This odd little piece of code was featured in the weekly PL/SQL Challenge quiz 12 March - 18 March 2016 . What do you think will be displayed after executing the following block? DECLARE my_flag BOOLEAN; BEGIN CASE my_flag WHEN my_flag IS NULL THEN DBMS_OUTPUT.PUT_LINE ('my_flag is NULL'); WHEN TRUE THEN DBMS_OUTPUT.PUT_LINE ('my_flag is TRUE'); ELSE DBMS_OUTPUT.PUT_LINE ('my_flag is FALSE'); END CASE; END; / At first glance (if you are like me), you would say "my_flag is NULL", right? After all, my_flag is initialized to NULL when declared, and I don't change the value. But, lo and behold, you will see: my_flag is FALSE Curious, right? So what's going on? Well, we have a very confused and confusing piece of code: I have written a simple CASE (which is of the form CASE expression WHEN ...), but then my WHEN clauses follow a typical searched CASE format (CASE WHEN expr1 ... WHEN expr2 ...). CASE is a really wonderful feature in PL/SQL (and many other languages, of course), but you need to make sure you use it properly.
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