使用变量作为动态SQL中列名的一部分

Question

我想在动态SQL语句中使用变量作为列名的一部分。

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

取决于变量@CurrentPlayerId，我想用一些数据更新相关玩家列。

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

我意识到我可以通过一系列的IF语句来实现这一点，但我希望以更清晰的方式来实现。

我有以下代码，但我认为我的转义导致了问题。我已经重新编写了这个视图时间，但我似乎无法使其工作。

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 

如果我将它作为select运行，则返回以下结果。

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·卡洛斯说得对唯一的问题是变量@CurrentPlayerId数据类型是INT，所以你需要将它转换为NVARCHAR()https://www.mssqltips.com/sqlservertip/3014/concatenation-of-different-sql-server-data-types/。

为了保持一致性，您应该已将@CurrentPlayerBetAmount标为INT。如果你这样做，那么你也需要投它。

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 

还是我的偏好，如果你打算无论如何要更改记录将只是做：

但是，你也可以简单地设置它，当如同时声明为NVARCAHR(MAX)，然后单引号的价值更新声明，如果你有4列。你也可以认为第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 
    ???? 

注意你实际上是更新整个表，你的愿望是什么？

Answer 2

不要引用变量。

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

Answer 3

说到干净的方式做到这一点，恕我直言，最好的方法是使用sp_executesql与参数，这意味着给定的代码的@CurrentPlayerId和@CurrentPlayerBetAmount输入参数：

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