MySQL认为子查询不是在派生的！ [英] MySQL thinks subquery is derived when it is not!

问题描述

EXPLAIN SELECT node_id 
          FROM node 
         WHERE person_id IN (SELECT person_id 
                               FROM user 
                              WHERE is_locked = 0);

MySql的结果告诉我子查询是派生的.但这不是！

Results in MySql telling me the subquery is derived. But it's not!

(我知道可以很容易地将其重写为JOIN，但是我想知道为什么MySQL认为这是一个依赖的子查询.)

(I know this could easily be re-written as a JOIN, but I want to know why MySQL thinks this is a dependent subquery.)

推荐答案

这是MySQL查询优化器中的错误.看起来，如果子查询中的表与主查询中的表匹配，则即使显然不应该将其视为从属子查询，也没有容易解决的方法.对不起;参加吧.

This is a bug in the MySQL Query Optimizer. It would seem that, if the table in the subquery matches the table in the main query, it is considered a dependent subquery even if it obviously should not be, and there's no easy fix. Sorry; go for the join.

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