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