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