Pass arguments from DB2 to external functions

DB2^® provides storage for all parameters passed to a UDF. Therefore, parameters are passed to the external function by address.

This is the normal parameter passing method for programs. For service programs, ensure that the parameters are defined correctly in the function code.

When defining and using the parameters in the UDF, care should be taken to ensure that no more storage is referenced for a given parameter than is defined for that parameter. The parameters are all stored in the same space and exceeding a given parameter's storage space can overwrite another parameter's value. This, in turn, can cause the function to see invalid input data or cause the value returned to the database to be invalid.

There are several supported parameter styles available to external UDFs. For the most part, the styles differ in how many parameters are passed to the external program or service program.

Parameter style SQL
The parameter style SQL conforms to the industry standard Structured Query Language (SQL). This parameter style can only be used with scalar UDFs.
Parameter style DB2SQL
With the DB2SQL parameter style, the same parameters and same order of parameters are passed into the external program or service program as are passed in for parameter style SQL. However, DB2SQL allows additional optional parameters to be passed along as well.
Parameter style GENERAL (or SIMPLE CALL)
With parameter style GENERAL, the parameters are passed into the external service program just as they are specified in the CREATE FUNCTION statement. This parameter style can only be used with scalar UDFs.
Parameter style GENERAL WITH NULLS
The parameter style GENERAL WITH NULLS can only be used with scalar UDFs.
Parameter style DB2GENERAL
Parameter style DB2GENERAL is used by Java™ UDFs.
Parameter style Java
The Java™ parameter style is the style specified by the SQLJ Part 1: SQL Routines standard.

Parent topic: Write UDFs as external functions