“無效的列名稱”，“子查詢的別名上的排序依據”

Question

我已經創建了一個存儲過程，我想在其中添加一個替代order by子句。 問題是查詢失敗了“無效的列名''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

希望有人可以幫助我！

Answer 1

你不能以這種方式通過別名訂購。

第一種選擇是重復代碼。 注意：僅僅因為重復代碼，SQL引擎並不是那么天真再次執行它，它會重用結果。

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

或者全部使用子查詢......

  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

簡短的版本是，雖然ORDER BY本身可以非常愉快地使用別名，但ORDER BY中的CASE語句卻不能。 CASE語句將作為SELECT的一部分進行評估，因此在考慮任何別名之前。