從光標

Question

返回一個表請參考下面的代碼：

DECLARE @ID int 
DECLARE @errorflag int 

DECLARE Warning_Cursor CURSOR FOR 
    SELECT TOP 3 ID FROM Warnings 
    SET @errorflag = @errorflag + @@Error 
    OPEN Warning_cursor 
     SET @errorflag = @errorflag + @@Error 
     FETCH NEXT FROM Warning_cursor INTO @ID 
     WHILE @@FETCH_STATUS = 0 
    begin 
     SELECT @ID 
     FETCH NEXT FROM Warning_cursor INTO @ID 
    END 
CLOSE Warning_cursor 
DEALLOCATE Warning_cursor 

光標返回三個表，每個一行。我怎樣才能返回一個三行的表？

Answer 1

爲什麼你不只是做，

SELECT TOP 3 ID FROM Warnings 

---

更一般地，如果你使用的是光標，你可能做錯了。

---

如果你真的必須使用遊標的原因不是問題的一部分。你可以做

DECLARE @Id int; 
DECLARE @Ids TABLE (Id Int); 
DECLARE Warning_Cursor CURSOR FOR SELECT TOP 3 ID FROM Warnings; 
OPEN Warning_cursor; 
FETCH NEXT FROM Warning_cursor INTO @Id; 
WHILE @@FETCH_STATUS = 0 BEGIN 
    INSERT @Ids SELECT @Id; 

    FETCH NEXT FROM Warning_cursor INTO @Id; 
END 
CLOSE Warning_cursor; 
DEALLOCATE Warning_cursor; 
SELECT Id FROM @Ids; 

Answer 2

答案是創建一個臨時表如下：

DECLARE @ID int 
DECLARE @errorflag int 
DECLARE @CONCATRESULT TABLE (ID INT) 
DECLARE Warning_Cursor CURSOR FOR 
    SELECT TOP 3 ID FROM Warnings 
    SET @errorflag = @errorflag + @@Error 
    OPEN Warning_cursor 
     SET @errorflag = @errorflag + @@Error 
     FETCH NEXT FROM Warning_cursor INTO @ID 
     WHILE @@FETCH_STATUS = 0 
    begin 
     INSERT into @CONCATRESULT (ID) VALUES (@ID) 
     FETCH NEXT FROM Warning_cursor INTO @ID 
    END 
CLOSE Warning_cursor 
DEALLOCATE Warning_cursor 
select id from @CONCATRESULT