千鋒教育-做有情懷、有良心、有品質的職業教育機構
1)請優化: select a.key,a.value from a where a.key not in (select b.key from b)
2)已優化: select t1.key,t1.value from ( select a.key,a.value from a ) t1 right join ( select b.key from b ) t2 on t1.key = t2 .key where t1.key is null;
3)請優化: select a.key,a.value from a where a.key in (select b.key from b)
4)已優化: select t1.key,t1.value from ( select a.key,a.value from a ) t1 join ( select b.key from b ) t2 on t1.key = t2 .key;
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