「無效的列名稱」，訂單上的子查詢的別名

Question

我已經創建了一個存儲過程，我想添加一個替代的順序by子句。 問題是查詢失敗的「無效列名稱」aantal regels'「

這是我現在的查詢。

SELECT 
      l.lead_id, 
      l.afdeling_id, 
      l.advertentie_id, 
      l.naam, 
      l.type, 
      l.status, 
      l.herkomst, 
      l.aanmaakdatum, 
      l.klant_id, 
      l.overigegegevens, 
      af.afdelingsnaam, 
      (SELECT 
       COUNT(lead_regel_id) 
      FROM 
       Lead_regel As lr 
      Where 
       Lr.lead_id = l.lead_id And 
       lr.status <> 100 
      ) 
      AS aantal_regels, 

      (SELECT 
       COUNT(lead_id) 
      FROM 
       Lead_unread As lu 
      Where 
       lu.lead_id = l.lead_id And 
       lu.user_id = @uid 
      ) 
      As lead_ongelezen, 

      (SELECT 
       COUNT(lru.lead_regel_id) 
      FROM 
       Lead_regel As lr2 
      INNER JOIN 
       Lead_regel_unread As lru ON 
       lr2.lead_regel_id = lru.lead_regel_id 
      Where 
       lr2.lead_id = l.lead_id And 
       lru.user_id = @uid And 
       lr2.status <> 100 
      ) 
      As lead_regel_ongelezen 

     FROM 
      Lead AS l 

     INNER JOIN 
      Afdeling AS af ON 
      l.afdeling_id = af.afdeling_id 

     WHERE 
      l.afdeling_id = @aid AND 
      l.status <> 100 

     ORDER BY 
      CASE WHEN @orderby = 'default' THEN l.aanmaakdatum END DESC, 
      CASE WHEN @orderby = 'type' THEN l.type END ASC, 
      CASE WHEN @orderby = 'naam' THEN l.naam END ASC, 
      CASE WHEN @orderby = 'reacties' THEN aantal_regels END DESC 

希望有人能幫助我！

Answer 1

你不能以這種方式按別名排序。

第一個選項是重複代碼。注意：僅僅因爲你重複了代碼，SQL引擎不再那麼天真以至於再次執行它，它會重新使用結果。

ORDER BY 
    CASE WHEN @orderby = 'default' THEN l.aanmaakdatum END DESC, 
    CASE WHEN @orderby = 'type' THEN l.type END ASC, 
    CASE WHEN @orderby = 'naam' THEN l.naam END ASC, 
    CASE WHEN @orderby = 'reacties' THEN (SELECT 
              COUNT(lead_regel_id) 
             FROM 
              Lead_regel As lr 
             WHERE 
              Lr.lead_id = l.lead_id And 
              Lr.status <> 100 
             ) END DESC 

左右，它的所有使用子查詢...

SELECT 
    * 
    FROM 
    (
    yourQuery 
) 
    AS sub_query 
    ORDER BY 
     CASE WHEN @orderby = 'default' THEN aanmaakdatum END DESC, 
     CASE WHEN @orderby = 'type'  THEN type   END ASC, 
     CASE WHEN @orderby = 'naam'  THEN naam   END ASC, 
     CASE WHEN @orderby = 'reacties' THEN aantal_regels END DESC 

Answer 2

短的版本是，雖然ORDER BY本身可以使用別名很愉快，在順序CASE聲明不能。 CASE語句將作爲SELECT的一部分進行評估，因此在任何別名被考慮之前進行評估。