sqlserver對欄位出現NULL值的處理

複製代碼 代碼如下:-判斷某些欄位是否為空白
--case
select case when '欄位名' is null then '\N' else convert(varchar(20),'欄位名') 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('字串類型欄位','\N') as 'NewName'
select coalesce(convert(varchar(20),'非字串類型欄位'),'\N') as 'NewName'
select coalesce(convert(varchar(20),null),'\N') as 'NewName'

--coalesce,返回其參數中的第一個非空運算式
select Coalesce(null,null,1,2,null)union
select Coalesce(null,11,12,13,null)union
select Coalesce(111,112,113,114,null)