4.MySQL常见的几种连接

1、内连接（交集部分）

SELECT <select_list>
FROM b
INNER JOIN b
ON a.key=b.key

2、

      

SELECT <select_list>
FROM b
LEFT JOIN b
ON a.key=b.key

3、

 

SELECT <select_list>
FROM b
RIGHT JOIN b
ON a.key=b.key

4、 

SELECT <select_list>
FROM b
LEFT JOIN b
ON a.key=b.key
WHERE b.key is null;

5、 

 

SELECT <select_list>
FROM b
RIGHT JOIN b
ON a.key=b.key
WHERE a.key is null;

6、

SELECT <select_list>
FROM a
FULL JOIN b
ON a.key=b.key

 

7、 

 

SELECT <select_list>
FROM a
RIGHT JOIN b
ON a.key=b.key
WHERE a.key is null
OR b.key is null;