mysql——多表——合并查询结果

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;