Join的7中状况

1、左外链接

　　SELECT * FROM A LEFT JOIN B ON A.KEY = B.KEY

　　

 

2、右外链接　

　　SELECT * FROM A RIGHT JOIN B ON A.KEY = B.KEY

　　

 

3、内链接　

　　SELECT * FROM A INNER JOIN B ON A.KEY = B.KEY

　　

 

4、全链接　

1　　SELECT * FROM A FULL OUTER JOIN B ON A.KEY = B.KEY #Mysql不支持

　　

 

2　　SELECT * FROM A LEFT JOIN B ON A.KEY=B.KEY
　　 UNION
　　 SELECT * FROM A RIGHT JOIN B ON A.KEY=B.KEY

 

5、左链接

　　SELECT * FROM A LEFT JOIN B ON A.KEY = B.KEY WHERE B.KEY IS NULL

 　　

 

6、右链接

　　SELECT * FROM A RIGHT JOIN B ON A.KEY = B.KEY WHERE A.KEY IS NULL

 　　

 

7、全外链接

　1　SELECT * FROM A FULL OUTER JOIN B ON A.KEY = B.KEY WHERE A.KEY IS NULL OR B.KEY IS NULL #mysql不支持

 　　

　　

2　　SELECT * FROM A LEFT JOIN B ON A.KEY=B.KEY WHERE B.KEY IS NULL 　　　UNION 　　 SELECT * FROM A RIGHT JOIN B ON A.KEY=B.KEY WHERE A.KEY IS NULL