case when和sum case when 写法及拼接字段
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2016-06-03
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case when
写法及拼接字段
2016-05-26 00:343 人阅读评论(0)收藏编辑删除
分类：
sql
版权声明：本文为博主原创文章，未经博主允许不得转载。
1 , case when 用法
select (case orderStatus
when 0 then 'A'
when 1 then 'B'
when 2 then 'C'
else 'D'
end ) as '类型',count(*) as '数量'
from table
group by orderType
2, sum case when 用法
select
sum(case orderStatus when 0 then 1 else 0 end) as 'A' ,
sum(case orderStatus when 1 then 1 else 0 end ) as 'B',
sum(case orderStatus when 2 then 1 else 0 end) as 'C',
from table
3 ,拼接字段
select(select count(1) from tableA where orderStatus=0) as 'A',
(select count(1) from tableB where orderStatus=1) as 'B',
(select count(1) from tableC where orderStatus=2) as 'C'
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