Select 列的最大值

Question

我有这个查询，它根据一些条件选择一些字段：

 SELECT [Qty].[plant_no]
      ,[Qty].[ord_no]
      ,[Qty].[form_no]
      ,[Qty].[form_var]
      ,[Qty].[form_part]
      ,[Qty].[res_no]
      ,isnull([RFORMPARTS].[cost_center],'_') as [RFORMPARTS_cost_center]
      ,[BARTICLES].[wght_net] AS [Unit_kg]
      ,CASE
        WHEN [Qty].[qty_unit] IN ('KG','KG-C') THEN [Qty].[fb_qty]
        WHEN [Qty].[qty_unit] = 'NR' THEN [Qty].[fb_qty]*[BARTICLES].[wght_net]
        END AS [Qty_KG]
  FROM [dbo].[E00_PRD_003] AS [Qty]
  LEFT JOIN [dbo].[RFORMPARTS] as [RFORMPARTS] ON [RFORMPARTS].[form_no] =  [Qty].[form_no] AND [RFORMPARTS].[form_var] = [Qty].[form_var] and [RFORMPARTS].[form_part] = [qty].form_part
  LEFT JOIN [dbo].[BARTICLES] AS [BARTICLES] ON [BARTICLES].[art_no] = [Qty].[form_no]
  WHERE CONVERT(VARCHAR(10),[Qty].[date_start],112) >= 20180101 AND [Qty].[in_out] = '02' AND LEFT([Qty].[res_no],2) <> 'SL'

我想获得每个 [Qty].[ord_no] 和 [Qty].[form_no] 的最大 Qty.form_part 并保留所有选定的字段。 可以和group by一起做吗？ 如果是，我该怎么做？ 如果没有，还有其他方法吗？

Answer 1

如果我理解您的要求，一种选择是创建一个子查询，它返回每个ord_no和form_no对的max ，您可以使用Group By但它只会在子查询中，然后您将使用子查询的max form_part值在您的外部查询结果中，如果您只想要每个ord_no和form_no对的最大值的行，您可以向子查询的INNER JOIN添加一个条件，添加form_part值的连接，以便它加入最大值也是如此，这将过滤掉所有具有相同ord_no和form_no组合且小于最大form_part值的额外行：

 SELECT [Qty].[plant_no]
      ,[Qty].[ord_no]
      ,[Qty].[form_no]
      ,[Qty].[form_var]
      --,[Qty].[form_part] --Replaced with the subquery max
      ,[maxVals].[form_part] --Max values returned by subquery
      ,[Qty].[res_no]
      ,isnull([RFORMPARTS].[cost_center],'_') as [RFORMPARTS_cost_center]
      ,[BARTICLES].[wght_net] AS [Unit_kg]
      ,CASE
        WHEN [Qty].[qty_unit] IN ('KG','KG-C') THEN [Qty].[fb_qty]
        WHEN [Qty].[qty_unit] = 'NR' THEN [Qty].[fb_qty]*[BARTICLES].[wght_net]
        END AS [Qty_KG]
  FROM [dbo].[E00_PRD_003] AS [Qty]
  INNER JOIN --INNER JOIN the max values on the Qty table
  (
      SELECT [ord_no], [form_no], MAX([form_part]) AS [form_part]
      FROM [dbo].[E00_PRD_003]
      GROUP BY [ord_no], [form_no]
  ) AS maxVals
  ON [maxVals].[ord_no] = [Qty].[ord_no] AND [maxVals].[form_no] = [Qty].[form_no] 
  AND [maxVals].[form_part] = [Qty].[form_part] 
  LEFT JOIN [dbo].[RFORMPARTS] as [RFORMPARTS] ON [RFORMPARTS].[form_no] =  [Qty].[form_no] AND [RFORMPARTS].[form_var] = [Qty].[form_var] and [RFORMPARTS].[form_part] = [qty].form_part
  LEFT JOIN [dbo].[BARTICLES] AS [BARTICLES] ON [BARTICLES].[art_no] = [Qty].[form_no]
  WHERE CONVERT(VARCHAR(10),[Qty].[date_start],112) >= 20180101 AND [Qty].[in_out] = '02' AND LEFT([Qty].[res_no],2) <> 'SL'