Bug #64054 Double negation (!!) not working in 5.5.19
Submitted: 17 Jan 2012 20:46 Modified: 18 Jan 2012 5:15
Reporter: Mike Pomraning Email Updates:
Status: Duplicate Impact on me:
None 
Category:MySQL Server: DML Severity:S1 (Critical)
Version:5.5.19 OS:Linux (i686 2.6.18)
Assigned to: CPU Architecture:Any

[17 Jan 2012 20:46] Mike Pomraning 
Description:
Under 5.5.19, "double bang" (!!) produces an incorrect result, equivalent to a single ! operator.  By contrast, 5.0 behaves properly.

mysql> SELECT VERSION(), CASE !!0 WHEN !(!0) THEN 'Yeah! :)' ELSE 'Oh, no! :(' END AS `Does ``!!0 = !(!0)``?`;
+-----------+---------------------+
| VERSION() | Does `!!0 = !(!0)`? |
+-----------+---------------------+
| 5.5.19    | Oh, no! :(          |
+-----------+---------------------+
1 row in set (0.00 sec)

How to repeat:
INCORRECT:

$ mysql -e 'SELECT VERSION(), !0, !!0, !(!0)\G'
*************************** 1. row ***************************
VERSION(): 5.5.19
       !0: 1
      !!0: 1
    !(!0): 0

CORRECT:

$ mysql -e 'SELECT VERSION(), !0, !!0, !(!0)\G'
*************************** 1. row ***************************
VERSION(): 5.0.77
       !0: 1
      !!0: 0
    !(!0): 0
[17 Jan 2012 21:47] Peter Laursen 
5.1.60 == 5.5.x

Peter
(not a MySQL person)
[18 Jan 2012 5:15] Valeriy Kravchuk 
This is a duplicate of bug #55477.