1.IN子查询语法规范以及应用场景

2.NOT IN子查询

3.EXISTS子查询

4.案例代码：

示例1：IN子查询的使用

use StudentManageDB
go
--select StudentName from Students 
--where StudentId=(select StudentId from ScoreList where SQLServerDB>80)
select StudentName from Students 
where StudentId in (select StudentId from ScoreList where SQLServerDB>80)

示例2：NOT IN子查询的使用

use StudentManageDB
go
select StudentId,StudentName from Students
where StudentId not in(select StudentId from ScoreList)

示例3：EXISTS子查询的使用

use StudentManageDB
go
if exists(select * from ScoreList where CSharp<60)
   print '本次考试内容较难'
else
   print '本次考试内容适中'

--NOT EXISTS的使用
if not exists(select * from ScoreList where CSharp<60)
      print '本次考试内容适中'
else
      print '本次考试内容较难'