MySql---where---in條件過多致使的效率緩慢問題的優化方法

更新一張表中的某些記錄值，更新條件來自另外一張表(數據量大)，效率極其低下。優化 update A set A.a = 0 where A.b in ( select distinct B.b from B where B.c = 0 ); 優化後code update A set A.a = 0 where A.b in ( select b from (select distinct B

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