SQL学习笔记六 union联合结果集使用

联合结果集
新建临时工数据表

create table t_tempemployee (fidcardnumber varchar(20),fname varchar(20),fage int,primary key(fidcardnumber));
insert into t_tempemployee(fidcardnumber,fname,fage) values('1234567890121','sarani',33);
insert into t_tempemployee(fidcardnumber,fname,fage) values('1234567890122','tom',26);
insert into t_tempemployee(fidcardnumber,fname,fage) values('1234567890123','yalaha',38);
insert into t_tempemployee(fidcardnumber,fname,fage) values('1234567890124','tina',26);
insert into t_tempemployee(fidcardnumber,fname,fage) values('1234567890125','konkaya',29);
insert into t_tempemployee(fidcardnumber,fname,fage) values('1234567890126','fotifa',46);

union联合

select fnumber,fage from t_employee
union
select fidcardnumber,fage from t_tempemployee

union上下的查询个数和类型必须对应一致

select fnumber,fage,fdepartment from t_employee
union
select fidcardnumber,fage ,'临时工，无部门' from t_tempemployee

union默认将重复数据去掉。如果不让他去掉，则用union all

select fname from t_employee
union all
select fname from t_tempemployee