Seven-learn

去除重复数据

去除重复数据

比较下列代码：
select FDepartment from T_Employee
select DISTINCT FDepartment from T_Employee
DISTINCT 是对整个结果集进行数据重复处理的，而不是针对每一个列，因此下面的语句并不会保留FDepartment进行重复值处理：
select FDepartment,FSubCompany from T_Employee

相关代码：

本节代码

alter table T_Employee ADD FSubCompany varchar(20);
alter table T_Employee ADD FDepartment varchar(20);
update T_Employee set FSubCompany='Beijing',FDepartment='Development'
where FNumber='DEV001';
update T_Employee set FSubCompany='ShenZhen',FDepartment='Development'
where FNumber='DEV002';
update T_Employee set FSubCompany='Beijing',FDepartment='HumanResource'
where FNumber='HR001';
update T_Employee set FSubCompany='Beijing',FDepartment='HumanResource'
where FNumber='HR002';
update T_Employee set FSubCompany='Beijing',FDepartment='InfoTech'
where FNumber='IT001';
update T_Employee set FSubCompany='ShenZhen',FDepartment='InfoTech'
where FNumber='IT002';
update T_Employee set FSubCompany='Beijing',FDepartment='Sales'
where FNumber='SALE001';
update T_Employee set FSubCompany='Beijing',FDepartment='Sales'
where FNumber='SALE002';
update T_Employee set FSubCompany='ShenZhen',FDepartment='Sales'
where FNumber='SALE003';