5 Data Types

This chapter is a reference for Oracle data types used by Oracle C++ Interface applications. This information helps you to understand the conversions between internal and external representations of data that occur when you transfer data between your application and the database server.

This chapter contains these topics:

Overview of Oracle Data Types

Accurate communication between your C++ program and the Oracle database server is critical. OCCI applications can retrieve data from database tables by using SQL queries or they can modify existing data with SQL INSERT, UPDATE, and DELETE functions. To facilitate communication between the host language C++ and the database server, you must be aware of how C++ data types are converted to Oracle data types and back again.

In the Oracle database, values are stored in columns in tables. Internally, Oracle represents data in particular formats called internal data types. NUMBER, VARCHAR2, and DATE are examples of Oracle internal data types.

OCCI applications work with host language data types, or external data types, predefined by the host language. When data is transferred between an OCCI application and the database server, the data from the database is converted from internal data types to external data types.

OCCI Type and Data Conversion

OCCI defines an enumerator called Type that lists the possible data representation formats available in an OCCI application. These representation formats are called external data types. When data is sent to the database server from the OCCI application, the external data type indicates to the database server what format to expect the data. When data is requested from the database server by the OCCI application, the external data type indicates the format of the data to be returned.

For example, on retrieving a value from a NUMBER column, the program may be set to retrieve it in OCCIINT format (a signed integer format into an integer variable). Or, the client might be set to send data in OCCIFLOAT format (floating-point format) stored in a C++ float variable to be inserted in a column of NUMBER type.

An OCCI application binds input parameters to a Statement, by calling a setxxx() method (the external datatype is implicitly specified by the method name), or by calling the registerOutParam(), setDataBuffer(), or setDataBufferArray() method (the external data type is explicitly specified in the method call). Similarly, when data values are fetched through a ResultSet object, the external representation of the retrieved data must be specified. This is done by calling a getxxx() method (the external datatype is implicitly specified by the method name) or by calling the setDataBuffer() method (the external data type is explicitly specified in the method call).

Note that there are more external data types than internal data types. In some cases, a single external data type maps to a single internal data type; in other cases, many external data types map to a single internal data type. The many-to-one mapping provides you with added flexibility.

See Also:

External Data Types

Internal Data Types

The internal (built-in) data types provided by Oracle are listed in this section. A brief summary of internal Oracle data types, including description, code, and maximum size, appears in Table 5-1.

Table 5-1 Summary of Oracle Internal Data Types

Internal Data Type Maximum Size 
BFILE

4 gigabytes

 
BINARY_DOUBLE

8 bytes

 
BINARY_FLOAT

4 bytes

 
CHAR

2,000 bytes

 
DATE

7 bytes

 
INTERVAL DAY TO SECOND REF

11 bytes

 
INTERVAL YEAR TO MONTH REF

5 bytes

 
LONG

2 gigabytes (2^31-1 bytes)

 
LONG RAW

2 gigabytes (2^31-1 bytes)

 
NCHAR

2,000 bytes

 
NUMBER

21 bytes

 
NVARCHAR2

32,767 bytes

 
RAW

2000 bytes (standard), 32,767 bytes (extended)

 
REF

Not Applicable

 
BLOB

4 gigabytes

 
CLOB

4 gigabytes

 
NCLOB

4 gigabytes

 
ROWID

10 bytes

 
TIMESTAMP

11 bytes

 
TIMESTAMP WITH LOCAL TIME ZONE

7 bytes

 
TIMESTAMP WITH TIME ZONE

13 bytes

 
UROWID

4000 bytes

User-defined type (object type, VARRAY, nested table)

Not Applicable

 
VARCHAR2

4000 bytes (standard), 32,767 bytes extended

See Also:

Character Strings and Byte Arrays

You can use five Oracle internal data types to specify columns that contain either characters or arrays of bytes: CHAR, VARCHAR2, RAW, LONG, and LONG RAW.

CHAR, VARCHAR2, and LONG columns normally hold character data. RAW and LONG RAW hold bytes that are not interpreted as characters, for example, pixel values in a bitmapped graphics image. Character data can be transformed when passed through a gateway between networks. For example, character data passed between systems by using different languages (where single characters may be represented by differing numbers of bytes) can be significantly changed in length. Raw data is never converted in this way.

The database designer is responsible for choosing the appropriate Oracle internal data type for each column in a table. You must be aware of the many possible ways that character and byte-array data can be represented and converted between variables in the OCCI program and Oracle database tables.

Universal Rowid (UROWID)

The universal rowid (UROWID) is a data type that can store both the logical and the physical rowid of rows in Oracle tables and in foreign tables, such as DB2 tables accessed through a gateway. Logical rowid values are primary key-based logical identifiers for the rows of index-organized tables.

To use columns of the UROWID data type, the value of the COMPATIBLE initialization parameter must be set to 8.1 or higher.

