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SQL programmingYou can use the HCL OneDB™ implementation of the SQL language to develop applications for HCL OneDB™ database servers.
Guide to SQL: SyntaxThe HCL OneDB™ Guide to SQL: Syntax describes the syntax of the statements, data types, expressions, operators, and built-in functions of the HCL OneDB™ dialect of the SQL language.
Other syntax segmentsThese topics describe syntax segments, which are language elements, such as database object names or optimizer directives, that appear as a subdiagram reference in the syntax diagrams of some SQL or SPL statements.
Routine modifier A routine modifier specifies characteristics of how a user-defined routine (UDR) behaves.
Modifier Descriptions
SELFUNC (C)Use the SELFUNC modifier with a C UDR to name a companion user-defined function, called a selectivity function, to the current UDR. The selectivity function provides selectivity information about the current UDR to the optimizer.
Restrictions on the SELFUNC ModifierThe selectivity function that you specify with the SELFUNC modifier has specific requirements.

Restrictions on the SELFUNC Modifier

The selectivity function that you specify with the SELFUNC modifier has specific requirements.

The selectivity function that you specify must satisfy the following criteria:

It must take the same number of arguments as the current UDR.
The data type of each argument must be SELFUNCARGS.
It must return a value of type FLOAT between 0 and 1, which represents the percentage of selectivity of the function. (1 is highly selective; 0 is not at all selective.)
It can be written in any language that the database server supports.

A user who invokes the UDR must have the Execute privilege both on that UDR and on the selectivity function that the SELFUNC modifier specifies.

Both the UDR and the selectivity function must have the same owner.

For information on how to use the mi_funcarg* functions to extract information about the arguments of a selectivity function, see the HCL OneDB™ DataBlade® API Programmer's Guide.