计算列如何成为where字句的条件？

[wallis]

select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb from test where bb=‘1’
这样sqlserver会报错无效的列

请指点下

[billpu]

外面套一个

[黄_瓜]

select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb
from test
where (case aa when 1 then '1' when 2 then '2' when 3 then '3' end)='1'

这样

[dawugui]

[Quote=引用楼主 的回复:]
select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb from test where bb=‘1’
这样sqlserver会报错无效的列

请指点下
[/Quote]

你这样的查询貌似没有用,不如直接:

select '1' as bb from test where aa = 1

[xuam]

select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb from test where (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) =‘1’

[billpu]

select * from (select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb from test) c where bb=‘1’

[Felixzhaowenzhong]

select * from (
select case aa when 1 then '1' when 2 then '2' when 3 then '3' else ''end as bb from test
)a where bb='1' 

[xuam]

select *  from 
select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb 
where bb='1'

[dawugui]

--你这样的查询貌似没有用,不如直接:
select '1' as bb from test where aa = 1

--如果想对这个计算列做运算,可如下:
--1.用子查询
select * from
(
select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb from test
) t
where bb = ...

--2.在条件中把计算列再写一次:
select (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) as bb from test
where (case aa when 1 then '1' when 2 then '2' when 3 then '3' end) = ...