SQLServer2008关于CASEWHEN CASE WHEN的两种格式
1.简单Case函数
CASE sex
WHEN '1' THEN '男'
WHEN '2' THEN '⼥'
ELSE '其他' END
2.Case搜索函数
CASE WHEN sex = '1' THEN '男'
WHEN sex = '2' THEN '⼥'
ELSE '其他' END
1).两者相⽐,Case搜索函数功能更强。
2).Case函数类似于if……else if 语句，只返回第⼀个符合条件的值，之后的部分会被忽略
例⼦：(按照指定规则分组，并计算每组⼈数)
create table #temp
(
country varchar(100),
sql sever 2008people int
)
insert into #temp
select 'A',400 union all
select 'B',2890 union all
select 'C',3490 union all
select 'D',5678 union all
select 'E',457 union all
select 'F',2345
select
CASE WHEN country='A' or country='B' THEN '1组'
WHEN country='C' or country='D' THEN '2组'
WHEN country='E' or country='F'  THEN '3组'
END 组别,SUM(people) ⼈数合计
from #temp
group by
CASE WHEN country='A' or country='B' THEN '1组'
WHEN country='C' or country='D' THEN '2组'
WHEN country='E' or country='F'  THEN '3组'
END
ps.
Order by 后也可使⽤Case when ⽤于筛选需要的排序数据
Example:
order by case when ISNULL(A.ReqDate,'')!='' then A.ReqDate else A.PlanReqDate end desc