sql中in和exists的区别效率问题 转
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不一样的条件是比不了的。
IN 适合内小外大的查询
Exists 适合内大外小的查询
Select distinct deptName from Department
where exists(select * from Employee where empGender=1)
Select distinct deptName from Department
where deptID in(select FDeptID from Employee where empGender=1)
IN 适合内小外大的查询
Exists 适合内大外小的查询
Select distinct deptName from Department
where exists(select * from Employee where empGender=1)
Select distinct deptName from Department
where deptID in(select FDeptID from Employee where empGender=1)
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