MySql---where---in条件过多致使的效率缓慢问题的优化方法

更新一张表中的某些记录值，更新条件来自另外一张表(数据量大)，效率极其低下。优化 update A set A.a = 0 where A.b in ( select distinct B.b from B where B.c = 0 ); 优化后code update A set A.a = 0 where A.b in ( select b from (select distinct B

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