[TOC] ## USING - USING是个缩写符号，它允许你利用特殊的情况：连接的两端都具有相同的连接列名 示例 ``` SELECT * FROM t1 INNER JOIN t2 ON t1.num = t2.num; ``` 等价于 ``` SELECT * FROM t1 INNER JOIN t2 USING (num); ```