sql - 避免在温暖时显示重复的 Poptart 口味

Question

请查看下面的选择语句:

  SELECT 
    fc.flavorid,
    fc.flavorname,
    CASE 
      WHEN sa.flavorid IS NULL THEN 'No'
      ELSE 'Yes' END ) IsEaten
    CASE 
      WHEN t.tempid IS NULL THEN 'No' 
      ELSE 'Yes' END ) IsWarm

  FROM [poptart] p

    LEFT JOIN [diet] d ON d.Active = 1
    LEFT JOIN [toaster] ts ON p.poptartid = ts.poptartid AND d.dietname = ts.dietname
    LEFT JOIN [flavor] fl ON fl.poptartid = ts.poptartid
    LEFT JOIN [flavorcolor] fc ON fc.flavorid = fl.flavorid

    LEFT OUTER JOIN [stomach] sa ON sa.flavorid = fc.flavorid

    LEFT JOIN [poptart] p2 ON ts.poptartid = p2.poptartid
    LEFT JOIN [temp] t ON t.tempid = p2.tempid AND t.Active = 1

  GROUP BY fc.flavorid,fc.flavorname,sa.flavorid,t.tempid
  ORDER By fc.flavorname

正如您在下面看到的，这会为“berry”的每个“IsWarm”值返回一个。我只想在此列表中返回不同的 flavor 名称，但“IsWarm”字段成为一个问题，因为它可以是或否，我只想在 Yes 可用时显示 Yes，而不是 Yes 和 No 所以它不会提取重复的 flavor 名称，例如“berry”:

    flavorid  |  flavorname  |  IsEaten  |  IsWarm
      123     |    berry     |    No     |   Yes
      123     |    berry     |    No     |   No
      234     |    fudge     |    Yes    |   No
      235     |    honey     |    No     |   No

如何让这个语句只返回这个..？

  flavorid  |  flavorname  |  IsEaten  |  IsWarm
    123     |    berry     |    No     |   Yes
    234     |    fudge     |    Yes    |   No
    235     |    honey     |    No     |   No

有什么建议吗？

Answer 1

试试这个:

;WITH FlavorsList
AS
( 
    //Your query here
    SELECT 
      fc.flavorid,
      fc.flavorname,
    CASE 
      WHEN sa.flavorid IS NULL THEN 'No'
      ELSE 'Yes' END ) IsEaten
    CASE 
      WHEN t.tempid IS NULL THEN 'No' 
      ELSE 'Yes' END ) IsWarm

  FROM [poptart] p

    LEFT JOIN [diet] d ON d.Active = 1
    LEFT JOIN [toaster] ts ON p.poptartid = ts.poptartid 
                           AND d.dietname = ts.dietname
    LEFT JOIN [flavor] fl ON fl.poptartid = ts.poptartid
    LEFT JOIN [flavorcolor] fc ON fc.flavorid = fl.flavorid

    LEFT OUTER JOIN [stomach] sa ON sa.flavorid = fc.flavorid

    LEFT JOIN [poptart] p2 ON ts.poptartid = p2.poptartid
    LEFT JOIN [temp] t ON t.tempid = p2.tempid AND t.Active = 1

  GROUP BY fc.flavorid,fc.flavorname,sa.flavorid,t.tempid
)
SELECT fl.flavorid, fl.flavorname, fl.IsEaten, Max(fl.IsWarm)
FROM FlavorsList fl
GROUP BY fl.flavorid, fl.flavorname, fl.IsEaten
ORDER BY fl.flavorname

我在这里所做的是用一个查询来包装您的结果，该查询将GROUP您第一个查询的结果BY flavorid, flavorname, IsEated。使用 MAX(IsWarm) 作为聚合函数，将使 vlafors 名称的 IsWarm 值保持 DISTINCT。我使用 CTE 编写此查询只是为了简单性和可读性，但您可以将其编写为嵌套查询。