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
代码如下:
CREATE TABLE T_TempEmployee (FIdCardNumber VARCHAR(20),FName VARCHAR(20),FAge int,PRIMARY KEY(FIdCardNumber));
INSERT INTO T_TempEmployee(FIdCardNumber,FName,FAge) VALUES('12345670121','Sarani',33);
INSERT INTO T_TempEmployee(FIdCardNumber,FName,FAge) VALUES('12345670122','Tom',26);
INSERT INTO T_TempEmployee(FIdCardNumber,FName,FAge) VALUES('12345670123','Yalaha',38);
INSERT INTO T_TempEmployee(FIdCardNumber,FName,FAge) VALUES('12345670124','Tina',26);
INSERT INTO T_TempEmployee(FIdCardNumber,FName,FAge) VALUES('12345670125','Konkaya',29);
INSERT INTO T_TempEmployee(FIdCardNumber,FName,FAge) VALUES('12345670126','Fotifa',46);

Union联合
代码如下:
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
代码如下:
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
代码如下:
select FName from T_Employee
union all
select FName from T_TempEmployee