本文介绍了使用OR子句的MySQL JOIN查询非常慢的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
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更多推荐
使用OR子句的MySQL JOIN查询非常慢
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