join 的用法

1. 笛卡儿积

SELECT * FROM TABLE1 A CROSS JOIN TABLE2 B

2. 内连接

SELECT * FROM TABLE1 A INNER JOIN TABLE2 ON A.ID=B.ID WHERE A.NAME='SQL'

3. 左外连接

SELECT * FROM TABLE1 A LEFT OUTER JOIN TABLE2 ON A.ID=B.ID WHERE A.NAME='SQL'

4. 右外连接

SELECT * FROM TABLE1 A RIGHT OUTER JOIN TABLE2 B ON A.ID=B.ID WHERE A.NAME='SQL'

5. 全外连接

SELECT * FROM TABLE1 A FULL OUTER JOIN TABLE2 B ON A.ID=B.ID WHERE A.NAME<>'SQL'

6. USING

SELECT * FROM TABLE1 A INNER JOIN TABLE2 B USING (ID,NAME)

7. NATURAL

SELECT * FROM TABLE1 A NATURAL INNER JOIN TABLE2