Question

我不得不设置一个查询来检索客户上的最后评论，如果没有人对他们进行评论超过4周。我可以使用下面的查询使其工作，但由于某种原因，注释列将不会显示最新的记录。相反，它显示最旧的，但日期显示最新。这可能只是因为我在SQL上是一个菜鸟，但究竟我在这里做错了什么？

SELECT DISTINCT
    customerid, id, customername, user, MAX(date) AS 'maxdate', comment
FROM comments
WHERE customerid IN 
   (SELECT DISTINCT id FROM customers WHERE pastdue='1' AND hubarea='1') 
AND customerid NOT IN 
   (SELECT DISTINCT customerid FROM comments WHERE DATEDIFF(NOW(), date) <= 27)
GROUP BY customerid
ORDER BY maxdate

第一个“WHERE”子句只是确保它只显示来自特定区域的客户，并确保它们“已过期”。第二个确保客户在过去27天内未被评论过。它按customerid分组，因为这是与每个客户关联的数字。当我得到结果时，一切都是正确的，除了评论栏......任何想法？

Answer 1

更好地加入嵌套查询，因此您使用连接而不是嵌套查询加入提高你的速度此查询可以解决您的问题。

SELECT DISTINCT customerid,id, customername, user, MAX(date) AS 'maxdate', comment FROM comments inner join customers on comments.customerid = customers.id WHERE comments.pastdue='1' AND comments.hubarea='1' AND DATEDIFF(NOW(), comments.date) <= 27 GROUP BY customerid ORDER BY maxdate

Answer 2

每个案例都需要有子查询。

SELECT  a.*
FROM    comments a
        INNER JOIN
        (
            SELECT customerID, max(`date`) maxDate
            FROM    comments
            GROUP BY customerID
        ) b ON a.customerID = b.customerID AND
                a.`date` = b.maxDate
        INNER JOIN
        (
            SELECT DISTINCT ID
            FROM customers
            WHERE pastdue = 1 AND hubarea = 1
        ) c ON c.ID = a.customerID
        LEFT JOIN
        (
            SELECT DISTINCT customerid 
            FROM comments 
            WHERE DATEDIFF(NOW(), date) <= 27
        ) d ON a.customerID = d.customerID
WHERE   d.customerID IS NULL

第一次加入获取每位客户的最新记录。
第二个联接仅显示来自特定区域的客户，并且它们“已过期”。
使用LEFT JOIN的第三个联接选择过去27天内未评论过的所有客户。在这种情况下，由于条件d.customerID IS NULL，仅选择不在列表中的记录。

但是要缩短查询时间，如果customers表已经有unique个客户记录，那么就不需要在其上有子查询。直接加入表并将条件放在WHERE条款。

SELECT  a.*
FROM    comments a
        INNER JOIN
        (
            SELECT customerID, max(`date`) maxDate
            FROM    comments
            GROUP BY customerID
        ) b ON a.customerID = b.customerID AND
                a.`date` = b.maxDate
        INNER JOIN customers c
            ON c.ID = a.customerID
        LEFT JOIN
        (
            SELECT DISTINCT customerid 
            FROM comments 
            WHERE DATEDIFF(NOW(), date) <= 27
        ) d ON a.customerID = d.customerID
WHERE   d.customerID IS NULL AND
        c.pastdue = 1 AND 
        c.hubarea = 1

Answer 3

试试这个

select  customerid, id, customername, user,date, comment from(
  select customerid, id, customername, user,date, comment, 
      @rank :=  IF(@current_customer = id, @rank+ 1, 1),
      @current_customer := id
    from comments
    where customerid IN 
      (SELECT DISTINCT id FROM customers WHERE pastdue='1' AND hubarea='1') 
      AND customerid NOT IN 
      (SELECT DISTINCT customerid FROM comments WHERE DATEDIFF(NOW(), date) <= 27)
    order by customerid, maxdate desc
) where rank <= 1

Answer 4

我认为这可能会做你想要实现的目标。如果你可以执行它并且可能会报告它是否有，我可以根据需要进行调整。逻辑上，它“应该”起作用 - 如果我正确地理解了你的问题：）

SELECT X.customerid, X.maxdate,  co.id, c.customername, co.user, co.comment
FROM 
    (SELECT customerid, MAX(date) AS 'maxdate'
    FROM comments cm
    INNER JOIN customers cu ON cu.id = cm.customerid
    WHERE cu.pastdue='1' 
    AND cu.hubarea='1' 
    AND DATEDIFF(NOW(), cm.date) <= 27)
    GROUP BY customerid) X
INNER JOIN comments co ON X.customerid = co.customerid and X.maxdate = co.date
INNER JOIN customer c  ON X.customerid = c.id
ORDER BY X.maxdate

Answer 5

您的两个表列不包含在聚合函数或GROUP BY子句中。例如，假设您有两个具有相同客户ID和相同日期的数据行，但具有不同的注释数据。 SQL应如何聚合这两行？ :(它会产生错误......

MySQL Query无法正确显示

5 个答案: