Description:
I repeated the following bug on different linux servers with :
bin/mysqladmin Ver 8.41 Distrib 5.0.45, for pc-linux-gnu on i686
I have the following table :
mysql> desc Buggy;
+-----------+------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+------------+------+-----+---------+----------------+
| ID | bigint(20) | NO | PRI | NULL | auto_increment |
| FLAG | tinyint(4) | YES | | NULL | |
| DATETIME1 | datetime | YES | | NULL | |
| DATETIME2 | datetime | YES | | NULL | |
+-----------+------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
With the following values :
mysql> select * from Buggy;+----+------+---------------------+---------------------+
| ID | FLAG | DATETIME1 | DATETIME2 |
+----+------+---------------------+---------------------+
| 1 | NULL | 2007-09-17 00:00:00 | 2007-09-17 23:59:00 |
| 2 | NULL | 2007-09-18 00:00:00 | 2007-09-18 23:59:00 |
| 3 | 1 | 2007-09-28 18:36:00 | 2007-09-29 00:50:00 |
| 5 | NULL | NULL | NULL |
| 4 | 1 | 2007-12-11 16:00:00 | 2007-12-12 08:00:00 |
+----+------+---------------------+---------------------+
5 rows in set (0.00 sec)
the following select gives 1 instead of 2 :
mysql> select count(*) from Buggy where date(DATETIME1)<>date(DATETIME2);+----------+
| count(*) |
+----------+
| 1 |
+----------+
1 row in set (0.00 sec)
whereas a more strict select gives the good result :
mysql> select count(*) from Buggy where date(DATETIME1)<>date(DATETIME2) AND FLAG=1;
+----------+
| count(*) |
+----------+
| 2 |
+----------+
1 row in set (0.00 sec)
The bug seems to come from ID 5 with NULL value in the datetime fields.
But a :
mysql> select count(*) from Buggy where date(DATETIME1)<>date(DATETIME2) AND DATETIME1 IS NOT NULL;
+----------+
| count(*) |
+----------+
| 1 |
+----------+
1 row in set (0.00 sec)
still gives a bad answer
But when we delete the null value record :
mysql> delete from Buggy where DATETIME1 IS NULL;
Query OK, 1 row affected (0.00 sec)
the original select becomes good :
mysql> select count(*) from Buggy where date(DATETIME1)<>date(DATETIME2);
+----------+
| count(*) |
+----------+
| 2 |
+----------+
1 row in set (0.00 sec)
How to repeat:
See up.
Here a mysqldump of the script database/table creation
-- MySQL dump 10.11
--
-- Host: localhost Database: bug
-- ------------------------------------------------------
-- Server version 5.0.45
/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
/*!40103 SET TIME_ZONE='+00:00' */;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0
*/;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
--
-- Current Database: `bug`
--
/*!40000 DROP DATABASE IF EXISTS `bug`*/;
CREATE DATABASE /*!32312 IF NOT EXISTS*/ `bug` /*!40100 DEFAULT CHARACTER SET la
tin1 */;
USE `bug`;
--
-- Table structure for table `Buggy`
--
DROP TABLE IF EXISTS `Buggy`;
CREATE TABLE `Buggy` (
`ID` bigint(20) NOT NULL auto_increment,
`FLAG` tinyint(4) default NULL,
`DATETIME1` datetime default NULL,
`DATETIME2` datetime default NULL,
PRIMARY KEY (`ID`)
) ENGINE=MyISAM AUTO_INCREMENT=6 DEFAULT CHARSET=latin1;
--
-- Dumping data for table `Buggy`
--
LOCK TABLES `Buggy` WRITE;
/*!40000 ALTER TABLE `Buggy` DISABLE KEYS */;
INSERT INTO `Buggy` (`ID`, `FLAG`, `DATETIME1`, `DATETIME2`) VALUES (1,NULL,'200
7-09-17 00:00:00','2007-09-17 23:59:00'),(2,NULL,'2007-09-18 00:00:00','2007-09-
18 23:59:00'),(3,1,'2007-09-28 18:36:00','2007-09-29 00:50:00'),(5,NULL,NULL,NUL
L),(4,1,'2007-12-11 16:00:00','2007-12-12 08:00:00');
/*!40000 ALTER TABLE `Buggy` ENABLE KEYS */;
UNLOCK TABLES;
/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;
/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
-- Dump completed on 2007-09-14 7:43:07