The following OCCI_SQLT types can be bound to universal rowids:

  • OCCI_SQLT_CHR (VARCHAR2)

  • OCCI_SQLT_VCS (VARCHAR)

  • OCCI_SQLT_STR (NULL terminated string)

  • OCCI_SQLT_LVC (long VARCHAR)

  • OCCI_SQLT_AFC (CHAR)

  • OCCI_SQLT_AVC (CHARZ)

  • OCCI_SQLT_VST (string)

  • OCCI_SQLT_RDD (ROWID descriptor)

External Data Types

OCCI application communicate with the Oracle database server by using external data types. Specifically, external data types are mapped to C++ data types.

Table 5-2 lists the Oracle external data types, the C++ equivalent (what the Oracle internal data type is usually converted to), and the corresponding OCCI type. Note the following conditions:

  • In C++ Data Type column, n stands for variable length and depends on program requirements or operating system.

  • The usage of types in Statement class methods is as follows:

    • setDataBuffer() and setDataBufferArray(): Only types of the form OCCI_SQLT_xxx (for example, OCCI_SQLT_INT) in the occiCommon.h file are permitted.

    • registerOutParam(): Only types of the form OCCIxxx (for example, OCCIDOUBLE, OCCICURSOR, and so on) on the occiCommon.h file are permitted. However, there are some exceptions: OCCIANYDATA, OCCIMETADATA, OCCISTREAM, and OCCIBOOL are not permitted.

  • In the ResultSet class, only types of the form OCCI_SQLT_xxx (for example, OCCI_SQLT_INT) in the occiCommon.h file are permitted for use in setDataBuffer() and setDataBufferArray() methods.

  • The TIMESTAMP and TIMESTAMP WITH TIME ZONE data types are collectively known as datetimes. The INTERVAL YEAR TO MONTH and INTERVAL DAY TO SECOND are collectively known as intervals.

Table 5-2 External Data Types and Corresponding C++ and OCCI Types

External Data Type C++ Type OCCI Type Usage Notes

16 bit signed INTEGER

 
signed short, signed int

OCCIINT

Use with setDataBuffer(), setDataBufferArray().

32 bit signed INTEGER

 
signed int, signed long

OCCIINT

Use with setDataBuffer(), setDataBufferArray().

8 bit signed INTEGER

 
signed char

OCCIINT

Use with setDataBuffer(), setDataBufferArray().

BFILE

 
Bfile

OCCIBFILE

Use with regiserOutParam().

FBFILE

 
OCILobLocator

OCCI_SQLT_FILE

Use with setDataBuffer(), setDataBufferArray().

BLOB

 
OCILobLocator

OCCI_SQLT_BLOB

Use with setDataBuffer(), setDataBufferArray().

BLOB

 
Blob

OCCIBLOB

Use with regiserOutParam().

BOOL

 
bool

OCCIBOOL

Use with regiserOutParam().

BYTES

 
Bytes

OCCIBYTES

Use with regiserOutParam().

CHAR

 
char[n]

OCCI_SQLT_AFC

Use with setDataBuffer(), setDataBufferArray().

CHAR

 
string

OCCICHAR

Use with regiserOutParam().

CLOB

 
OCILobLocator

OCCI_SQLT_CLOB

Use with setDataBuffer(), setDataBufferArray().

CHARZ

 
char[n+1]

OCCI_SQLT_RDD

Use with setDataBuffer(), setDataBufferArray().

CLOB

 
Clob

OCCICLOB

Use with regiserOutParam().

CURSOR

 
ResultSet

OCCICURSOR

Use with regiserOutParam().

DATE

 
char[7]

OCCI_SQLT_DAT

Use with setDataBuffer(), setDataBufferArray().

DATE

 
Date

OCCIDATE

Use with regiserOutParam().

DOUBLE

 
double

OCCIDOUBLE

Use with regiserOutParam().

FLOAT

 
float, double

OCCIFLOAT

Use with setDataBuffer(), setDataBufferArray().

FLOAT

 
float

OCCIFLOAT

Use with regiserOutParam().

INT

 
int

OCCIINT

Use with regiserOutParam().

INTERVAL DAY TO SECOND

 
char[11]

OCCI_SQLT_INTERVAL_DS

Use with setDataBuffer(), setDataBufferArray().

INTERVAL YEAR TO MONTH

 
char[5]

OCCI_SQLT_INTERVAL_YM

Use with setDataBuffer(), setDataBufferArray().

INTERVALDS

 
IntervalDS

OCCIINTERVALDS

Use with regiserOutParam().

INTERVALYM

 
IntervalYM

OCCIINTERVALYM

Use with regiserOutParam().

LONG

 
char[n]

OCCI_SQLT_LNG

Use with setDataBuffer(), setDataBufferArray().

LONG RAW

 
unsigned char[n]

OCCI_SQLT_LBI

Use with setDataBuffer(), setDataBufferArray().

LONG VARCHAR

 
char[n+siezeof(integer)]

OCCI_SQLT_LVC

Use with setDataBuffer(), setDataBufferArray().

LONG VARRAW

 
unsigned char[n+siezeof(integer)]

OCCI_SQLT_LVB

Use with setDataBuffer(), setDataBufferArray().

METADATA

 
MetaData

OCCIMETADATA

Use with regiserOutParam().

NAMED DATA TYPE

 
struct

OCCI_SQLT_NTY

Use with setDataBuffer(), setDataBufferArray().

NATIVE DOUBLE

 
double

OCCIBDOUBLE

Use with setDataBuffer(), setDataBufferArray().

NATIVE DOUBLE

 
Bdouble, double

OCCIBDOUBLE

Use with regiserOutParam().

NATIVE FLOAT

 
float

OCCIBFLOAT

Use with setDataBuffer(), setDataBufferArray().

NATIVE FLOAT

 
BFloat, float

OCCIBFLOAT

Use with regiserOutParam().

null terminated STRING

 
char[n+1]

OCCI_SQLT_STR

Use with setDataBuffer(), setDataBufferArray().

NUMBER

 
unsigned char[21]

OCCI_SQLT_NUM

Use with setDataBuffer(), setDataBufferArray().

NUMBER

 
Number

OCCINUMBER

Use with regiserOutParam().

POBJECT

User defined types generated by OTT utility.

 
OCCIPOBJECT

Use with regiserOutParam().

RAW

 
unsigned char[n]

OCCI_SQLT_BIN

Use with setDataBuffer(), setDataBufferArray().

REF

 
OCIRef

OCCI_SQLT_REF

Use with setDataBuffer(), setDataBufferArray().

REF

 
Ref

OCCIREF

Use with regiserOutParam().

REFANY

 
RefAny

OCCIREFANY

Use with regiserOutParam().

ROWID

 
OCIRowid

OCCI_SQLT_RID

Use with setDataBuffer(), setDataBufferArray().

ROWID

 
Bytes

OCCIROWID

Use with regiserOutParam().

ROWID descriptor

 
OCIRowid

OCCI_SQLT_RDD

Use with setDataBuffer(), setDataBufferArray().

STRING

 
STL string

OCCISTRING

Use with regiserOutParam().

TIMESTAMP

 
char[11]

OCCI_SQLT_TIMESTAMP

Use with setDataBuffer(), setDataBufferArray().

TIMESTAMP

 
Timestamp

OCCITIMESTAMP

Use with regiserOutParam().

TIMESTAMP WITH LOCAL TIME ZONE

 
char[7]

OCCI_SQLT_TIMESTAMP_LTZ

Use with setDataBuffer(), setDataBufferArray().

TIMESTAMP WITH TIME ZONE

 
char[13]

OCCI_SQLT_TIMESTAMP_TZ

Use with setDataBuffer(), setDataBufferArray().

UNSIGNED INT

 
unsigned int

OCCIUNSIGNED_INT

Use with setDataBuffer(), setDataBufferArray().

UNSIGNED INT

 
unsigned int

OCCIUNSIGNED_INT

Use with regiserOutParam().

VARCHAR

 
char[n+sizeof( short integer)]

OCCI_SQLT_VCS

Use with setDataBuffer(), setDataBufferArray().

VARCHAR2

 
char[n]

OCCI_SQLT_CHR

Use with setDataBuffer(), setDataBufferArray().

VARNUM

 
char[22]

OCCI_SQLT_VNU

Use with setDataBuffer(), setDataBufferArray().

VARRAW

 
unsigned char[n+sizeof( short integer)]

OCCI_SQLT_VBI

Use with setDataBuffer(), setDataBufferArray().

VECTOR

 
STL vector

OCCIVECTOR

Use with regiserOutParam().

Description of External Data Types

This section provides a description for each of the external data types.

BFILE

The external data type BFILE allows read-only byte stream access to large files on the file system of the database server. A BFILE is a large binary data object stored in operating system files outside database tablespaces. These files use reference semantics. The Oracle server can access a BFILE provided the underlying server operating system supports stream-mode access to these operating system files.

BDOUBLE

The BDouble interface in OCCI encapsulates the native double data and the NULL information of a column or object attribute of the type binary_double. The OCCI methods in AnyData Class, ResultSet Class and Statement Class, and the global methods that take these class objects as parameters, use the following definition for the BDOUBLE data type:

Example 5-1 Definition of the BDOUBLE Data Type

struct BDouble 
{ 
  double value; 
  bool isNull; 
 
 BDouble() 
 { 
    isNull = false; 
    value = 0.; 
 } 
};

BFLOAT

The BFloat interface in OCCI encapsulates the native float data and the NULL information of a column or object attribute of the type binary_float. The OCCI methods in AnyData Class, ResultSet Class and Statement Class, and the global methods that take these class objects as parameters, use the following definition for the BFLOAT data type:

Example 5-2 Definition of the BFLOAT Data Type

struct BFloat 
{ 
  float value; 
  bool isNull; 
 
 BFloat() 
 { 
    isNull = false; 
    value = 0.; 
 } 
};

BLOB

The external data type BLOB stores unstructured binary large objects. A BLOB can be thought of as a bitstream with no character set semantics. BLOBs can store up to 4 gigabytes of binary data.

BLOB data types have full transactional support. Changes made through OCCI participate fully in the transaction. BLOB value manipulations can be committed or rolled back. You cannot save a BLOB locator in a variable in one transaction and then use it in another transaction or session.

CHAR

The external data type CHAR is a string of characters, with a maximum length of 2000 characters. Character strings are compared by using blank-padded comparison semantics.

CHARZ

The external data type CHARZ is similar to the CHAR data type, except that the string must be NULL terminated on input, and Oracle places a NULL terminator character at the end of the string on output. The NULL terminator serves only to delimit the string on input or output. It is not part of the data in the table.

CLOB

The external data type CLOB stores fixed-width or varying-width character data. A CLOB can store up to 4 gigabytes of character data. CLOBs have full transactional support. Changes made through OCCI participate fully in the transaction. CLOB value manipulations can be committed or rolled back. You cannot save a CLOB locator in a variable in one transaction and then use it in another transaction or session.

DATE

The external data type DATE can update, insert, or retrieve a date value using the Oracle internal seven byte date binary format, as listed in Table 5-3:

Table 5-3 Format of the DATE Data Type

Example Byte 1: Century Byte 2: Year Byte 3: Month Byte 4: Day Byte 5: Hour Byte 6: Minute Byte 7: Second

1: 01-JUN-2000, 3:17PM

120

100

6

1

16

18

1

2: 01-JAN-4712 BCE

53

88

1

1

1

1

1

Example 1, 01-JUN-2000, 3:17PM:

  • The century and year bytes (1 and 2) are in excess-100 notation. Dates BCE (Before Common Era) are less than 100. Dates in the Common Era (CE), 0 and after, are greater than 100. For dates 0 and after, the first digit of both bytes 1 and 2 signifies that it is of the CE.

  • For byte 1, the second and third digits of the century are calculated as the year (an integer) divided by 100. With integer division, the fractional portion is discarded. The following calculation is for the year 1992: 1992 / 100 = 19.

  • For byte 1, 119 represents the twentieth century, 1900 to 1999. A value of 120 would represent the twenty-first century, 2000 to 2099.

  • For byte 2, the second and third digits of the year are calculated as the year modulo 100: 1992 % 100 = 92.

  • For byte 2, 192 represents the ninety-second year of the current century. A value of 100 would represent the zeroth year of the current century.

  • The year 2000 would yield 120 for byte 1 and 100 for byte 2.

  • For bytes 3 through 7, valid dates begin at 01-JAN of the year. The month byte ranges from 1 to 12, the date byte ranges from 1 to 31, the hour byte ranges from 1 to 24, the minute byte ranges from 1 to 60, and the second byte ranges from 1 to 60.

Example 2, 01-JAN-4712 BCE:

  • For years before 0 CE, centuries and years are represented by the difference between 100 and the number.

  • For byte 1, 01-JAN-4712 BCE is century 53: 100 - 47 = 53.

  • For byte 2, 01-JAN-4712 BCE is year 88: 100 - 12 = 88.

If no time is specified for a date, the time defaults to midnight and bytes 5 through 6 are set to 1: 1, 1, 1.

When you enter a date in binary format by using the external data type DATE, the database does not perform consistency or range checking. All data in this format must be validated before input.

There is little need for the external data type DATE. It is more convenient to convert DATE values to a character format, because most programs deal with dates in a character format, such as DD-MON-YYYY. Instead, you may use the Date data type.

When a DATE column is converted to a character string in your program, it is returned in the default format mask for your session, or as specified in the INIT.ORA file.

This data type is different from OCCI DATE which corresponds to a C++ Date data type.

FLOAT

The external data type FLOAT processes numbers with fractional parts. The number is represented in the host system's floating-point format. Normally, the length is 4 or 8 bytes.

The internal format of an Oracle number is decimal. Most floating-point implementations are binary. Oracle, therefore, represents numbers with greater precision than floating-point representations.

INTEGER

The external data type INTEGER is used for converting numbers. An external integer is a signed binary number. Its size is operating system-dependent. If the number being returned from Oracle is not an integer, then the fractional part is discarded, and no error is returned. If the number returned exceeds the capacity of a signed integer for the system, then Oracle returns an overflow on conversion error.

A rounding error may occur when converting between FLOAT and NUMBER. Using a FLOAT as a bind variable in a query may return an error. You can work around this by converting the FLOAT to a string and using the OCCI type OCCI_SQLT_CHR or the OCCI type OCCI_SQLT_STR for the operation.

INTERVAL DAY TO SECOND

The external data type INTERVAL DAY TO SECOND stores the difference between two datetime values in terms of days, hours, minutes, and seconds. Specify this data type as follows:

INTERVAL DAY [(day_precision)] 
   TO SECOND [(fractional_seconds_precision)]

This example uses the following placeholders:

  • day_precision: Number of digits in the DAY datetime field. Accepted values are 1 to 9. The default is 2.

  • fractional_seconds_precision: Number of digits in the fractional part of the SECOND datetime field. Accepted values are 0 to 9. The default is 6.

To specify an INTERVAL DAY TO SECOND literal with nondefault day and second precision, you must specify the precisions in the literal. For example, you might specify an interval of 100 days, 10 hours, 20 minutes, 42 seconds, and 22 hundredths of a second as follows:

INTERVAL '100 10:20:42.22' DAY(3) TO SECOND(2)

You can also use abbreviated forms of the INTERVAL DAY TO SECOND literal. For example:

  • INTERVAL '90' MINUTE maps to INTERVAL '00 00:90:00.00' DAY TO SECOND(2)

  • INTERVAL '30:30' HOUR TO MINUTE maps to INTERVAL '00 30:30:00.00' DAY TO SECOND(2)

  • INTERVAL '30' SECOND(2,2) maps to INTERVAL '00 00:00:30.00' DAY TO SECOND(2)

INTERVAL YEAR TO MONTH

The external data type INTERVAL YEAR TO MONTH stores the difference between two datetime values by using the YEAR and MONTH datetime fields. Specify INTERVAL YEAR TO MONTH as follows:

INTERVAL YEAR [(year_precision)] TO MONTH

The placeholder year_precision is the number of digits in the YEAR datetime field. The default value of year_precision is 2. To specify an INTERVAL YEAR TO MONTH literal with a nondefault year_precision, you must specify the precision in the literal. For example, the following INTERVAL YEAR TO MONTH literal indicates an interval of 123 years, 2 months:

INTERVAL '123-2' YEAR(3) TO MONTH

You can also use abbreviated forms of the INTERVAL YEAR TO MONTH literal. For example,

  • INTERVAL '10' MONTH maps to INTERVAL '0-10' YEAR TO MONTH

  • INTERVAL '123' YEAR(3) maps to INTERVAL '123-0' YEAR(3) TO MONTH

LONG

The external data type LONG stores character strings longer than 4000 bytes and up to 2 gigabytes in a column of data type LONG. Columns of this type are only used for storage and retrieval of long strings. They cannot be used in methods, expressions, or WHERE clauses. LONG column values are generally converted to and from character strings.

LONG RAW

The external data type LONG RAW is similar to the external data type RAW, except that it stores up to 2 gigabytes.

LONG VARCHAR

The external data type LONG VARCHAR stores data from and into an Oracle LONG column. The first four bytes contain the length of the item. The maximum length of a LONG VARCHAR is 2 gigabytes.

LONG VARRAW

The external data type LONG VARRAW store data from and into an Oracle LONG RAW column. The length is contained in the first four bytes. The maximum length is 2 gigabytes.

NCLOB

The external data type NCLOB is a national character version of a CLOB. It stores fixed-width, multibyte national character set character (NCHAR), or varying-width character set data. An NCLOB can store up to 4 gigabytes of character text data.

NCLOBs have full transactional support. Changes made through OCCI participate fully in the transaction. NCLOB value manipulations can be committed or rolled back. You cannot save an NCLOB locator in a variable in one transaction and then use it in another transaction or session.

You cannot create an object with NCLOB attributes, but you can specify NCLOB parameters in methods.

NUMBER

You should not have to use NUMBER as an external data type. If you do use it, Oracle returns numeric values in its internal 21-byte binary format and expects this format on input. The following discussion is included for completeness only.

Oracle stores values of the NUMBER data type in a variable-length format. The first byte is the exponent and is followed by 1 to 20 mantissa bytes. The high-order bit of the exponent byte is the sign bit; it is set for positive numbers and it is cleared for negative numbers. The lower 7 bits represent the exponent, which is a base-100 digit with an offset of 65.

To calculate the decimal exponent, add 65 to the base-100 exponent and add another 128 if the number is positive. If the number is negative, you do the same, but subsequently the bits are inverted. For example, -5 has a base-100 exponent = 62 (0x3e). The decimal exponent is thus (~0x3e)-128-65 = 0xc1-128-65 = 193-128-65 = 0.

Each mantissa byte is a base-100 digit, in the range 1 to 100. For positive numbers, the digit has 1 added to it. So, the mantissa digit for the value 5 is 6. For negative numbers, instead of adding 1, the digit is subtracted from 101. So, the mantissa digit for the number -5 is: 101-5 = 96. Negative numbers have a byte containing 102 appended to the data bytes. However, negative numbers that have 20 mantissa bytes do not have the trailing 102 byte. Because the mantissa digits are stored in base-100, each byte can represent two decimal digits. The mantissa is normalized; leading zeroes are not stored.

Up to 20 data bytes can represent the mantissa. However, only 19 are guaranteed to be accurate. The 19 data bytes, each representing a base-100 digit, yield a maximum precision of 38 digits for an internal data type NUMBER.

Note that this data type is different from OCCI NUMBER which corresponds to a C++ Number data type.

OCCI STRING

The external data type OCCI STRING corresponds to an STL string.

OCCI VECTOR

The external data type OCCI VECTOR is used to represent collections, for example, a nested table or VARRAY. CREATE TYPE num_type as VARRAY OF NUMBER(10) can be represented in a C++ application as vector<int>, vector<Number>, and so on.

RAW

The external data type RAW is used for binary data or byte strings that are not to be interpreted or processed by Oracle. RAW could be used, for example, for graphics character sequences. The maximum length of a RAW column is 2000 bytes. If the init.ora parameter max_string_size = standard (default value), the maximum length of a RAW can be 2000 bytes. If the init.ora parameter max_string_size = extended, the maximum length of a RAW can be 32767 bytes.

When RAW data in an Oracle table is converted to a character string, the data is represented in hexadecimal code. Each byte of RAW data is represented as two characters that indicate the value of the byte, ranging from 00 to FF. If you input a character string by using RAW, then you must use hexadecimal coding.

REF

The external data type REF is a reference to a named data type. To allocate a REF for use in an application, declare a variable as a pointer to a REF.

ROWID

The external data type ROWID identifies a particular row in a database table. The ROWID is often returned from a query by issuing a statement similar to the following example:

SELECT ROWID, var1, var2 FROM db;

You can then use the returned ROWID in further DELETE statements.

If you are performing a SELECT for an UPDATE operation, then the ROWID is implicitly returned.

STRING

The external data type STRING behaves like the external data type VARCHAR2 (data type code 1), except that the external data type STRING must be NULL-terminated.

Note that this data type is different from OCCI STRING which corresponds to a C++ STL string data type.

TIMESTAMP

The external data type TIMESTAMP 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. Specify the TIMESTAMP data type as follows:

TIMESTAMP [(fractional_seconds_precision)]

The placeholder fractional_seconds_precision optionally specifies the number of digits in the fractional part of the SECOND datetime field and can be a number in the range 0 to 9. The default is 6. For example, you specify TIMESTAMP(2) as a literal as follows:

TIMESTAMP '1997-01-31 09:26:50.10'

Note that this data type is different from OCCI TIMESTAMP.

TIMESTAMP WITH LOCAL TIME ZONE

The external data type TIMESTAMP WITH TIME ZONE (TSTZ) is a variant of TIMESTAMP that includes an explicit time zone displacement in its value. The time zone displacement is the difference (in hours and minutes) between local time and Coordinated Universal Time (UTC), formerly Greenwich Mean Time. Specify the TIMESTAMP WITH TIME ZONE data type as follows:

TIMESTAMP(fractional_seconds_precision) WITH TIME ZONE

The placeholder fractional_seconds_precision optionally specifies the number of digits in the fractional part of the SECOND datetime field and can be a number in the range 0 to 9. The default is 6.

Two TIMESTAMP WITH TIME ZONE values are considered identical if they represent the same instant in UTC, regardless of the TIME ZONE offsets stored in the data.

TIMESTAMP WITH TIME ZONE

The external data type TIMESTAMP WITH TIME ZONE is a variant of TIMESTAMP that includes a time zone displacement in its value. The time zone displacement is the difference (in hours and minutes) between local time and Coordinated Universal Time (UTC), formerly Greenwich Mean Time. Specify the TIMESTAMP WITH TIME ZONE data type as follows:

TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE

The placeholder fractional_seconds_precision optionally specifies the number of digits in the fractional part of the SECOND datetime field and can be a number in the range 0 to 9. The default is 6. For example, you might specify TIMESTAMP(0) WITH TIME ZONE as a literal as follows:

TIMESTAMP '1997-01-31 09:26:50+02.00'

UNSIGNED INT

The external data type UNSIGNED INT is used for unsigned binary integers. The size in bytes is operating system dependent. The host system architecture determines the order of the bytes in a word. If the number being output from Oracle is not an integer, the fractional part is discarded, and no error is returned. If the number to be returned exceeds the capacity of an unsigned integer for the operating system, Oracle returns an overflow on conversion error.

VARCHAR

The external data type VARCHAR store character strings of varying length. The first two bytes contain the length of the character string, and the remaining bytes contain the actual string. The specified length of the string in a bind or a define call must include the two length bytes, meaning the largest VARCHAR string is 65533 bytes long, not 65535. For converting longer strings, use the LONG VARCHAR external data type.

VARCHAR2

The external data type VARCHAR2 is a variable-length string of characters up to 4000 bytes. If the init.ora parameter max_string_size = standard (default value), the maximum length of a VARCHAR2 can be 4000 bytes. If the init.ora parameter max_string_size = extended, the maximum length of a VARCHAR2 can be 32767 bytes.

VARNUM

The external data type VARNUM is similar to the external data type NUMBER, except that the first byte contains the length of the number representation. This length value does not include the length byte itself. Reserve 22 bytes to receive the longest possible VARNUM. You must set the length byte when you send a VARNUM value to the database.

Table 5-4 VARNUM Examples

Decimal Value Length Byte Exponent Byte Mantissa Bytes Terminator Byte

0

1

128

NAFoot 1 

NA

5

2

193

6

NA

-5

3

62

96

102

2767

3

194

28, 68

NA

-2767

4

61

74, 34

102

100000

2

195

11

NA

1234567

5

196

2, 24, 46, 68

NA

Footnote 1 NA means not applicable.

