# G-4240: Always use a CASE instead of a NVL2 command if parameter 2 or 3 of NVL2 is either a function call or a SELECT statement.

Critical

Efficiency, Reliability

## Reason

The nvl2 function always evaluates all parameters before deciding which one to use. This can be harmful, if parameter 2 or 3 is either a function call or a select statement, as they will be executed regardless of whether parameter 1 contains a null value or not.

 1 2 3 select nvl2(dummy, my_package.expensive_nn(value_in => dummy), my_package.expensive_null(value_in => dummy)) from dual; 
 1 2 3 4 5 6 7 select case when dummy is null then my_package.expensive_null(value_in => dummy) else my_package.expensive_nn(value_in => dummy) end from dual;