SQL in/not in/exists/not exists

name from student where name in(‘zhang‘,‘wang‘,‘zhao‘);

select * from A where cc in(select cc from B)　

（2）in 与 “=”的区别：

select name from student where name in(‘zhang‘,‘wang‘,‘zhao‘);

select name from student where name=‘zhang‘ or name=‘wang‘ or name=‘zhao‘

*IN 和 NOT IN并不是针对索引的，因此查询会消耗大量时间

二、EXISTX / NOT EXISTS　

SQL in/not in/exists/not exists

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