sql - “列名无效”，子查询别名的排序依据

Question

我创建了一个存储过程，我想在其中添加替代 order by 子句。问题是查询在“无效的列名'aantal regels'”上失败

这是我现在的查询。

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

希望有人可以帮助我！

Answer 1

您不能以这种方式按别名排序。

第一种选择是重复代码。注意：仅仅因为您重复代码，SQL 引擎不会天真到再次执行它，它会重复使用结果。

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

或者这一切都使用子查询......

  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

简短的版本是，虽然 ORDER BY 本身可以非常愉快地使用别名，但 ORDER BY 中的 CASE 语句不能。CASE 语句将作为 SELECT 的一部分进行评估，因此在考虑任何别名之前。