Example: Square of a number UDF

In this example, suppose that you want a function that returns the square of a number.

The query statement is:

SELECT SQUARE(myint) FROM mytable

Note: By using the code examples, you agree to the terms of the Code license and disclaimer information.

The following examples show how to define the UDF several different ways.

Use an SQL function

The CREATE FUNCTION statement:

CREATE FUNCTION SQUARE( inval INT) RETURNS INT
LANGUAGE SQL
SET OPTION DBGVIEW=*SOURCE
BEGIN
RETURN(inval*inval);
END

This creates an SQL function that you can debug.

Use an external function, parameter style SQL

The CREATE FUNCTION statement:

CREATE FUNCTION SQUARE(INT) RETURNS INT CAST FROM FLOAT
LANGUAGE C
EXTERNAL NAME 'MYLIB/MATH(SQUARE)'
DETERMINISTIC
NO SQL
NO EXTERNAL ACTION
PARAMETER STYLE SQL
ALLOW PARALLEL

The code:

void SQUARE(int *inval,
double *outval,
short *inind,
short *outind,
char *sqlstate,
char *funcname,
char *specname,
char *msgtext)
	{
if (*inind<0)
	  *outind=-1;
	else
	  {
	   *outval=*inval;
	   *outval=(*outval)*(*outval);
	   *outind=0;
	  }
	return;
	}

To create the external service program so it can be debugged:

CRTCMOD MODULE(mylib/square) DBGVIEW(*SOURCE)
CRTSRVPGM SRVPGM(mylib/math) MODULE(mylib/square)
		EXPORT(*ALL) ACTGRP(*CALLER)

Use an external function, parameter style GENERAL

The CREATE FUNCTION statement:

CREATE FUNCTION SQUARE(INT) RETURNS INT CAST FROM FLOAT
LANGUAGE C
EXTERNAL NAME 'MYLIB/MATH(SQUARE)'
DETERMINISTIC
NO SQL
NO EXTERNAL ACTION
PARAMETER STYLE GENERAL
ALLOW PARALLEL

The code:

double SQUARE(int *inval)
{
  double outval;
  outval=*inval;
  outval=outval*outval;
	return(outval);
	}

To create the external service program so it can be debugged:

CRTCMOD MODULE(mylib/square) DBGVIEW(*SOURCE)

   CRTSRVPGM SRVPGM(mylib/math) MODULE(mylib/square)
		EXPORT(*ALL) ACTGRP(*CALLER)