sql case when问题~

[wwdpiano]

比如数据库有2列 userid username
想查询这2列 其中 如果username为null 则用'-'代替

select case username when () then '-' else username from table

()中的要怎么填？ 我试了好几种方式都不对。。。。。。求教~~~~~~

[jiao3630]

isnull()

[唵嘛呢叭咪吽]

select case when username is null then '-' else username end from table

[Spade_J]

select isnull(userid,'-'),username
from tb

[dawugui]

[Quote=引用楼主 wwdpiano 的回复:]
比如数据库有2列 userid username
想查询这2列 其中 如果username为null 则用'-'代替

select case username when () then '-' else username from table

()中的要怎么填？ 我试了好几种方式都不对。。。。。。求教~~~~~~
[/Quote]
select isnull(username,'-') username from table

[Shawn]

CREATE TABLE #temp
(
	userid INT IDENTITY,
	username VARCHAR(10)
)
INSERT #temp
SELECT 'a' UNION ALL SELECT NULL
go
--SQL:
SELECT 
	userid,
	username = CASE WHEN username IS NULL THEN '-' ELSE username END
FROM #temp
/*
1	a
2	-
*/

[Spade_J]

select userid,isnull(username,'-')
from table

[--小F--]

select
  case when username is null then '-' else  username end
from
 table


select 
  isnull(username,'-')
from
  table

[xuam]

select userid, username = case when null then '-' else username end from T

[jiao3630]

  select 
  userid,
   case when username IS null 
  then '-' 
  else username 
  end
  from tb
  
  
   select 
  userid,
   ISNULL(username,'-')
  from tb

[棉花棒棒糖]

select
userid,
case when username IS null
then '-'
else username
end
from tb


select
userid,
ISNULL(username,'-')
from tb

[tengjian1981]

select (case when username is null then '-' else username end) as UserName from table

[yubofighting]

[Quote=引用 3 楼 spade_j 的回复:]
select isnull(userid,'-'),username
from tb
[/Quote]

+++++