Subprograms: subprocedures and subfunctions v16
You can use the capability and functionality of SPL procedure and function programs to your advantage to build well-structured and maintainable programs by organizing the SPL code into subprocedures and subfunctions.
You can invoke the same SPL code multiple times from different locations in a relatively large SPL program by declaring subprocedures and subfunctions in the SPL program.
Subprocedures and subfunctions have the following characteristics:
- The syntax, structure, and functionality of subprocedures and subfunctions are almost identical to standalone procedures and functions. The major difference is the use of the keyword
CREATE FUNCTIONto declare the subprogram.
- Subprocedures and subfunctions provide isolation for the identifiers (that is, variables, cursors, types, and other subprograms) declared within itself. That is, you can't access or alter these identifiers from the upper, parent-level SPL programs or subprograms outside of the subprocedure or subfunction. This ensures that the subprocedure and subfunction results are reliable and predictable.
- The declaration section of subprocedures and subfunctions can include its own subprocedures and subfunctions. Thus, a multi-level hierarchy of subprograms can exist in the standalone program. In the hierarchy, a subprogram can access the identifiers of upper-level parent subprograms and also invoke upper-level parent subprograms. However, the same access to identifiers and invocation can't be done for lower-level child subprograms in the hierarchy.
You can declare and invoke subprocedures and subfunctions from any of the following types of SPL programs:
- Standalone procedures and functions
- Anonymous blocks
- Procedure and function methods of an object type body
- Subprocedures and subfunctions declared in any of the preceding programs
creating_a_subprocedure creating_a_subfunction block_relationships invoking_subprograms using_forward_declarations overloading_subprograms accessing_subprogram_variables