如果在sql查询中声明

Question

无论如何，我基本上可以在sql子句中执行以下操作，（我知道语法不正确，但这不是重点，这是主意）

set rs = select title, copy, masterID from table1

//if the masterID is not 0 then instead of using the copy from table1, use the copy from table2

if masterID<>0 then set rs2 = "select copy from table2 where masterID =" & masterID copy = rs(0)

我希望这是有道理的。期待听到您的回复。谢谢！

Answer 1

我认为你想要的是：

select title, 
       case when t1.masterID <> 0 then t2.case else t1.case end as copy, 
       masterID
from table1 as t1
left join table2 as t2
    on t1.masterID = t2.masterID

Answer 2

DECLARE @masterID int
if(@masterID <> 0)
    select copy from table2 where masterId = @masterID
 else
    select title, copy, masterID from table1