使用OR子句的MySQL JOIN查询非常慢 [英] MySql JOIN query with OR clause very slow

问题描述

我有以下查询:

SELECT a.id, b.from, b.to FROM a INNER JOIN b ON a.id = b.from OR a.id = b.to;

，这非常慢.

如果我删除OR子句并分别运行每个查询，则两个查询将在1秒内执行.

If I remove the OR clause and run each query separately then the both queries execute under 1 second.

SELECT a.id, b.from, b.to FROM a INNER JOIN b ON a.id = b.from;
SELECT a.id, b.from, b.to FROM a INNER JOIN b ON a.id = b.to; 

如何加快原始查询(设置索引)的速度或重新设计查询本身?

How can I speed up the original query (set up indexes) or redesign the query itself?

推荐答案

使用并集怎么办?

SELECT a.id, b.from, b.to FROM a INNER JOIN b ON a.id=b.from
UNION
SELECT a.id, b.from, b.to FROM a INNER JOIN b ON a.id=b.to

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