Question

请查看以下选择声明：

  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

如下所示，这为'berry'的每个'IsWarm'值返回一个。我只希望在此列表中返回不同的风味名称，但是'IsWarm'字段会成为一个问题，因为它可以是是或否我想只显示是，如果是可用，不是是和否所以它不会拉出重复的名字，比如'berry'：

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

如何使此语句仅返回此内容？？

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

任何建议？

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

我在这里完成的工作是使用GROUP来自您的第一个查询BY flavorid, flavorname, IsEated的结果的查询来包装结果。使用MAX(IsWarm)作为聚合函数，会为vlafors名称保留IsWarm值DISTINCT。我使用 CTE 编写此查询只是为了简单和可读性，但您可以将其编写为嵌套查询。

避免在温暖时显示重复的Poptart Flavors

1 个答案: