SQL查詢返回，如果結果發現否則繼續查詢，直到結束行

Question

我有10個表中的SQL，並從表中獲得記錄，其中id與UNION ALL匹配;但我的問題，結果發現查詢停止進一步處理;就像c＃函數中的return語句一樣＃

Answer 1

如果你打算繼續使用UNION ALL是不可能的。

爲什麼不一次做出選擇並在每次選擇後檢查，如果您有所需的信息？如果是這樣，結束它，如果沒有，繼續並做另一個選擇。

Answer 2

IF (exists(select 1 from table1 where condition)) 
    select col1, col2 from table1 
    where condition 
else if(exists(select 1 from table2 where condition)) 
    select col1, col2 from table2 
    where condition 
else if(exists(select 1 from table3 where condition)) 
    select col1, col2 from table3 
    where condition 
... continue until table10 

Answer 3

select ... from T1 where ... 
if @@RowCount = 0 
    select ... from T2 where ... 
if @@RowCount = 0 
    select ... from T3 where ... 

如果你需要對結果做額外的處理，你既可以SELECT INTO臨時表或INSERT/SELECT到表變量。

編輯：基於來自OP的評論，可能我建議：

declare @Table1 as Table (Id Int) 
declare @Table2 as Table (Id Int) 
declare @Table3 as Table (Id Int) 
declare @Result as Table (Id Int, Source VarChar(10)) 

-- Try changing the following line to use different tables and values. 
insert into @Table2 (Id) values (42) 

insert into @Result 
    select Id, 'Table1' from @Table1 where Id = 42 
if @@RowCount = 0 
    insert into @Result 
    select Id, 'Table2' from @Table2 where Id = 42 
if @@RowCount = 0 
    insert into @Result 
    select Id, 'Table3' from @Table3 where Id = 42 

select * from @Result