How Oracle 10g evaluates NULL in boolean expressions
Boolean operations with NULL value in Oracle return UNKNOWN - not true or false. So you have something like this:
If( not(UNKNOWN and (true)) = if not( UNKNOWN) =if( UNKNOWN )In this case, IF will treat UNKNOWN as false.
If i_relaunch can be null, then you need to use some of NULL handling functions(NVL, NVL2, NULLIF, COALESCE, LNNVL) to be sure that you have correct result.
See these article for more information:
- Nulls: Nothing to Worry About
- Fundamentals of PL/SQL. Scroll down to -
Handling Null Values in Comparisons and Conditional Statements