在子查询中获取Id

  • Z时代
  • 2024-01-10
  • 分类：问答

我一直在APEX的拍卖网站上工作。对于拍卖网站，我需要做一个概述，说明哪些产品是由某人购买的。肯定它的只是我忘了，但我怎样才能获得结果在以下情况：在子查询中获取Id

3表

Table User 
USER_ID 
EMAIL 
Table Product 
PRODUCT_ID 
USER_ID 
Table Bid 
BID_ID 
PRODUCT_ID 
USER_ID 
CREDITS

Ofcourse有更多的列，但我想，让他们出来，使explenation稍微容易。

最少报名结果

显示产品从产品表。但只有当前用户的出价最高（Credits）。

到目前为止

我一直在想/想在这一个了很多，但在子查询结束不断收到死亡。 （：APP_USER）

SELECT * 
FROM "PRODUCT" 
WHERE "PRODUCT_ID" IN (SELECT "PRODUCT_ID" FROM "BID" 
         WHERE "USER_ID" = 
         (SELECT "USER_ID" FROM "USER" 
         WHERE lower("EMAIL") = lower(:APP_USER))) 
    and "PRODUCT_ID" = (SELECT "PRODUCT_ID" FROM "BID" 
         WHERE "CREDITS" = 
        (SELECT MAX("CREDITS") FROM "BID" 
         WHERE "PRODUCT_ID" = ?

*的Apex从当前用户返回的emailadress

真正的问题在“和”为用户过滤工作正常启动。我不知道如何在子查询中获取比较（当前）的PRODUCT_ID。我很确定，如果我在子查询的末尾得到这个值，它就可以工作。

使用Oracle数据库。

任何帮助表示赞赏:)

回答：

尝试用这个..

SELECT * 
FROM PRODUCT p 
WHERE p.PRODUCT_ID IN (SELECT PRODUCT_ID FROM BID" 
         WHERE "USER_ID" = 
         (SELECT "USER_ID" FROM "USER" 
         WHERE lower("EMAIL") = lower(:APP_USER))) 
    and "PRODUCT_ID" = (SELECT "PRODUCT_ID" FROM "BID" b 
         WHERE "CREDITS" = 
        (SELECT MAX("CREDITS") FROM "BID" 
         WHERE b.PRODUCT_ID" = p.product_id));

或

and "PRODUCT_ID" in (SELECT "PRODUCT_ID" FROM "BID" b 
         WHERE "CREDITS" = 
        (SELECT MAX("CREDITS") FROM "BID" 
         WHERE b.PRODUCT_ID" = p.product_id))

回答：

像这样的事情？

，你可能有问题，如果对投标的学分不是每个产品唯一的（但应该是在你的拍卖业务规则反正） 

SELECT 
    p.* 
FROM 
    Bid b 
    JOIN 
    -- get the max bid per product 
    (SELECT 
     PRODUCT_ID, MAX(CREDITS) AS MAX_C 
    FROM 
     Bid 
    GROUP BY 
     PRODUCT_ID) m ON b.PRODUCT_ID = m.PRODUCT_ID AND b.CREDITS = m.CREDITS 
    JOIN USER u ON b.USER_ID = u.USER_ID 
    JOIN Product p ON b.PRODUCT_ID = p.PRODUCT_ID 
WHERE 
    lower(u.EMAIL) = lower(:APP_USER)));

注意。

编辑

从查询长度的角度来看，以下为确保您只检查该用户实际已经过投标的产品胜，而不是其上方检查可能会更好所有产品。

SELECT 
    p.* 
FROM 
    Bid b 
    JOIN 
    -- get the max bid per product that the user bid on 
    (SELECT 
     PRODUCT_ID, MAX(CREDITS) AS MAX_C 
    FROM 
     Bid b2 
     JOIN (
      -- get only the products that the user has bid on 
      SELECT 
       DISTINCT b1.PRODUCT_ID 
      FROM 
       Bid b1 
       JOIN User u1 ON b1.USER_ID = u1.USER_ID 
      WHERE 
       lower(u1.EMAIL) = lower(:APP_USER))) dp 
     ON b2.PRODUCT_ID = dp.PRODUCT_ID 
    GROUP BY 
     PRODUCT_ID) m ON b.PRODUCT_ID = m.PRODUCT_ID AND b.CREDITS = m.CREDITS 
    JOIN USER u ON b.USER_ID = u.USER_ID 
    JOIN Product p ON b.PRODUCT_ID = p.PRODUCT_ID 
WHERE 
    lower(u.EMAIL) = lower(:APP_USER)));

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