Question

这是我桌子的样本。（实际表包含更多行）

--------------------------------------------------
fInvoice | fDebtorcode | fCompanyname | fdate
123      | A001        | ABC Company  | 2017-02-01
234      | A002        | CDE Company  | 2017-03-02
345      | A003        | FGH Company  | 2017-03-05
456      | A001        | ABC Company  | 2017-04-02
567      | A001        | ABC Company  | 2017-04-04
678      | A002        | CDE Company  | 2017-04-04

我想了解每月有多少公司从我们这里购买。这是我到目前为止所拥有的：

select 
fdebtorcode As Debtorcode, 
fcompanyname As CompanyName, 
(SELECT COUNT(*) FROM  invoicetable WHERE fdate > '2017-03-31' and fdate < '2017-05-01' and fdebtorcode = Debtorcode) As April,
(SELECT COUNT(*) FROM  invoicetable WHERE fdate > '2017-02-28' and fdate < '2017-04-01' and fdebtorcode = Debtorcode) As March,
(SELECT COUNT(*) FROM  invoicetable WHERE fdate > '2017-01-31' and fdate < '2017-03-01' and fdebtorcode = Debtorcode) As February
from tinvoicehistory 
where fdivision = 'Stationary'
group by fdebtorcode 
order by fdebtorcode

现在，我还有2个要求：

一个名为＆＃34;每月购买的专栏＆＃34;这给了我一个＆＃34;是＆＃34;对于每月购买的公司，或者没有＆＃34; no＆＃34;如果没有。
仅显示在这3个月内至少购买过一次的公司。（我目前的结果显示所有这些，包括已经关闭的那些）

请告诉我是否有更好的方法。所有帮助赞赏。感谢

Answer 1

考虑以下解决方案。我包装您的原始查询，略微修改，然后使用每月总计创建您想要的两列。如果公司在三个月内购买，则会在每月购买列中显示yes。如果公司至少在一个月内进行了购买，那么它会在任何购买列中显示yes。

我还删除了子查询，并使用条件聚合将它们替换为CASE个表达式。此外，我使用MONTH()函数而不是像您原来那样检查日期范围，这是笨拙的，甚至有点容易出错。它可能容易出错，因为它很容易破坏一个月的终点，而且二月并不总是每年有28个（闰年可能有29个）。

SELECT t.*,
       CASE WHEN t.February > 0 AND t.March > 0 AND t.April > 0
            THEN 'yes' ELSE 'no' END AS purchased_monthly,
       CASE WHEN t.February > 0 OR t.March > 0 OR t.April > 0
            THEN 'yes' ELSE 'no' END AS purchased_once
FROM
(
    SELECT
        fdebtorcode AS Debtorcode, 
        fcompanyname AS CompanyName,   -- non aggregate column; this may be bad
        SUM(CASE WHEN MONTH(fdate) = 2 THEN 1 ELSE 0 END) AS February,
        SUM(CASE WHEN MONTH(fdate) = 3 THEN 1 ELSE 0 END) AS March,
        SUM(CASE WHEN MONTH(fdate) = 4 THEN 1 ELSE 0 END) AS April
    FROM tinvoicehistory 
    WHERE fdivision = 'Stationary'
    GROUP BY fdebtorcode 
) t
ORDER BY t.fdebtorcode

Answer 2

您可以查看mysql的MONTH（）和YEAR（）函数。然后你可以尝试类似的东西：

SELECT fdebtorcode As Debtorcode, fcompanyname As CompanyName,COUNT(*) AS purchases
FROM tinvoicehistory 
WHERE fdivision = 'Stationary'
GROUP BY YEAR(fdate), MONTH(fdate) DESC, fdebtorcode 
ORDER BY fdebtorcode

开头。

Mysql检查客户是否每月购买

2 个答案: