求如何实现这样的逻辑

[ajdkjalj]

if OBJECT_ID('A') IS NOT NULL
DROP  TABLE [A]
CREATE TABLE [A](a varchar(10),b varchar(30),c varchar(20),d int)
insert into [a]
select '001' ,'aa','cc',50 union all
select '001','bb','dd',50 union all
select '003','aa','ff',100 union all
select '003','df','ff',100 

查找出a为001,b为aa,d为50的,满足的列显示,不满足的列为空,查出结果是
001 aa 50
001 null 50
null aa null

[卖水果的net]

select 
 case when a = '001' then '001' end a,
 case when b = 'aa' then 'aa' end b,
 case when d = '50' then '50' end d
from A 
where a = '001' or b = 'aa' or d = '50'
go

(4 行受影响)
a    b    d
---- ---- ----
001  aa   50
001  NULL 50
NULL aa   NULL

(3 行受影响)

[砸死牛顿的苹果]

select *
from
(
select
case when a = '001' then '001' end a,
case when b = 'aa' then 'aa' end b,
case when d = '50' then '50' end d
from A
)t
where coalesce(a,b,d) is not null
/*
a b d
001 aa 50
001 NULL 50
NULL aa NULL
*/