Question

我有一个订阅表，可以按日期跟踪会员续订。续订是针对日历年的，但会员最早可以在10月1日续订，在这种情况下，他们将在下一年的12月31日之前更新。因此可以在1月续订，然后在同年10月再次更新。我按月报告了会员总数，我希望避免将其计为2个会员资格。

由于上述续订选项，每条记录都有一个唯一的prodID，但可以有一个memberID的记录。 payDate是交易日期

我的陈述是：

$sql = "SELECT 
            EXTRACT(MONTH FROM payDate) as month, 
            EXTRACT(YEAR FROM payDate) as year, 
            count(*) 
            FROM 
                memberDues
            WHERE payDate >= $lastYear-10-01
            GROUP BY 
                month, 
                year
            ORDER BY 
                year ASC, 
                month ASC";

我得到这样的输出（未格式化）：

Member dues paid by month  
October         46  
November        30  
December        99  
January         42  
February         8  
March            9  
April            4  
May              1  
June             3  
Member Total:  242

如何修改select语句以避免在报告期内重复续订？

Answer 1

您需要按memberID进行分组才能让一个成员续订不被重复。

  SELECT year, month, count(memberID) FROM (
  SELECT memberID,
  EXTRACT(MONTH FROM payDate) as month, 
    EXTRACT(YEAR FROM payDate) as year, 
    count(*) 
    FROM 
        memberDues
    WHERE payDate >= $lastYear-10-01
    GROUP BY 
        memberID,
        month, 
        year
    ORDER BY 
        year ASC, 
        month ASC";
    )TMP GROUP BY year, month

Answer 2

为每个月计算不同的memberID应该完成这项工作：

                SELECT 
                EXTRACT(MONTH FROM payDate) as month, 
                EXTRACT(YEAR FROM payDate) as year, 
                count(DISTINCT memberID) 
                FROM 
                    memberDues
                WHERE payDate >= $lastYear-10-01
                GROUP BY 
                    month, 
                    year
                ORDER BY 
                    year ASC, 
                    month ASC

按成员ID计算最近的续订

2 个答案: