JOIN
语法说明
JOIN
用于把来自两个或多个表的行结合起来。
下图展示了 LEFT JOIN
、RIGHT JOIN
、INNER JOIN
、和 OUTER JOIN
。
SELECT [select_list] FROM TableA A LEFT JOIN TableB B ON A.Key=B.Key |
![leftjoin](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/left_join.png) |
SELECT [select_list] FROM TableA A LEFT JOIN TableB B ON A.Key=B.Key WHERE B.Key IS NULL |
![leftjoinwhere](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/left_join_where.png) |
SELECT [select_list] FROM TableA A RIGHT JOIN TableB B ON A.Key=B.Key |
![leftjoinwhere](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/right_join.png) |
SELECT [select_list] FROM TableA A RIGHT JOIN TableB B ON A.Key=B.Key WHERE A.Key IS NULL |
![leftjoinwhere](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/right_join_where.png) |
SELECT [select_list] FROM TableA A INNER JOIN TableB B ON A.Key=B.Key |
![innerjoin](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/inner_join.png) |
|
|
SELECT [select_list] FROM TableA A FULL OUTER JOIN TableB B ON A.Key=B.Key |
![leftjoin](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/full_join.png) |
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 |
![fulljoinwhere](https://community-shared-data-1308875761.cos.ap-beijing.myqcloud.com/artwork/docs/reference/full_join_where.png) |
更多信息,参考: