在MySQL中强制对联接使用索引的语法是什么 [英] What is the syntax to force the use of an index for a join in MySQL

问题描述

在进行直接选择时使用"FORCE/USE/IGNORE INDEX"的文档已被详细记录，但是从文档中尚不清楚如何为JOIN进行操作.

The use of the "FORCE/USE/IGNORE INDEX" when doing a straightforward select is well-documented, but it's not clear from the documentation how to do it for a JOIN.

如何强制将特定索引用于联接表?

How do you force a specific index to be used for a joined table?

推荐答案

FORCE/USE/IGNORE放在您要加入的表名之后，如果使用的是别名，则在别名之后.

The FORCE/USE/IGNORE goes after the table name you are joining, and after the alias if you're using one.

SELECT
  t1.`id` AS `id_1`,
  t2.`id` AS `id_2`
FROM
  `table1` t1
LEFT OUTER JOIN
  `table2` t2
  FORCE INDEX FOR JOIN (`table1_id`)
  ON (t2.`table1_id` = t1.`id`)

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