Question

所以我在我的代码中有这个查询：

        SELECT month, total_orders, first_orders, first_orders::numeric / total_orders::numeric * 100 AS ratio
        FROM (
          SELECT month, COUNT(1) AS total_orders
          FROM (
            SELECT DISTINCT date_trunc('month', date) AS month, email
            FROM shop_orders
            WHERE status_code = 'CONFIRMED'
          ) AS customers
          GROUP BY month
        ) AS total_orders_my_month

        LEFT JOIN (
          SELECT month, COUNT(1) AS first_orders FROM (
            SELECT email, date_trunc('month', MIN(date)) AS month
            FROM shop_orders
            WHERE status_code = 'CONFIRMED'
            GROUP BY email
          ) AS first_orders_by_month
          GROUP BY month
        ) AS first_orders_by_month2 USING (month)

        ORDER BY month DESC

它的作用是以一种形式重新调整行：month |那个月的客户数量这个月的第一次客户数量首次购客的百分比

我需要的是每个月还能找到超过1个订单的客户数量。

所以我添加了这段代码：

        LEFT JOIN (
          SELECT month, COUNT(1) AS multiple_orders FROM (
            SELECT email, date_trunc('month', MIN(date)) AS month
            FROM shop_orders
            WHERE status_code = 'CONFIRMED'
            GROUP BY email HAVING COUNT(1) >=2
          ) AS multiple_orders_by_month
          GROUP BY month
        ) AS multiple_orders_by_month2 USING (month)

然而，这仅返回首次订购客户而非所有客户的2个或更多订单的客户。有人可以帮忙吗？

注意：所有数据都在shop_orders表中，唯一客户由电子邮件字段标识，日期字段包含有关订单日期的信息。

我希望它清楚。

我对postgresql很新，所以有人指向正确的方向吗？感谢。

Answer 1

我首先想指出的是，我是从纯SQL路线而不是postsgresql看这个，但理论基本相同。您的子查询SQL可能过于复杂，这是我正在研究如何创建查询：

首先，获取所有电子邮件地址的列表以及每月订购的订单数量;以下查询将返回分配给每封电子邮件的订单数量：

SELECT
    month
    , email
    , COUNT(*)
FROM
    shop_orders
WHERE
    status_code = 'Confirmed'
GROUP BY
    month
    , email

这将每个月返回每个电子邮件地址的订单计数。然后，您可以使用HAVING过滤器方法将此列表限制为每月包含多个电子邮件的所有电子邮件。

SELECT
    month
    , email
    , COUNT(*) as ordersThisMonth
FROM
    shop_orders
WHERE
    status_code = 'Confirmed'
GROUP BY
    month
    , email
HAVING
    COUNT(*) > 1

然后可以使用另一个聚合来访问此子查询，例如SUM(CASE WHEN ordersThisMonth > 1 THEN 1 ELSE 0 END)，只有在收到多个订单时才会计算。我个人会尝试将您的查询简化为两个子查询，一个包含特定于month的详细信息，另一个包含month和email的详细信息。

（以下代码未经语法检查，如前所述，我从纯粹的SQL角度来看这个。）

SELECT 
    month
    , total_orders
    , first_orders
    /* Add together all firstMonthCount entries as it should only be 1 for the customers first month */
    , SUM(firstMonthCount)::numeric / total_orders::numeric * 100 AS ratio
    /* Count only e-mails which have more than one order for the month */
    , SUM(CASE WHEN orderCount > 1 THEN 1 ELSE 0 END) AS multipleOrders
FROM 
    /*The following sub-query gets all the aggregates specific to a month */
    (   SELECT 
            date_trunc('month', date) AS month
            , COUNT(1) AS total_orders
        FROM 
            shop_orders
        WHERE 
            status_code = 'CONFIRMED'
        GROUP BY 
            month
    ) AS month_attributes
    /*The following sub-query gets all the aggregates specific to a month AND e-mail */
    LEFT JOIN (
        SELECT
            date_trunc('month', date) AS month
            , email
            , CASE WHEN date_trunc('month', date) = date_trunc('month', MIN(date)) THEN 1 ELSE 0 END AS firstMonthCount
            , COUNT(*) AS orderCount 
        FROM 
            shop_orders
        WHERE 
            status_code = 'CONFIRMED'
        GROUP BY 
            month
            ,email
    ) AS email_month_attributes USING (month)
GROUP BY 
    month

希望上述有关HAVING的查询和说明可以帮助您找到适合您目的的解决方案。我确信如果需要可读性/性能，可以进一步简化上述查询。

Postgresql查询返回一个月内发出超过1个订单的客户数量

1 个答案: