标签:val arch alt wan cti ima UNC address res
合并查询结果
合并查询结果 是将多个select语句的查询结果合并到一起
union关键字,数据库会将所有的查询结果合并到一起,然后除掉相同的记录;
union all关键字,只是简单的合并到一起
前期表准备:
create table employee ( num int(50), d_id int(50), name varchar(50), age int(50), sex varchar(50), homeadd varchar(50) ); insert into employee values(1,1001,‘zhangsan‘,26,‘nan‘,‘beijing‘); insert into employee values(2,1001,‘lisi‘,24,‘nv‘,‘hunan‘); insert into employee values(3,1002,‘wangwu‘,25,‘nan‘,‘jiangsu‘); insert into employee values(4,1004,‘aric‘,15,‘nan‘,‘yingguo‘); select * from employee; create table department ( d_id int(50), d_name varchar(50), functione varchar(50), address varchar(50) ); insert into department values(1001,‘keyanbu‘,‘yanfachanpin‘,‘3lou5hao‘); insert into department values(1002,‘shengchanbu‘,‘shengchanchanp‘,‘5louyiceng‘); insert into department values(1003,‘xiaoshoubu‘,‘cehuaxiaoshou‘,‘1louxiaoshoudating‘); select * from department;
select d_id from department union select d_id from employee;
select d_id from department union all select d_id from employee;
标签:val arch alt wan cti ima UNC address res
原文地址:https://www.cnblogs.com/xiaobaibailongma/p/12093142.html