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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Create user-defined routines
Write a user-defined routineThis section outlines some implementation issues for C user-defined routines (UDRs). This section also describes the specific features and tasks of a C UDR.
Code a C UDRWhen you code a C UDR, you define routine parameters, obtain argument values, define a return value, and code the routine body to write a C function.
Define a return value
Return multiple values
The statement-local variableWhen you call a user-defined function that has an OUT parameter, you must declare a statement-local variable (SLV) in the WHERE clause of the SQL statement. The SLV holds the value that the OUT parameter returns. Other parts of the SQL statement can then access the OUT parameter value through the SLV.

The statement-local variable

When you call a user-defined function that has an OUT parameter, you must declare a statement-local variable (SLV) in the WHERE clause of the SQL statement. The SLV holds the value that the OUT parameter returns. Other parts of the SQL statement can then access the OUT parameter value through the SLV.

For example, the following SELECT statement calls the out_test() function (which the code fragment in The statement-local variable defines) and saves the result of the OUT parameter in a statement-local variable named weight:

SELECT title, weight FROM mytab
   WHERE out_test(title, 'aaa', weight # INTEGER);

The SELECT statement specifies the statement-local variable in its select list so it can return the value of the OUT parameter.

For more information about the syntax and use of SLVs, see the description of how to return multiple values from a function in the Informix® User-Defined Routines and Data Types Developer's Guide.

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