-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)