如果set ansi_nulls为off ,那么in操作会选取null列
下面两个结果集一样:set ansi_nulls on
select a.* from aa as a,bb as b where a.name=b.name
select * from aa where name in (select name from bb)
下面两个结果集一样:set ansi_nulls on
select a.* from aa as a,bb as b where a.name=b.name
select * from aa where name in (select name from bb)
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