研磨Mysql之SQL的JOIN

1、inner join

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

2、left join

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

3、right join

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

4、left join (带条件)

SELECT <select_list>
FROM tableA a
LEFT JOIN tableB b
ON a.key=b.key
WHERE b.key IS NULL

5、right join (带条件)

SELECT <select_list>
FROM tableA a
RIGHT JOIN tableB b
ON a.key=b.key
WHERE a.key IS NULL

6、full outer  join

SELECT <select_list>
FROM tableA a
FULL OUTER JOIN tableB b
ON a.key=b.key
7、full outer  join（带条件）

SELECT <select_list>
FROM tableA a
FULL OUTER JOIN tableB b
ON a.key=b.key
WHERE a.key IS NULL
OR b.key IS NULL