如何优化MySQL查询以进行更新? [英] How can I optimize MySQL query for update?

问题描述

我有一个包含30万条记录的表.在此表中有duplicae行，我想更新列"flag"

I have a table with 300 000 records. In this table have duplicae rows and I want to update column "flag"

表

------------------------------------
|number | flag | ... more column ...|
------------------------------------
|ABCD   |  0   | ...................|
|ABCD   |  0   | ...................|
|ABCD   |  0   | ...................|
|BCDE   |  0   | ...................|
|BCDE   |  0   | ...................|

我使用此查询来更新标志"列:

I use this query for updating "flag" column:

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，此查询的工作非常缓慢(超过600秒).

This query working very very slowly (more 600 seconds) for this 300 000 records.

如何优化此查询?

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

If "name" is duplicate I want to update flag_qty

推荐答案

如果您尚未在number上建立索引，则应添加一个-

If you do not already have an index on number you should add one -

CREATE INDEX table_number ON table (number);

更新，请尝试--

UPDATE inv t1
INNER JOIN inv t2
    ON t1.name = t2.name
    AND t1.id <> t2.id
SET t1.flag_qty = 1;

您可以直接将数据选择到另一个表中，而不用先进行此标志更新，从而仅使用重复项来创建表.

You can create your table with just the duplicates by selecting this data directly into another table instead of doing this flag update first.

INSERT INTO duplicate_invs
SELECT DISTINCT inv1.*
FROM inv AS inv1
INNER JOIN inv AS inv2
    ON inv1.name = inv2.name
    AND inv1.id < inv2.id

如果您可以解释从inv表中删除行的逻辑，则可能是整个过程可以一步完成.

If you can explain the logic for which rows get deleted from inv table it may be that the whole process can be done in one step.

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