sql case when 语句处理Null

case columnName  就能判断该字段不为Null.
例如

create table test(id int identity,username varchar(20))
go
insert into test(username) values('张三')
go
insert into test(username) values('李四')
go
insert into test(username) values(null)
go
insert into test(username) values(null)
--eg.
select case username when username then username else '无名氏' end as username from test

 

结果如下

 

1	张三
2	李四
3	无名氏
4	无名氏