Oracle IN与Exists存在差异吗? [英] Oracle IN vs Exists difference?

问题描述

我对oracle IN和EXISTS感到困惑.我有以下要求.

I am confused with oracle IN and EXISTS. I have below requirement.

我需要让所有名字都在里面的员工-

I need to get all the employees whose names are in-

select * from emp where ename in('smith','brown','john','johnson');

我可以在这里使用EXISTS吗? IN子句也有1000个限制. EXISTS也有任何这样的限制吗?

Can i use EXISTS here? Also IN clause has 1000 limitation. Does EXISTS also has any such limitation?

谢谢！

推荐答案

IN选择匹配值的列表. EXISTS返回布尔值，如true或false.存在比进入要快.

IN picks the list of matching values. EXISTS returns the boolean values like true or false. Exists is faster than in.

示例

IN

select ename from emp e where mgr in(select empno from emp where ename='KING');

存在

select ename from emp e 
  where exists (select 1 from emp where e.mgr = empno and ename = 'KING'); 

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