CREATE FUNCTION name ( [ ftype [, ...] ] )
RETURNS rtype
AS path
LANGUAGE 'langname'
The name of a function to create.
The data type of function arguments.
The return data type.
May be either an SQL-query or an absolute path to an object file.
may be 'C', 'sql', 'internal' or 'plname', where 'plname' is the name of a created procedural language. See CREATE LANGUAGE for details.
This is returned if the command completes successfully.
CREATE FUNCTION allows a Postgres user to register a function with a database. Subsequently, this user is treated as the owner of the function.
Refer to the chapter on functions in the PostgreSQL Programmer's Guide for further information.
Use DROP FUNCTION to drop user-defined functions.
To create a simple SQL function:
CREATE FUNCTION one() RETURNS int4
AS 'SELECT 1 AS RESULT'
LANGUAGE 'sql';
SELECT one() AS answer;
answer
------
1
To create a C function, calling a routine from a user-created shared library. This particular routine calculates a check digit and returns TRUE if the check digit in the function parameters is correct. It is intended for use in a CHECK contraint.
CREATE FUNCTION ean_checkdigit(bpchar, bpchar) RETURNS bool
AS '/usr1/proj/bray/sql/funcs.so' LANGUAGE 'c';
CREATE TABLE product
(
id char(8) PRIMARY KEY,
eanprefix char(8) CHECK (eanprefix ~ '[0-9]{2}-[0-9]{5}')
REFERENCES brandname(ean_prefix),
eancode char(6) CHECK (eancode ~ '[0-9]{6}'),
CONSTRAINT ean CHECK (ean_checkdigit(eanprefix, eancode))
);
A C function cannot return a set of values.
CREATE FUNCTION is a Postgres language extension.
SQL/PSM CREATE FUNCTION has the following syntax:Note: PSM stands for Persistent Stored Modules. It is a procedural language and it was originally hoped that PSM would be ratified as an official standard by late 1996. As of mid-1998, this has not yet happened, but it is hoped that PSM will eventually become a standard.
CREATE FUNCTION name
( [ [ IN | OUT | INOUT ] parm type [, ...] ] )
RETURNS rtype
LANGUAGE 'langname'
ESPECIFIC routine
SQL-statement