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，但是我無法使其工作。

我已經試過了如下因素

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 

這

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 

他們沒有工作，我只是想不通，是什麼問題。

Answer 1

的方法之一是

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) 

或

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)