sqlserver in 和 exist 子查询

1 in 子查询

 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)

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

2.exist 子查询

 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'