sqlserver对字段出现NULL值的处理

-判断某些字段是否为空
--case
select case when '字段名' is null then '\n' else convert(varchar(20),'字段名') end as 'newname'
select case when null is null then '\n' else convert(varchar(20),null) end as 'newname'

--sql server 2005：coalesce
select coalesce('字符串类型字段','\n') as 'newname'
select coalesce(convert(varchar(20),'非字符串类型字段'),'\n') as 'newname'
select coalesce(convert(varchar(20),null),'\n') as 'newname'

--coalesce,返回其参数中的第一个非空表达式
select coalesce(null,null,1,2,null)union
select coalesce(null,11,12,13,null)union
select coalesce(111,112,113,114,null)