(ORDER BY CASE WHEN) 按子查询排序答案

【问题标题】：(ORDER BY CASE WHEN) ordering by subquery(ORDER BY CASE WHEN) 按子查询排序
【发布时间】：2014-02-06 05:00:07
【问题描述】：

我需要按 int 列升序对结果进行排序，但我只想获取带数字的行 (0...10000)，但默认排序会在数字之前为我提供此列的空值行。我用谷歌搜索了将带有 null 的行设置为排序末尾（毕竟是数字）的解决方案，它看起来像

SELECT ProductName
FROM Products
ORDER BY
  CASE WHEN Position is null THEN 1 ELSE 0 END,
  Position

所以我的查询看起来像：

SELECT  c.CompanyId, c.CompanyName, c.CompanyCategoryId, cc.CompanyCategoryName, c.HQCountryISO, c.CrunchBaseUrl,c.AngelListUrl, 
(SELECT MAX(mf.NumLikes) FROM MeasurementFacebook mf
JOIN FacebookAccount f ON f.CompanyId = c.CompanyId
WHERE f.FacebookAccountId in (mf.FacebookAccountId)) as Likes,
(SELECT MAX(mt.NumFollowers) FROM MeasurementTwitter mt
JOIN TwitterAccount t ON t.CompanyId = c.CompanyId
WHERE t.TwitterAccountId in (mt.TwitterAccountId)) as Followers,
(SELECT MAX(ma.AlexaRanking) FROM MeasurementAlexa ma
JOIN Website w ON w.CompanyId = c.CompanyId
WHERE w.WebsiteId in (ma.WebsiteId)) as AlexaRank
FROM Company c 
JOIN CompanyCategory cc ON c.CompanyCategoryId = cc.CompanyCategoryId 
WHERE c.HQCountryISO =  'FRA' 
ORDER BY CASE  WHEN AlexaRank IS NULL THEN 1 ELSE 0 END, AlexaRank 
OFFSET 0 ROWS FETCH NEXT 10 ROWS ONLY

如您所见，AlexaRank 是第三个子查询的结果，我想按此列排序结果。但我有一个错误，上面写着：

Msg 207, Level 16, State 1, Line 14
Invalid column name 'AlexaRank'.

我做错了什么？谢谢

【问题讨论】：

标签： sql sql-server tsql

【解决方案1】：

虽然您可以在 ORDER BY 子句中使用别名，但您不能在表达式中使用别名，最简单的解决方案是将其放在 cte/子查询中：

;WITH cte AS (SELECT  c.CompanyId
                      , c.CompanyName
                      , c.CompanyCategoryId
                      , cc.CompanyCategoryName
                      , c.HQCountryISO
                      , c.CrunchBaseUrl
                      ,c.AngelListUrl
                      ,(SELECT MAX(mf.NumLikes) 
                        FROM MeasurementFacebook mf
                        JOIN FacebookAccount f ON f.CompanyId = c.CompanyId
                        WHERE f.FacebookAccountId in (mf.FacebookAccountId)) as Likes
                      ,(SELECT MAX(mt.NumFollowers) 
                        FROM MeasurementTwitter mt
                        JOIN TwitterAccount t ON t.CompanyId = c.CompanyId
                        WHERE t.TwitterAccountId in (mt.TwitterAccountId)) as Followers
                      ,(SELECT MAX(ma.AlexaRanking) 
                        FROM MeasurementAlexa ma
                        JOIN Website w ON w.CompanyId = c.CompanyId
                        WHERE w.WebsiteId in (ma.WebsiteId)) as AlexaRank
                FROM Company c 
                JOIN CompanyCategory cc ON c.CompanyCategoryId = cc.CompanyCategoryId 
                WHERE c.HQCountryISO =  'FRA')
SELECT * 
FROM  cte
ORDER BY CASE WHEN AlexaRank IS NULL THEN 1 ELSE 0 END, AlexaRank 
OFFSET 0 ROWS FETCH NEXT 10 ROWS ONLY

【讨论】：

【解决方案2】：

非常低效的代码，但您可以执行以下操作。基本上将您的初始查询包装在一个公用表表达式中，这样您就不需要在您的 order by 中重写您的第三个子选择。

SELECT * FROM (
SELECT c.companyid, 
   c.companyname, 
   c.companycategoryid, 
   cc.companycategoryname, 
   c.hqcountryiso, 
   c.crunchbaseurl, 
   c.angellisturl, 
   (SELECT Max(mf.numlikes) 
    FROM   measurementfacebook mf 
           JOIN facebookaccount f 
             ON f.companyid = c.companyid 
    WHERE  f.facebookaccountid IN ( mf.facebookaccountid )) AS Likes, 
   (SELECT Max(mt.numfollowers) 
    FROM   measurementtwitter mt 
           JOIN twitteraccount t 
             ON t.companyid = c.companyid 
    WHERE  t.twitteraccountid IN ( mt.twitteraccountid ))   AS Followers, 
   (SELECT Max(ma.alexaranking) 
    FROM   measurementalexa ma 
           JOIN website w 
             ON w.companyid = c.companyid 
    WHERE  w.websiteid IN ( ma.websiteid ))                 AS AlexaRank 
FROM   company c 
   JOIN companycategory cc 
     ON c.companycategoryid = cc.companycategoryid 
WHERE  c.hqcountryiso = 'FRA' ) Q
ORDER  BY CASE 
        WHEN Q.AlexaRank IS NULL THEN 1 
        ELSE 0 
      END, 
      Q.AlexaRank

【讨论】：