Oracle® Database SQL Language Reference 11g Release 2 (11.2) Part Number E17118-04 |
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You can write user-defined functions in PL/SQL, Java, or C to provide functionality that is not available in SQL or SQL built-in functions. User-defined functions can appear in a SQL statement wherever an expression can occur.
For example, user-defined functions can be used in the following:
The select list of a SELECT
statement
The condition of a WHERE
clause
CONNECT
BY
, START
WITH
, ORDER
BY
, and GROUP
BY
clauses
The VALUES
clause of an INSERT
statement
The SET
clause of an UPDATE
statement
Note:
Oracle SQL does not support calling of functions with Boolean parameters or returns. Therefore, if your user-defined functions will be called from SQL statements, you must design them to return numbers (0 or 1) or character strings ('TRUE
' or 'FALSE
').The optional expression list must match attributes of the function, package, or operator.
Restriction on User-defined Functions The DISTINCT
and ALL
keywords are valid only with a user-defined aggregate function.
See Also:
CREATE FUNCTION for information on creating functions, including restrictions on user-defined functions
Oracle Database Advanced Application Developer's Guide for a complete discussion of the creation and use of user functions
User-defined functions must be created as top-level functions or declared with a package specification before they can be named within a SQL statement.
To use a user function in a SQL expression, you must own or have EXECUTE
privilege on the user function. To query a view defined with a user function, you must have SELECT
privileges on the view. No separate EXECUTE
privileges are needed to select from the view.
See Also:
CREATE FUNCTION for information on creating top-level functions and CREATE PACKAGE for information on specifying packaged functionsWithin a SQL statement, the names of database columns take precedence over the names of functions with no parameters. For example, if the Human Resources manager creates the following two objects in the hr
schema:
CREATE TABLE new_emps (new_sal NUMBER, ...);
CREATE FUNCTION new_sal RETURN NUMBER IS BEGIN ... END;
then in the following two statements, the reference to new_sal
refers to the column new_emps.new_sal
:
SELECT new_sal FROM new_emps; SELECT new_emps.new_sal FROM new_emps;
To access the function new_sal
, you would enter:
SELECT hr.new_sal FROM new_emps;
Here are some sample calls to user functions that are allowed in SQL expressions:
circle_area (radius) payroll.tax_rate (empno) hr.employees.tax_rate (dependent, empno)@remote
Example To call the tax_rate
user function from schema hr
, execute it against the ss_no
and sal
columns in tax_table
, specify the following:
SELECT hr.tax_rate (ss_no, sal)
INTO income_tax
FROM tax_table WHERE ss_no = tax_id;
The INTO
clause is PL/SQL that lets you place the results into the variable income_tax
.
If only one of the optional schema or package names is given, then the first identifier can be either a schema name or a package name. For example, to determine whether PAYROLL
in the reference PAYROLL
.TAX_RATE
is a schema or package name, Oracle Database proceeds as follows:
Check for the PAYROLL
package in the current schema.
If a PAYROLL
package is not found, then look for a schema name PAYROLL
that contains a top-level TAX_RATE
function. If no such function is found, then return an error.
If the PAYROLL
package is found in the current schema, then look for a TAX_RATE
function in the PAYROLL
package. If no such function is found, then return an error.
You can also refer to a stored top-level function using any synonym that you have defined for it.