在SELECT FROM循環中傳遞變量

Question

我正在尋找從多個表（MainTbl）中選擇，但它將基於哪個表將被拉出的結果集（StateTbl）。

MainTables dbo.TABLE_MO，dbo.TABLE_CA，dbo.TABLE_AL，dbo.TABLE_MI

只有尋找拉基於結果集StateTbl MO，CA，WA

Declare @Loop_Count int = 0 
DECLARE @State varchar(2) 
DECLARE @SQL varchar(max) 

DECLARE db_cursor CURSOR FOR SELECT State FROM StateTbl 

OPEN db_cursor 

FETCH db_cursor INTO @State 

WHILE (@@FETCH_STATUS = 0) 
BEGIN 


SET @SQL = 
' 
    dbo.TABLE_'+ @State +' 
' 
EXEC(@SQL) 

SET @Loop_Count = @Loop_Count + 1 
FETCH db_cursor INTO @SQL 

END 
CLOSE db_cursor 
DEALLOCATE db_cursor 

Answer 1

取而代之的是循環的，你可以利用動態和StateTbl建立你動態sql。像這樣的東西。

declare @SQL nvarchar(max) = '' 

select 'select * from TABLE_' + [State] + ' UNION ALL ' 
from StateTbl 

select @SQL = left(@SQL, len(@SQL) - 10) 

select @SQL 
--uncomment the line below when you satisfied the dynamic sql is written the way you want it. 
--exec sp_executesql @SQL