使用變量作爲動態SQL中列名的一部分

Question

我想在動態SQL語句中使用變量作爲列名的一部分。

我有4列，稱爲Player1Action,Player2Action,Player3Action和Player4Action。

取決於變量@CurrentPlayerId，我想用一些數據更新相關玩家列。

因此，例如，如果CurrentPlayerId包含1，則更新列Player1Action。

我意識到我可以通過一系列的IF語句來實現這一點，但我希望以更清晰的方式來實現。

我有以下代碼，但我認爲我的轉義導致了問題。我已經重新編寫了這個視圖時間，但我似乎無法使其工作。

DECLARE 
@CurrentPlayerId INT, 
@CurrentPlayerBetAmount nvarchar(MAX), 
@stmt nvarchar(MAX); 

SET @CurrentPlayerId = 1 
SET @CurrentPlayerBetAmount = 100 

SET @stmt = N'UPDATE HandCurrent SET ''Player'' ''+'' @CurrentPlayerId ''+'' ''Action'' = 1 '','' ''Player'' ''+'' @CurrentPlayerId ''+'' ''ActionSize'' = @CurrentPlayerBetAmount' 

EXECUTE sp_executesql @stmt 

如果我將它作爲select運行，則返回以下結果。

UPDATE HandCurrent SET 'Player' '+' @CurrentPlayerId '+' 'Action' = 1 ',' 'Player' '+' @CurrentPlayerId '+' 'ActionSize' = @CurrentPlayerBetAmount 

Answer 1

DECLARE 
@CurrentPlayerId INT, 
@CurrentPlayerBetAmount INT, 
@stmt nvarchar(MAX); 

SET @CurrentPlayerId = 1 
SET @CurrentPlayerBetAmount = 100 

SET @stmt = N'UPDATE HandCurrent SET 
      Player' + CAST(@CurrentPlayerId AS NVARCHAR(10)) + 'Action = 1, 
      Player' + CAST(@CurrentPlayerId AS NVARCHAR(10)) + 'ActionSize = ' 
      + CAST(@CurrentPlayerBetAmount AS NVARCHAR(10)) 

EXECUTE sp_executesql @stmt 

胡安·卡洛斯說得對唯一的問題是變量@CurrentPlayerId數據類型是INT，所以你需要將它轉換爲NVARCHAR()https://www.mssqltips.com/sqlservertip/3014/concatenation-of-different-sql-server-data-types/。

爲了保持一致性，您應該已將@CurrentPlayerBetAmount標爲INT。如果你這樣做，那麼你也需要投它。

DECLARE 
@CurrentPlayerId NVARCHAR(MAX), 
@CurrentPlayerBetAmount NVARCHAR(MAX), 
@stmt nvarchar(MAX); 

SET @CurrentPlayerId = '1' 
SET @CurrentPlayerBetAmount = '100' 

SET @stmt = N'UPDATE HandCurrent SET 
      Player' + @CurrentPlayerId + 'Action = 1, 
      Player' + @CurrentPlayerId + 'ActionSize = ' + @CurrentPlayerBetAmount 

EXECUTE sp_executesql @stmt 

還是我的偏好，如果你打算無論如何要更改記錄將只是做：

但是，你也可以簡單地設置它，當如同時聲明爲NVARCAHR(MAX)，然後單引號的價值更新聲明，如果你有4列。你也可以認爲第n正常化，使列排....

DECLARE @CurrentPlayerId INT = 1 
DECLARE @CurrentPlayerBetAmount INT = 100 

UPDATE HandCurrent 
    Player1Action = CASE WHEN @CurrentPlayerId = 1 THEN 1 ELSE PlayerAction1 END 
    ,Player1ActionSize = CASE WHEN @CurrentPlayerId = 1 THEN @CurrentPlayerBetAmount ELSE Player1ActionSize END 
    ,Player2Action = CASE WHEN @CurrentPlayerId = 2 THEN 1 ELSE PlayerAction2 END 
    ,Player2ActionSize = CASE WHEN @CurrentPlayerId = 2 THEN @CurrentPlayerBetAmount ELSE Player2ActionSize END 
    ,Player3Action = CASE WHEN @CurrentPlayerId = 3 THEN 1 ELSE PlayerAction3 END 
    ,Player3ActionSize = CASE WHEN @CurrentPlayerId = 3 THEN @CurrentPlayerBetAmount ELSE Player3ActionSize END 
    ,Player4Action = CASE WHEN @CurrentPlayerId = 4 THEN 1 ELSE PlayerAction4 END 
    ,Player4ActionSize = CASE WHEN @CurrentPlayerId = 4 THEN @CurrentPlayerBetAmount ELSE Player4ActionSize END 
WHERE 
    ???? 

注意你實際上是更新整個表，你的願望是什麼？

Answer 2

不要引用變量。

SET @stmt = N'UPDATE HandCurrent SET 
      Player' + @CurrentPlayerId + 'Action = 1, 
      Player' + @CurrentPlayerId + 'ActionSize = ' + @CurrentPlayerBetAmount 

Answer 3

說到乾淨的方式做到這一點，恕我直言，最好的方法是使用sp_executesql與參數，這意味着給定的代碼的@CurrentPlayerId和@CurrentPlayerBetAmount輸入參數：

Declare @sql nvarchar(256) 
    , @sql1 nvarchar(256) = N'update HandCurrent 
    Set Player1Action =@value, 
    Player1ActionSize =@size' 
    , @sql2 nvarchar(256) = N'update HandCurrent 
    Set Player2Action =@value, 
    Player2ActionSize =@size' 
    , @params nvarchar (128) 
    , @CurrentPlayerId int 
    ; 

Select @sql = case @CurrentPlayerId when 1 then @sql1 when 2 then @sql2 else '' end; 
If @sql <> '' begin 
    set @params = N'@value int, @size int'; 
    execute sp_executesql @sql, @params, 
     @value =1, 
     @size = @CurrentPlayerBetAmount 
     ; 
End