T-SQL 简单子查询

 

1.使用变量的方式实现的查询

1 use StudentManageDB
2 go
3 declare @StuId int
4 --查询张永利学号
5 select @StuId=StudentId from Students where StudentName='张永利'
6 --查询学号排在张永利后面的学员
7 select StudentId,StudentName,Gender,Birthday from Students
8 where StudentId>@StuId

2.简单子查询

1 use StudentManageDB
2 go
3 
4 --查询学号排在张永利后面的学员
5 select StudentId,StudentName,Gender,Birthday from Students
6 where StudentId>(select StudentId from Students where StudentName='张永利')

3.连表查询

1 use StudentManageDB
2 go
3 --使用等值连接查询
4 select StudentName from Students
5 inner join ScoreList on Students.StudentId=ScoreList.StudentId
6 where SQLServerDB>90
7 
8 select StudentId,StudentName from Students
9 select StudentId,SQLServerDB from ScoreList

4.使用连表查询替换子查询

1 use StudentManageDB
2 go
3 --使用子查询
4 select StudentName from Students
5 where StudentId=(select StudentId from ScoreList where SQLServerDB>90)

 

转载于:https://www.cnblogs.com/Spinoza/p/10047462.html