Select 列的最大值

Question

我有一个根据某些条件选择某些字段的查询：

 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] 的最大值 Qty.form_part，同时保留所有选定的字段。是否可以通过分组来做到这一点？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，其中 returns 每个 ord_no 和 form_no 对的 max，您将使用Group By 但它只会在子查询中，然后你会在你的外部查询结果中使用子查询的 max form_part 值，如果你只想要具有每个最大值的行ord_no & form_no 对，您将向子查询的 INNER JOIN 添加一个条件，添加 form_part 值的连接，以便它连接最大值为好吧，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'

Select 列的最大值

Select max value of a column

sql

select

group-by

max

where-clause