MySQL 并集、交集、差集

创建两个表

CREATE TABLE `object_a` (  `id` bigint(20) NOT NULL AUTO_INCREMENT,  `oname` varchar(50) DEFAULT NULL,  `odesc` varchar(50) DEFAULT NULL,  `create_time` datetime DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1

添加数据

CREATE TABLE `object_b` (  `id` bigint(20) NOT NULL AUTO_INCREMENT,  `oname` varchar(50) DEFAULT NULL,  `odesc` varchar(50) DEFAULT NULL,  `create_time` datetime DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1

添加数据

查询并集（union all）

SELECT oname,odesc FROM object_aUNION ALLSELECT oname,odesc FROM object_b

结果如下

查询并集（union）

SELECT oname,odesc FROM object_aUNIONSELECT oname,odesc FROM object_b

结果如下

PS：union自带去重

查询交集

SELECT a.oname,a.odesc FROM object_a a INNER JOIN object_b b ON a.oname=b.oname AND a.odesc=b.odesc

等价于

SELECT a.oname,a.odesc FROM object_a a INNER JOIN object_b b USING(oname,odesc)

结果如下

PS：别的数据库可以试试这种写法

SELECT oname,odesc FROM object_a INTERSECTSELECT oname,odesc FROM object_b 

查询差集

SELECT a.oname, a.odesc FROM  object_a a   LEFT JOIN object_b b     ON a.oname = b.oname     AND a.odesc = b.odesc WHERE b.id IS NULL 

结果如下

PS：别的数据库可以试试这种写法

SELECT a.oname, a.odesc FROM object_a a MINUS SELECT b.oname, b.odesc FROM object_b b