请教关于CASE WHEN 的一个写法

[静远]

假设有四个字段A,B,C,D
当A或B为空值时，C取D的值，否则C取自己本身的值

请问用case when可以实现吗？

[dawugui]

select case when a is null or b is null then d else c end from tb

[csuxp2008]

update table_name
set c=case when (a is null or b is null) then d
else c
end

[sgtzzc]

select a,b,c=case when a is null or b is null then d else c end,d
from tb

[黄_瓜]

select c=case when a is unll or b isnull then d else c end

[sql_sf]

select a,
       b,
       c=case when a is null or b is null then d else c end
from tb

[SQL77]

select a,
       b,
       c=case when ISNULL(A,'')='' or ISNULL(B,'')='' then d else c end
from tb

[--小F--]

select a,b,case when a is null or b is null then d else c end as c from tb

[Mr_Nice]

select case when a is null or b is null then d else c end from tb

[静远]

大家的速度好快！

[GUOCHENGJUN]

select c=case 
when a is null then d 
when b is null then d 
else c end from 表名

[ICrazyBoy]

[Quote=引用 7 楼 fredrickhu 的回复:]
SQL code
select a,b,case when a is null or b is null then d else c end as c from tb
[/Quote]

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