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


复制代码 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(‘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


复制代码 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


复制代码 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


复制代码 代码如下:

select FName from T_Employee

union all

select FName from T_TempEmployee