如何提示要在 MySQL 选择查询中使用的索引?

2021-12-21 00:00:00 indexing sql mysql hint

我有一个 MySQL 查询(运行 MySQL 5.0.88)，我正在尝试加快速度.基础表有多个索引，对于有问题的查询，使用了错误的索引(i_active - 16.000 行，而 i_iln - 7 行).

I have a MySQL query (running MySQL 5.0.88), which I'm trying to speed up. The underlying table has multiple indices and for the query in question, the wrong index is used (i_active - 16.000 rows, vs. i_iln - 7 rows).

我对 MySQL 不是很有经验，但读到有一个 use index 提示，它可以强制 mySQL 使用某个索引.我正在这样尝试:

I'm not very experienced with MySQL but read there is a use index hint, which can force mySQL to use a certain index. I'm trying it like this:

SELECT art.firma USE INDEX (i_iln) ...

但这会产生 MySQL 错误.

but this produces a MySQL error.

问题:
谁能告诉我我做错了什么?(除了运行 5.0.88，我无法更改.)

Question:
Can anyone tell me what I'm doing wrong? (Except running 5.0.88, which I can't change.)

推荐答案

你错过了

FROM table

正确的 SQL 应该是:

Correct SQL should be:

SELECT art.firma FROM your_table USE INDEX (i_iln) WHERE ....

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