MySQL Bugs: #12509: ROW() = ROW() doesn't handle NULL's right

Bug #12509	ROW() = ROW() doesn't handle NULL's right
Submitted:	10 Aug 2005 21:33	Modified:	24 Aug 2005 17:22
Reporter:	Michael Widenius	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server	Severity:	S3 (Non-critical)
Version:	4.1 and 5.0	OS:
Assigned to:	Oleksandr Byelkin	CPU Architecture:	Any

Description:
Currently MySQL returns NULL if any element in a ROW() comparison is NULL, even if we should return 0 if any constant doesn't match.

mysql> select row(NULL,1)=(2,0);
-> NULL

When 0 should be the correct answer

How to repeat:
Here how it should work (From SQL-99 Complete, Really, page 237)

ROW(1,1,1) = ROW(1,1,1)  -> 1
ROW(1,1,1) = ROW(1,2,1)  -> 0
ROW(1,NULL,1) = ROW(2,2,1) -> 0
ROW(1,NULL,1) =  (1,2,1) -> NULL

Suggested fix:
As this is a not critcal problem in 4.1, better to fix it only in 5.0 (assuming the patch is not trivial)

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/internals/28444

pushed to 5.0.12

Documented in 5.0.12 changelog:

<listitem><para><literal>ROW()</literal> function returned incorrect result when comparison involved <literal>NULL</literal> values. (Bug #12509)</para></listitem>