SQL Server 2012 多表连接查询功能实例代码_MsSql_

 -- 交叉连接产生笛卡尔值 (X*Y) SELECT * FROM Student cross Join dbo.ClassInfo --另外一种写法 SELECT * FROM Student , ClassInfo -- 内连接 (Inner 可以省略) SELECT * FROM Student JOIN dbo.ClassInfo ON dbo.Student.Class = dbo.ClassInfo.ID; -- Inner Join SELECT * FROM Student INNER JOIN dbo.ClassInfo ON dbo.Student.Class = dbo.ClassInfo.ID; -- on 条件，通常是 主外键，但是不限于主外键 -- on 条件，允许有多个，而且可能是针对某个表的 SELECT * FROM Student INNER JOIN dbo.ClassInfo ON dbo.Student.Class = dbo.ClassInfo.ID AND dbo.Student.Class IN (1,2) -- 针对Student表增加查询条件 -- 不等于 (笛卡尔值减去 相等的值) SELECT * FROM Student INNER JOIN dbo.ClassInfo ON dbo.Student.Class <> dbo.ClassInfo.ID; --自连接 从Class表中查询到Class所在的系 SELECT T1.* ,T2.ClassName FROM dbo.ClassInfo AS T1 INNER JOIN dbo.ClassInfo AS T2 ON T1.PID=T2.ID -- Left Join SELECT * FROM Student Left JOIN dbo.ClassInfo ON dbo.Student.Class = dbo.ClassInfo.ID; -- Right Join SELECT * FROM Student RIGHT JOIN dbo.ClassInfo ON dbo.Student.Class = dbo.ClassInfo.ID; -- 全外连接 SELECT * FROM Student FULL OUTER JOIN dbo.ClassInfo ON dbo.Student.Class = dbo.ClassInfo.ID; -- 外连接和内连接的区别是： -- 内连接，on条件不符合的话，会过滤掉数据 -- 外连接，以保留表为主，on条件成立显示数据，否则显示NULL --Union 纵向连接 SELECT StuID,StuName,StuEnName,StuAge,StuBirthday FROM Student WHERE StuID<=2 UNION SELECT StuID,StuName,StuEnName,StuAge,StuBirthday FROM dbo.Student WHERE StuID>2 --Union 去重复 SELECT StuSex FROM Student WHERE StuID<=2 UNION SELECT StuSex FROM dbo.Student WHERE StuID>2 --Union 显示全部 SELECT StuSex FROM Student WHERE StuID<=2 UNION ALL SELECT StuSex FROM dbo.Student WHERE StuID>2 --Except 差集,排除 SELECT StuID,StuName,StuEnName,StuAge,StuBirthday FROM Student Except SELECT StuID,StuName,StuEnName,StuAge,StuBirthday FROM dbo.Student WHERE StuID<=2 --Intersect 交集 SELECT StuID,StuName,StuEnName,StuAge,StuBirthday FROM Student WHERE StuID>=2 Except SELECT StuID,StuName,StuEnName,StuAge,StuBirthday FROM dbo.Student WHERE StuID<=3