以如下left join查询语句为范例: select * from t1 left join t2 on t1.c=t2.a ; 以下初始化数据: 1 DROP TABLE IF EXISTS `t1`; 2 CREATE TABLE `t1` ( 3 `a` int DEFAULT NULL, 4 `b` varchar(20) DEFAULT NULL 5 ) 6 INSERT INTO `t1` VALUES (1, 'a'); 7 INSERT INTO `t1` VALUES (1,…