CLOB
column, as binary XML (stored internally as a CLOB
), or object relationally.
You can also register the schema (using the DBMS_XMLSCHEMA
package) and create a table or column conforming to the registered schema. In this case Oracle stores the XML data in underlying object-relational columns by default, but you can specify storage in a CLOB
or binary XML column even for schema-based data.
Queries and DML on XMLType
columns operate the same regardless of the storage mechanism.
See Also:
Oracle XML DB Developer's Guide for information about using XMLType columnsOracle supplies a family of URI types—URIType
, DBURIType
, XDBURIType
, and HTTPURIType
—which are related by an inheritance hierarchy. URIType
is an object type and the others are subtypes of URIType
. Since URIType
is the supertype, you can create columns of this type and store DBURIType
or HTTPURIType
type instances in this column.
HTTPURIType You can use HTTPURIType
to store URLs to external Web pages or to files. Oracle accesses these files using HTTP (Hypertext Transfer Protocol).
XDBURIType You can use XDBURIType
to expose documents in the XML database hierarchy as URIs that can be embedded in any URIType
column in a table. The XDBURIType
consists of a URL, which comprises the hierarchical name of the XML document to which it refers and an optional fragment representing the XPath syntax. The fragment is separated from the URL part by a pound sign (#). The following lines are examples of XDBURIType
:
/home/oe/doc1.xml /home/oe/doc1.xml#/orders/order_item
DBURIType DBURIType
can be used to store DBURIRef
values, which reference data inside the database. Storing DBURIRef
values lets you reference data stored inside or outside the database and access the data consistently.
DBURIRef
values use an XPath-like representation to reference data inside the database. If you imagine the database as an XML tree, then you would see the tables, rows, and columns as elements in the XML document. For example, the sample human resources user hr
would see the following XML tree:
<HR> <EMPLOYEES> <ROW> <EMPLOYEE_ID>205</EMPLOYEE_ID> <LAST_NAME>Higgins</LAST_NAME> <SALARY>12008</SALARY> .. <!-- other columns --> </ROW> ... <!-- other rows --> </EMPLOYEES> <!-- other tables..--> </HR> <!-- other user schemas on which you have some privilege on..-->
The DBURIRef
is an XPath expression over this virtual XML document. So to reference the SALARY
value in the EMPLOYEES
table for the employee with employee number 205, you can write a DBURIRef
as,
/HR/EMPLOYEES/ROW[EMPLOYEE_ID=205]/SALARY
Using this model, you can reference data stored in CLOB
columns or other columns and expose them as URLs to the external world.
Oracle also provides the URIFactory
package, which can create and return instances of the various subtypes of the URITypes
. The package analyzes the URL string, identifies the type of URL (HTTP, DBURI
, and so on), and creates an instance of the subtype. To create a DBURI
instance, the URL must start with the prefix /oradb
. For example, URIFactory.getURI('/oradb/HR/EMPLOYEES')
would create a DBURIType
instance and URIFactory.getUri('/sys/schema')
would create an XDBURIType
instance.
See Also:
Oracle Database Object-Relational Developer's Guide for general information on object types and type inheritance
Oracle XML DB Developer's Guide for more information about these supplied types and their implementation
Oracle Streams Advanced Queuing User's Guide for information about using XMLType
with Oracle Advanced Queuing
Oracle Spatial is designed to make spatial data management easier and more natural to users of location-enabled applications, geographic information system (GIS) applications, and geoimaging applications. After the spatial data is stored in an Oracle Database, you can easily manipulate, retrieve, and relate it to all the other data stored in the database. The following data types are available only if you have installed Oracle Spatial.
The geometric description of a spatial object is stored in a single row, in a single column of object type SDO_GEOMETRY
in a user-defined table. Any table that has a column of type SDO_GEOMETRY
must have another column, or set of columns, that defines a unique primary key for that table. Tables of this sort are sometimes called geometry tables.
The SDO_GEOMETRY
object type has the following definition:
CREATE TYPE SDO_GEOMETRY AS OBJECT (sgo_gtype NUMBER, sdo_srid NUMBER, sdo_point SDO_POINT_TYPE, sdo_elem_info SDO_ELEM_INFO_ARRAY, sdo_ordinates SDO_ORDINATE_ARRAY); /
This type describes a topology geometry, which is stored in a single row, in a single column of object type SDO_TOPO_GEOMETRY
in a user-defined table.
The SDO_TOPO_GEOMETRY
object type has the following definition:
CREATE TYPE SDO_TOPO_GEOMETRY AS OBJECT (tg_type NUMBER, tg_id NUMBER, tg_layer_id NUMBER, topology_id NUMBER); /
In the GeoRaster object-relational model, a raster grid or image object is stored in a single row, in a single column of object type SDO_GEORASTER
in a user-defined table. Tables of this sort are called GeoRaster tables.
The SDO_GEORASTER
object type has the following definition:
CREATE TYPE SDO_GEORASTER AS OBJECT (rasterType NUMBER, spatialExtent SDO_GEOMETRY, rasterDataTable VARCHAR2(32), rasterID NUMBER, metadata XMLType); /
See Also:
Oracle Spatial Developer's Guide, Oracle Spatial Topology and Network Data Models Developer's Guide, and Oracle Spatial GeoRaster Developer's Guide for information on the full implementation of the spatial data types and guidelines for using themOracle Multimedia uses object types, similar to Java or C++ classes, to describe multimedia data. An instance of these object types consists of attributes, including metadata and the media data, and methods. The Multimedia data types are created in the ORDSYS
schema. Public synonyms exist for all the data types, so you can access them without specifying the schema name.
See Also:
Oracle Multimedia Reference for information on the implementation of these types and guidelines for using themThe ORDDoc
object type supports storage and management of any type of media data, including audio, image and video data. Use this type when you want all media to be stored in a single column.
The ORDDicom
object type supports the storage and management of Digital Imaging and Communications in Medicine (DICOM), the format universally recognized as the standard for medical imaging.
The following data types provide compliance with the ISO-IEC 13249-5 Still Image standard, commonly referred to as SQL/MM StillImage.
The SI_StillImage
object type represents digital images with inherent image characteristics such as height, width, and format.
The SI_AverageColor
object type represents a feature that characterizes an image by its average color.
The SI_ColorHistogram
object type represents a feature that characterizes an image by the relative frequencies of the colors exhibited by samples of the raw image.
Given an image divided into n
by m
rectangles, the SI_PositionalColor
object type represents the feature that characterizes an image by the n
by m
most significant colors of the rectangles.
The SI_Texture
object type represents a feature that characterizes an image by the size of repeating items (coarseness), brightness variations (contrast), and predominant direction (directionality).
The SI_FeatureList
object type is a list containing up to four of the image features represented by the preceding object types (SI_AverageColor
, SI_ColorHistogram
, SI_PositionalColor
, and SI_Texture
), where each feature is associated with a feature weight.
The Oracle Expression Filter allows application developers to manage and evaluate conditional expressions that describe users' interests in data. The Expression Filter includes the following data type:
Expression Filter uses a virtual data type called Expression
to manage and evaluate conditional expressions as data in database tables. The Expression Filter creates a column of Expression
data type from a VARCHAR2
column by assigning an attribute set to the column. This assignment enables a data constraint that ensures the validity of expressions stored in the column.
You can define conditions using the EVALUATE
operator on an Expression
data type to evaluate the expressions stored in a column for some data. If you are using Enterprise Edition, then you can also define an Expression Filter index on a column of Expression
data type to process queries using the EVALUATE
operator.
See Also:
Oracle Database Rules Manager and Expression Filter Developer's Guide for more information on the Expression Filter