VARRAW

The external data type VARRAW is similar to the external data type RAW, except that the first two bytes contain the length of the data. The specified length of the string in a bind or a define call must include the two length bytes. So the largest VARRAW string that can be received or sent is 65533 bytes, not 65535. For converting longer strings, use the LONG VARRAW data type.

NATIVE DOUBLE

This external data type implements the IEEE 754 standard double-precision floating point data type. It is represented in the host system's native floating point format. The data type is stored in the Oracle Server in a byte comparable canonical format, and requires 8 bytes for storage, including the length byte. It is an alternative to Oracle NUMBER and has the following advantages over NUMBER:

  • Fewer bytes used in storage

  • Matches data types used by RDBMS Clients

  • Supports a wider range of values used in scientific calculations.

NATIVE FLOAT

This external data type implements the IEEE 754 single-precision floating point data type. It is represented in the host system's native floating point format. The data type is stored in the Oracle Server in a byte comparable canonical format, and requires 4 bytes for storage, including the length byte. It is an alternative to Oracle NUMBER and has the following advantages over NUMBER:

  • Fewer bytes used in storage

  • Matches data types used by RDBMS Clients

  • Supports a wider range of values used in scientific calculations

Data Conversions

Table 5-5 lists the supported conversions from Oracle internal data types to external data types, and from external data types to internal column representations.

Note the following conditions:

  • A REF stored in the database is converted to OCCI_SQLT_REF on output.

  • An OCCI_SQLT_REF is converted to the internal representation of a REF on input.

  • A named data type stored in the database is converted to OCCI_SQLT_NTY (and represented by a C structure in the application) on output.

  • An OCCI_SQLT_NTY (represented by a C structure in an application) is converted to the internal representation of the corresponding data type on input.

  • LOBs and BFILEs are represented by descriptors in OCCI applications, so there are no input or output conversions.

Also note that in Table 5-5, conversions have the following numeric codes:

  1. The data type must be in Oracle ROWID format for input; it is returned in Oracle ROWID format on output.

  2. The data type must be in Oracle DATE format for input; it is returned in Oracle DATE format on output.

  3. The data type must be in hexadecimal format for input; it is returned in hexadecimal format on output.

  4. The data type must represent a valid number for output.

  5. The length must be less than or equal to 2000 characters.

  6. The data type must be stored in hexadecimal format on output; it is in hexadecimal format on output.

Table 5-5 Data Conversions Between External and Internal Data Types

NAFoot 1  Internal Data Types
External Data Types VARCHAR2 NUMBER LONG ROWID DATE RAW LONG RAW CHAR BFLOAT BDOUBLE

CHAR

I/O

I/O

I/O

I/O1

I/O2

I/O3

I3, 5

I/O

I/O

I/O

CHARZ

I/O

I/O

I/O

I/O1

I/O2

I/O3

I3, 5

I/O

NA

NA

DATE

I/O

NA

I

NA

I/O

NA

NA

I/O

NA

NA

DECIMAL

I/O4

I/O

I

NA

NA

NA

NA

I/O4

NA

NA

FLOAT

I/O4

I/O

I

NA

NA

NA

NA

I/O4

I/O

I/O

INTEGER

I/O4

I/O

I

NA

NA

NA

NA

I/O4

I/O

I/O

LONG

I/O

I/O

I/O

I/O1

I/O2

I/O3

I/O3, 5

I/O

I/O

II/O

LONG RAW

O6

NA

I5, 6

NA

NA

I/O

I/O

O6

NA

NA

LONG VARCHAR

I/O

I/O

I/O

I/O1

I/O2

I/O3

I/O3, 5

I/O

I/O

I/O

LONG VARRAW

I/O6

NA

I5, 6

NA

NA

I/O

I/O

I/O6

NA

NA

NUMBER

I/O4

I/O

I

NA

NA

NA

NA

I/O4

I/O

I/O

 
OCCI BDouble

I/O

1/O

I

NA

NA

NA

NA

I/O

I/O

I/O

 
OCCI BFloat

I/O

1/O

I

NA

NA

NA

NA

I/O

I/O

I/O

OCCI Bytes

I/O6

NA

I5, 6

NA

NA

I/O

I/O

I/O6

NA

NA

OCCI Date

I/OFoot 2 

NA

I

NA

I/O

NA

NA

I/O

NA

NA

OCCI Number

I/O4

I/O

I

NA

NA

NA

NA

I/O4

I/O

I/O

OCCI Timestamp

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

RAW

I/O6

NA

I5, 6

NA

NA

I/O

I/O

I/O6

NA

NA

ROWID

I

NA

I

I/O

NA

NA

NA

I

NA

NA

STL string

I/O

I/O

I/O

I/O1

I/O2

I/O3

I/O3

-

I/O4

I/O4

STRING

I/O

I/O

I/O

I/O1

I/O2

I/O3

I/O3, 5

I/O

I/O

I/O

UNSIGNED

I/O4

I/O

I

NA

NA

NA

NA

I/O4

I/O

I/O

VARCHAR

I/O

I/O

I/O

I/O1

I/O2

I/O3

I/O3

NA

I/O

I/O

VARCHAR2

I/O

I/O

I/O

I/O1

I/O2

I/O3

I/O3, 5

I/O

I/O

I/O

VARNUM

I/O4

I/O

I

NA

NA

NA

NA

I/O4

I/O

I/O

VARRAW

I/O6

NA

I5, 6

NA

NA

I/O

I/O

I/O6

NA

NA

Footnote 1 NA means not applicable.

