Question

我一直在使用CTE（常用表格表达式）来编写将用于“更大图片”的小型查询。查询。

例如，我将创建一个CTE来计算一列计数。

然后基本上用另一个CTE创建该列的副本。

然后将它们连接在一起，这样我就可以为30天的窗口创建一个滚动总和。

一切似乎都在起作用，我最终得到的表格中有多行具有相同的值，因此总计数（总和）不正确。

这是使用CTE时常见的情况还是我做错了什么来创建重复的行？

我们说我有＆＃39; table1＆＃39;：

row_number | session_date | user_id | item
1           2017-01-01      alex      apple
2           2017-01-02      alex      orange

目标是拥有用户购买的项目的滚动总和。

WITH TEMP
AS (
    SELECT a.row_number
        ,a.session_date
        ,a.user_id
        ,a.item
        ,CASE 
            WHEN a.item = 'apple'
                THEN 1
            ELSE 0
            END AS item_apple
        ,CASE 
            WHEN a.item = 'orange'
                THEN 1
            ELSE 0
            END AS item_orange
    FROM table1 AS a
    )
    ,duplicate
AS (
    SELECT *
    FROM TEMP
    )
    ,new_table
AS (
    SELECT l.row_number
        ,r.session_date
        ,r.user_id
        ,r.item
        ,sum(r.item_apple) OVER (
            PARTITION BY r.session_date
            ,r.user_id
            ) AS sum_apple_30day
        ,sum(r.item_orange) OVER (
            PARTITION BY r.session_date
            ,r.user_id
            ) AS sum_orange_30day
    FROM TEMP AS l
    LEFT JOIN TEMP AS r ON (l.row_number = r.row_number)
    LEFT JOIN duplicate dp ON l.user_id = dp.user_id
        AND l.session_date <= dp.session_date
        AND l.session_date + interval '30 days' > dp.session_date
    )
SELECT *
FROM new_table

SQL小提琴：http://sqlfiddle.com/#!17/dade8/2/0

PostgreSQL 9.6

任何帮助将不胜感激！谢谢！

Answer 1

您可以尝试以下内容。

WITH temp  AS
(
SELECT
 user_id, item, MIN(session_date) AS FirstDate
FROM table1
GROUP BY user_id, item
),
DateVals AS
(

  SELECT
   t.*,   
 (CAST (DATE_PART('day', t.session_date ::timestamp -  md.FirstDate ::timestamp)  AS INTEGER)) / 30 AS windowValue
  FROM table1  AS t INNER JOIN temp AS md ON 
  t.user_id = md.user_id AND  t.item = md.item
 )
SELECT 
 dv.row_number, dv.user_id, dv.item,dv.session_date,
  ac.AppleCount , oc.OrangeCount
 FROM DateVals AS dv
 LEFT OUTER JOIN
 (
       SELECT
           row_number,                  

            ROW_NUMBER() OVER(PARTITION BY user_id,item,windowValue  ORDER BY session_date) AS AppleCount
       FROM DateVals
      WHERE item = 'apple'
   )AS ac ON dv.row_number = ac.row_number

   LEFT OUTER JOIN
 (
       SELECT
           row_number,       

            ROW_NUMBER() OVER(PARTITION BY user_id,item,windowValue  ORDER BY session_date) AS OrangeCount
       FROM DateVals
      WHERE item = 'orange'
   )AS oc ON dv.row_number = oc.row_number
ORDER BY dv.user_id, dv.item,dv.session_date

CTE是否在PostgreSQL中生成行重复？

1 个答案: