在if else或case sql表達式中選擇

Question

我想在if else或case表達式中創建一個select表達式，但我無法使它工作。

我試過了下面的事情

select
(case when DateTime1 is null then select * from LogEntries where PC_TID > '2014-03-26'
else select * from LogEntries where DateTime1 > '2014-03-26' 
end) as timeSearchParam
from LogEntries

和這個

if DateTime1 is null
begin
select * from LogEntries where PC_TID > '2014-03-26' 
end
else
begin
select * from LogEntries where DateTime1 > '2014-03-26' 
end

他們都沒有工作，我只是想不通，問題是什么。

Answer 1

其中一種方法是

select * from LogEntries where PC_TID > '2014-03-26'  and DateTime1 is null
union all
select * from LogEntries where DateTime1 > '2014-03-26'  and DateTime1 is not null
order by coalesce(DateTime1 , PC_TID)

要么

select * from LogEntries 
where 
(PC_TID > '2014-03-26'  and DateTime1 is null)
or
(DateTime1 > '2014-03-26'  and DateTime1 is not null)
order by coalesce(DateTime1 , PC_TID)