Footnote 2 I/O = Conversion is valid for input and output, unless otherwise specified.

Data Conversions for LOB Data Types

Table 5-6 Data Conversions for LOBs

EXTERNAL DATATYPES INTERNAL DATATYPES
CLOB BLOB

VARCHAR

I/OFoot 1 

NAFoot 2 

CHAR

I/O

NA

LONG

I/O

NA

LONG VARCHAR

I/O

NA

STL String

I/O

NA

RAW

NA

I/O

VARRAW

NA

I/O

LONG RAW

NA

I/O

LONG VARRAW

NA

I/O

OCCI Bytes

NA

I/O

Footnote 1 I/O = Conversion is valid for input and output.

Footnote 2 NA means not applicable.

See Also:

Oracle Database SecureFiles and Large Objects Developer's Guide for an introduction to LOB data types.

Data Conversions for Date, Timestamp, and Interval Data Types

You can also use a character data type for the host variable used in a fetch or insert operation from or to a datetime or interval column. Oracle performs the conversion between the character data type and datetime/interval data type for you.

Table 5-7 Data Conversions for Date, Timestamp, and Interval Data Types

External Types Internal Types
NAFoot 1  VARCHAR, CHAR DATE TS TSTZ TSLTZ INTERVAL YEAR TO MONTH INTERVAL DAY TO SECOND

VARCHAR2, CHAR

I/OFoot 2 

I/O

I/O

I/O

I/O

I/O

I/O

STL String

I/O

I/O

I/O

I/O

I/O

I/O

I/O

DATE

I/O

I/O

I/O

I/O

I/O

NA

NA

OCCI Date

I/O

I/O

I/O

I/O

I/O

NA

NA

ANSI DATE

I/O

I/O

I/O

I/O

I/O

NA

NA

TIMESTAMP (TS)

I/O

I/O

I/O

I/O

I/O

NA

NA

OCCI Timestamp

I/O

I/O

I/O

I/O

I/O

NA

NA

TIMESTAMP WITH TIME ZONE (TSTZ)

I/O

I/O

I/O

I/O

I/O

NA

NA

TIMESTAMP WITH LOCAL TIME ZONE (TSLTZ)

I/O

I/O

I/O

I/O

I/O

NA

NA

INTERVAL YEAR TO MONTH

I/O

NA

NA

NA

NA

I/O

NA

OCCI IntervalYM

I/O

NA

NA

NA

NA

I/O

NA

INTERVAL DAY TO SECOND

I/O

NA

NA

NA

NA

NA

I/O

OCCI IntervalDS

I/O

NA

NA

NA

NA

NA

I/O

Footnote 1 NA means not applicable.

Footnote 2 I/O = Conversion is valid for input and output.

These consideration apply when converting between Date, Timestamp and Interval data types:

  • When assigning a source with time zone to a target without a time zone, the time zone portion of the source is ignored. On assigning a source without a time zone to a target with a time zone, the time zone of the target is set to the session's default time zone.

  • When assigning an Oracle DATE to a TIMESTAMP, the TIME portion of the DATE is copied over to the TIMESTAMP. When assigning a TIMESTAMP to Oracle DATE, the TIME portion of the result DATE is set to zero. This is done to encourage migration of Oracle DATE to ANSI compliant DATETIME data types.

  • (When assigning an ANSI DATE to an Oracle DATE or a TIMESTAMP, the TIME portion of the Oracle DATE and the TIMESTAMP are set to zero. When assigning an Oracle DATE or a TIMESTAMP to an ANSI DATE, the TIME portion is ignored.

  • When assigning a DATETIME to a character string, the DATETIME is converted using the session's default DATETIME format. When assigning a character string to a DATETIME, the string must contain a valid DATETIME value based on the session's default DATETIME format.

  • When assigning a character string to an INTERVAL, the character string must be a valid INTERVAL character format.

  • When converting from TSLTZ to CHAR, DATE, TIMESTAMP and TSTZ, the value is adjusted to the session time zone.

  • When converting from CHAR, DATE, and TIMESTAMP to TSLTZ, the session time zone is stored in memory.

  • When assigning TSLTZ to ANSI DATE, the time portion is 0.

  • When converting from TSTZ, the time zone that the time stamp is in is stored in memory.

  • When assigning a character string to an interval, the character string must be a valid interval character format.