Check for nulls

Before the function returns from the evaluate() method (for UDXs), your function calls setReturnNull to set whether the return value is NULL. You configure how UDXs behave when database NULL values are encountered when you register the UDX:

RETURNS NULL ON NULL INPUT

This option specifies that the evaluate() method is not called when any of the arguments are NULL. This setting has certain performance advantages if you want to skip your function if it is passed NULL values. This is the default.

CALLED ON NULL INPUT

This option specifies that the function is called even if NULL values are encountered. If you choose this option, use the following function within the evaluate() method to confirm whether your argument is NULL:

bool isArgNull(int n)