Uses of a C UDR

The following table summarizes the tasks that a C UDR can perform. It also describes where you can find additional information for each of these UDR uses.

Type of UDR	Purpose	More information
Cast function	A UDR that converts one data type to another	Write a cast function
Cost function	A UDR that determines the cost of execution for an expensive UDR	Write selectivity and cost functions
End-user routine	A UDR that performs some common task for an end user	Write an end-user routine
Iterator function	A function that returns more than one row of data	Write an iterator function
Opaque-type support function	One of a group of user-defined functions that tell the database server how to handle the data of an opaque data type	Create an Opaque Data Type
Operator-class function	User-defined functions that define operators to use with a particular secondary access method	See your access-method documentation.
Negator function	A user-defined function that calculates the Boolean NOT operation for a particular operator or function.	implementing a negator function with a C user-defined function
Selectivity function	A UDR that determines the percentage of rows likely to be returned by an expensive UDR	Write selectivity and cost functions
Parallelizable UDR	A UDR that can run in parallel when executed within a PDQ statement	Creating parallelizable UDRs
User-defined aggregate	A function that calculates an aggregate value on a particular column or value	Write an aggregate function