是否有可能自我加入要求不同的日期？

Question

試圖尋找答案，閱讀這樣的帖子：SQL Self-join with data comparison for different days 但不能很好理解這將如何在這種情況下工作。

希望有任何幫助;

我有一個

• 用戶ID表（數字）

• 用戶類型（字符串，說明他們是否會員或客戶）

• sales_date（時間戳字段）

• （加上其他欄目，如他們購買的物品和我目前不感興趣的物品的價格）

我想寫一個查詢，它會告訴我每個月有多少人成爲會員和作爲訪客。 因此，我可以回答如下問題： 「9月有多少人在這裏，10月又回來了？」 「9月份會員人數有多少，但在10月降級爲客人？」 「9月有多少人是客人，但在10月升級爲會員？」

1：當需要從同一個表/相同查詢請求2個不同日期範圍時，自加入的方式是什麼？

2：我想我需要請求UserID，然後UserType for Sept和UserType for October。這聽起來正確嗎？不知道如何要求2個不同的日期

SELECT 
     t1.UserID, 
     t1.UserType as UserTypeSept, 
     t2.UserType as UserTypeOct 
    FROM 
     my_table t1 
     join my_table t2 
      on t1.UserID = t2.UserID 
      AND t2.day > '2015-01-01' AND t2.day < '2015-02-01' 
    where 
     t1.day >'2015-02-01' AND t1.day <'2015-03-01' 
; 

我在思考沿着正確的車道？ 即使這個工作，它不會告訴我有多少來自「成員」從九月至十月「客人」改變，但至少顯示出2個不同的列中的值

感謝

Answer 1

我會建議使用分析功能，而不是自我加入，這是更昂貴的。您的數據適合窗口數據。 請運行下面的查詢，然後調整到您的表。 您可能需要格式打印的時間段，並使用CASE子句進行後續月份之間的轉換，如「Member - Guest」到更有意義的名稱。

 WITH 
    members AS ( 
    SELECT 1 AS UserID, 'Member' AS UserType, TIMESTAMP '2015-01-01' AS sales_date 
    UNION ALL SELECT 1 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-02-01' AS sales_date 
    UNION ALL SELECT 2 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-01-01' AS sales_date 
    UNION ALL SELECT 2 AS UserID, 'Member' AS UserType,TIMESTAMP '2015-02-01' AS sales_date 
    UNION ALL SELECT 3 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-01-01' AS sales_date 
    UNION ALL SELECT 3 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-02-01' AS sales_date 
    UNION ALL SELECT 4 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-01-01' AS sales_date 
    UNION ALL SELECT 4 AS UserID, 'Member' AS UserType,TIMESTAMP '2015-02-01' AS sales_date 
    UNION ALL SELECT 5 AS UserID, 'Guest' AS UserType, TIMESTAMP '2016-07-01' AS sales_date 
    UNION ALL SELECT 5 AS UserID, 'Guest' AS UserType, TIMESTAMP '2016-08-01' AS sales_date 
    UNION ALL SELECT 6 AS UserID, 'Member' AS UserType,TIMESTAMP '2016-03-01' AS sales_date 
    UNION ALL SELECT 7 AS UserID, 'Guest' AS UserType, TIMESTAMP '2016-04-01' AS sales_date 
    UNION ALL SELECT 7 AS UserID, 'Guest' AS UserType, TIMESTAMP '2016-05-01' AS sales_date 
    UNION ALL SELECT 8 AS UserID, 'Guest' AS UserType, TIMESTAMP '2016-01-01' AS sales_date 
    UNION ALL SELECT 8 AS UserID, 'Member' AS UserType,TIMESTAMP '2016-02-01' AS sales_date 
    UNION ALL SELECT 9 AS UserID, 'Guest' AS UserType, TIMESTAMP '2016-01-03' AS sales_date 
    UNION ALL SELECT 9 AS UserID, 'Member' AS UserType,TIMESTAMP '2016-02-06' AS sales_date) 
SELECT 
    COUNT(*), 
    member, 
    period, 
    year 
FROM (
    SELECT 
    UserType, 
    UserID, 
    sales_date, 
    FORMAT_DATE("%Y",DATE(sales_date)) AS year, 
    CONCAT(
    FORMAT_DATE("%b",DATE(sales_date)), 
    ' - ', 
    FORMAT_DATE("%b", DATE(LEAD(sales_date,1) OVER (PARTITION BY userId ORDER BY sales_date ASC))) 
    ) AS period, 
    CONCAT(UserType,' - ', LEAD(UserType,1) OVER (PARTITION BY userId ORDER BY sales_date ASC)) AS member 
    FROM 
    members 
    ORDER BY 
    userid) 
WHERE 
    member IS NOT NULL 
    and year = '2016' 
GROUP BY 
year, 
    member, 
    period 

Answer 2

1：是自加入需要索要 從同一個表/同樣的查詢範圍是2個不同的日期時，要走的路？

不是真的！這取決於！在你的情況 - 參見下面的＃2

2：我想我要問的用戶ID，那麼用戶類型爲九月VS 用戶類型爲十月

我想下面做你的期望。
請注意：它會在每個月末查找UserType，並將其用作各個月份的用戶類型。

/* 
WITH my_table AS (
    SELECT 1 AS UserID, 'Member' AS UserType, TIMESTAMP '2015-09-01' AS sales_date UNION ALL 
    SELECT 1 AS UserID, 'Member' AS UserType, TIMESTAMP '2015-09-02' AS sales_date UNION ALL 
    SELECT 1 AS UserID, 'Member' AS UserType, TIMESTAMP '2015-09-03' AS sales_date UNION ALL 
    SELECT 1 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-09-10' AS sales_date UNION ALL 
    SELECT 1 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-10-01' AS sales_date UNION ALL 
    SELECT 1 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-10-02' AS sales_date UNION ALL 
    SELECT 2 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-09-01' AS sales_date UNION ALL 
    SELECT 2 AS UserID, 'Member' AS UserType, TIMESTAMP '2015-10-01' AS sales_date UNION ALL 
    SELECT 3 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-09-01' AS sales_date UNION ALL 
    SELECT 3 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-10-01' AS sales_date UNION ALL 
    SELECT 4 AS UserID, 'Guest' AS UserType, TIMESTAMP '2015-09-01' AS sales_date UNION ALL 
    SELECT 4 AS UserID, 'Member' AS UserType, TIMESTAMP '2015-10-01' AS sales_date) 
*/ 
SELECT 
    UserID, 
    MAX(CASE WHEN sales_year_month = '2015-09' THEN UserTypeAtEndOfMonth END) AS UserTypeSept, 
    MAX(CASE WHEN sales_year_month = '2015-10' THEN UserTypeAtEndOfMonth END) AS UserTypeOct 
FROM (
    SELECT 
    UserID, 
    FORMAT_DATE('%Y-%m', DATE(sales_date)) AS sales_year_month, 
    ARRAY_AGG(UserType ORDER BY sales_date DESC LIMIT 1)[OFFSET(0)] AS UserTypeAtEndOfMonth 
    FROM my_table 
    GROUP BY 1, 2 
) 
GROUP BY 1 

如果你想