vsql/Vertica：Select 组前 5 行

Question

我有这个查询，它应该获取分组数据的前 n 行。我将 RANK() 与 OVER PARTITION BY 结合使用来确定每个组的前 n 行：

SELECT X.USERID, X.ARTID, X.AVGTIMEONPAGE,EDP.ARTDSC,
RANK() OVER (PARTITION BY X.USERID ORDER BY X.AVGTIMEONPAGE DESC) as rank
FROM
(SELECT GANG.userID AS USERID,GANG.avgTimeOnPage AS AVGTIMEONPAGE,   
split_part(GANG.pageTitle,' -',1) as ARTID
FROM GoogleAnalytics.navigazioneG AS GANG
WHERE GANG.pagePath LIKE '%DataSheets%' ) AS X
LEFT JOIN ESPDDS.ESP_DPRODUCT AS EDP
ON EDP.ARTID=X.ARTID AND EDP.SCD_IS_CURRENT=1
AND EDP.COMPANYID=1
WHERE X.ARTID NOT LIKE '%Company%' AND rank in (1,2,3,4,5)

它给我一个错误，说排名列不存在。如果我评论 WHERE 子句的最后一部分，我可以看到列排名计算正确。

谢谢

Answer 1

错误的原因是 rank 别名在同一级别不可用。请注意，使用 dense_rank 函数，因为在出现平局时不会跳过数字。

SELECT USERID,ARTID, AVGTIMEONPAGE,ARTDSC,RANK
FROM
(SELECT GANG.userID AS USERID
       ,GANG.avgTimeOnPage AS AVGTIMEONPAGE
       ,split_part(GANG.pageTitle,' -',1) as ARTID
       ,RANK() OVER (PARTITION BY X.USERID ORDER BY X.AVGTIMEONPAGE DESC) as rank   
FROM GoogleAnalytics.navigazioneG AS GANG
LEFT JOIN ESPDDS.ESP_DPRODUCT AS EDP ON EDP.ARTID=X.ARTID AND EDP.SCD_IS_CURRENT=1
AND EDP.COMPANYID=1
WHERE GANG.pagePath LIKE '%DataSheets%'
) T 
WHERE ARTID NOT LIKE '%Company%' AND rank <= 5

Answer 2

WHERE 子句在 SELECT 子句之前被求值。所以当时rank是未知的。您可以使用进一步的子查询来访问它：

SELECT *
FROM
(
  SELECT 
    X.USERID, 
    X.ARTID, 
    X.AVGTIMEONPAGE,
    EDP.ARTDSC,
    RANK() OVER (PARTITION BY X.USERID ORDER BY X.AVGTIMEONPAGE DESC) as rank
  FROM
  (
    SELECT 
      GANG.userID AS USERID,
      GANG.avgTimeOnPage AS AVGTIMEONPAGE,   
      split_part(GANG.pageTitle,' -',1) as ARTID
    FROM GoogleAnalytics.navigazioneG AS GANG
    WHERE GANG.pagePath LIKE '%DataSheets%' 
  ) AS X
  LEFT JOIN ESPDDS.ESP_DPRODUCT AS EDP ON EDP.ARTID = X.ARTID
                                      AND EDP.SCD_IS_CURRENT = 1 
                                      AND EDP.COMPANYID = 1
  WHERE X.ARTID NOT LIKE '%Company%' 
) ranked
WHERE rank in (1,2,3,4,5);

vsql/Vertica：Select 组前 5 行

vsql/Vertica: Select top 5 rows by group

sql

vertica