我有一个包含 300 000 条记录的表。在此表中有重复的行,我想更新列“flag”
TABLE
------------------------------------
|number | flag | ... more column ...|
------------------------------------
|ABCD | 0 | ...................|
|ABCD | 0 | ...................|
|ABCD | 0 | ...................|
|BCDE | 0 | ...................|
|BCDE | 0 | ...................|
我使用此查询来更新“flag”列:
UPDATE table i
INNER JOIN (SELECT number FROM table
GROUP BY number HAVING count(number) > 1 ) i2
ON i.number = i2.number
SET i.flag = '1'
对于这 300 000 条记录,此查询运行速度非常非常慢(超过 600 秒)。
我怎样才能优化这个查询?
我的桌子的结构
CREATE TABLE IF NOT EXISTS `inv` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`pn` varchar(10) NOT NULL COMMENT 'Part Number',
`qty` int(5) NOT NULL,
`qty_old` int(5) NOT NULL,
`flag_qty` tinyint(1) NOT NULL,
`name` varchar(60) NOT NULL,
`vid` int(11) NOT NULL ,
`flag_d` tinyint(1) NOT NULL ,
`flag_u` tinyint(1) NOT NULL ,
`timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
KEY `pn` (`pn`),
KEY `name` (`name`),
KEY `vid` (`vid`),
KEY `pn_2` (`pn`),
KEY `flag_qty` (`flag_qty`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=0 ;
如果“名称”重复,我想更新 flag_qty