sqlserver对字段出现NULL值的处理

代码如下:

-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)