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OVER（PARTITION BY id）を使用して個別の値をカウントする

OVER(PARTITION BY id)などのウィンドウ関数と組み合わせて個別の値をカウントすることは可能ですか？現在、私のクエリは次のとおりです。

SELECT congestion.date, congestion.week_nb, congestion.id_congestion,
   congestion.id_element,
ROW_NUMBER() OVER(
    PARTITION BY congestion.id_element
    ORDER BY congestion.date),
COUNT(DISTINCT congestion.week_nb) OVER(
    PARTITION BY congestion.id_element
) AS week_count
FROM congestion
WHERE congestion.date >= '2014.01.01'
AND congestion.date <= '2014.12.31'
ORDER BY id_element, date

しかし、クエリを実行しようとすると、次のエラーが発生します。

"COUNT(DISTINCT": "DISTINCT is not implemented for window functions"
postgresqlwindow-functions
17
user007

いいえ、エラーメッセージに示されているように、DISTINCTはWindows関数では実装されていません。 このリンク からの情報をあなたのケースに適用すると、次のようなものを使用できます：

WITH uniques AS (
 SELECT congestion.id_element, COUNT(DISTINCT congestion.week_nb) AS unique_references
 FROM congestion
WHERE congestion.date >= '2014.01.01'
AND congestion.date <= '2014.12.31'
 GROUP BY congestion.id_element
)

SELECT congestion.date, congestion.week_nb, congestion.id_congestion,
   congestion.id_element,
ROW_NUMBER() OVER(
    PARTITION BY congestion.id_element
    ORDER BY congestion.date),
uniques.unique_references AS week_count
FROM congestion
JOIN uniques USING (id_element)
WHERE congestion.date >= '2014.01.01'
AND congestion.date <= '2014.12.31'
ORDER BY id_element, date

状況によっては、サブクエリをSELECT- listに直接入れることもできます。

SELECT congestion.date, congestion.week_nb, congestion.id_congestion,
   congestion.id_element,
ROW_NUMBER() OVER(
    PARTITION BY congestion.id_element
    ORDER BY congestion.date),
(SELECT COUNT(DISTINCT dist_con.week_nb)
    FROM congestion AS dist_con
    WHERE dist_con.date >= '2014.01.01'
    AND dist_con.date <= '2014.12.31'
    AND dist_con.id_element = congestion.id_element) AS week_count
FROM congestion
WHERE congestion.date >= '2014.01.01'
AND congestion.date <= '2014.12.31'
ORDER BY id_element, date
6
Simo Kivistö

最も簡単な方法は、サブクエリ/ CTEと条件付き集計を使用することです。

SELECT c.date, c.week_nb, c.id_congestion, c.id_element,
       ROW_NUMBER() OVER (PARTITION BY c.id_element ORDER BY c.date),
       (CASE WHEN seqnum = 1 THEN 1 ELSE 0 END) as week_count
FROM (SELECT c.*,
             ROW_NUMBER() OVER (PARTITION BY c.congestion.id_element, c.week_nb
                                ORDER BY c.date) as seqnum
      FROM congestion c
     ) c
WHERE c.date >= '2014.01.01' AND c.date <= '2014.12.31'
ORDER BY id_element, date
0
Gordon Linoff

分割されたセットを小さくして、カウントされたフィールドに重複がない点まで：

SELECT congestion.date, congestion.week_nb, congestion.id_congestion,
   congestion.id_element,
ROW_NUMBER() OVER(
    PARTITION BY congestion.id_element
    ORDER BY congestion.date),
COUNT(congestion.week_nb) -- remove distinct 
OVER(
    PARTITION BY congestion.id_element,
                 -- add new fields which will restart counter in case duplication
                 congestion.id_congestion
) AS week_count
FROM congestion
WHERE congestion.date >= '2014.01.01'
AND congestion.date <= '2014.12.31'
ORDER BY id_element, date
0
Agnius Vasiliauskas