MySQL Bugs: #551: IF() return incorrect result

Bug #551	IF() return incorrect result
Submitted:	30 May 2003 22:22	Modified:	25 Jun 2003 23:50
Reporter:	CW WAN	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server	Severity:	S3 (Non-critical)
Version:	1.7.5	OS:	Windows (win98/win2000)
Assigned to:	Victor Vagin	CPU Architecture:	Any

Description:
using mysqlgui 1.7.5 execute

select @a:=16,@b:=7,IF(@a>=@b,@a,@b)
return 7

How to repeat:
select @a:=15,@b:=2,IF(@a>=@b,@a,@b)
return 2

select @a:=15,@b:=2,IF(@a>=@b,@a,@b)
return 2
any one can help?

There is no problem with IF() itself.

Something goes wrong when comparing two user variables.

mysql> select @a:=5 as a, @b:=2 as b, @a > @b, @a > 2, 5 > @b, @a < @b;
+---+---+---------+--------+--------+---------+
| a | b | @a > @b | @a > 2 | 5 > @b | @a < @b |
+---+---+---------+--------+--------+---------+
| 5 | 2 |       1 |      1 |      1 |       0 |
+---+---+---------+--------+--------+---------+

Sorry,
My previsous example was from 'wrong' part of testing sequence. It shos correct result. Here are two more test cases which demonstrate the bug:

# Correct result

mysql> select @a:=10,@b:=1, @a > @b, @a < @b;
+--------+-------+---------+---------+
| @a:=10 | @b:=1 | @a > @b | @a < @b |
+--------+-------+---------+---------+
|     10 |     1 |       1 |       0 |
+--------+-------+---------+---------+

# Wron result 
mysql> select @a:=10,@b:=2, @a > @b, @a < @b;
+--------+-------+---------+---------+
| @a:=10 | @b:=2 | @a > @b | @a < @b |
+--------+-------+---------+---------+
|     10 |     2 |       0 |       1 |
+--------+-------+---------+---------+

Thank you for your bug report. This issue has been fixed in the latest
development tree for that product. You can find more information about
accessing our development trees at 
    http://www.mysql.com/doc/en/Installing_source_tree.html

The reason of the bug was that mysql operated with user variable as it was string.

thanks guys!