如何在 mysql 中使用 group by 的子查询？

Question

I have one table with multiple rows for particular users.i am having data with many years like 2019,2018,2016 and more. i have two scenarios:

1.i want data of particular INVOICE_YEAR.

2,but same time i want FIRST DATE OF INVOICE GENERATED FOR PARTICULAR USER.

我的sql查询：

$yearOf 这是动态年份输入变量。

$yearOf = 2019;

$Records = "SELECT MIN(inv.INVOICE_DATE) AS MIN_INVOICE_DATE
                    FROM invoices as inv
                    LEFT JOIN customers as cm ON cm.CUSTOMER_ID = inv.CUSTOMER_ID 
                    where inv.INVOICE_YEAR IN (".$yearOf.")
                    group by inv.CUSTOMER_ID ORDER BY cm.CUSTOMER_NAME ASC";

如果我想要 INVOICE_YEAR IN ('2019') 的所有用户的数据，你可以看到我的查询。我的第一个条件将得到满足，我将获得 INVOICE_YEAR = 的所有用户数据2019.

但同时我想要第一个发票日期所以为此我使用了 MIN(inv.INVOICE_DATE) 但正如我使用的那样
where inv.INVOICE_YEAR IN (".$yearOf.") 这在 where 条件下所以它给了我特定年份的第一个发票日期。

但我希望所有用户的第一个发票日期为整个table。

我尝试使用子查询，但它显示 子查询 returns 超过 1 行的错误

我的子查询查询：

$Records = "SELECT 
                    (
                    SELECT MIN(inv.INVOICE_DATE) AS MIN_INVOICE_DATE FROM invoices AS inv GROUP BY inv.CUSTOMER_ID) AS MIN_INVOICE_DATE
                    FROM invoices as inv 
                    LEFT JOIN customers as cm ON cm.CUSTOMER_ID = inv.CUSTOMER_ID 
                    where inv.INVOICE_YEAR IN (".$yearOf.")
                    group by inv.CUSTOMER_ID ORDER BY cm.CUSTOMER_NAME ASC";

例如：

有 3 位顾客 101,102,103

table 中的数据如下：

id | customer_id | invoice_date | invoice_year
1  | 101         | 2019-01-01   |  2019
2  | 101         | 2016-01-01   |  2016
3  | 101         | 2017-01-01   |  2017
4  | 101         | 2016-01-02   |  2016
5  | 102         | 2019-01-02   |  2019
6  | 103         | 2018-01-02   |  2018
7  | 103         | 2019-01-07   |  2019
8  | 102         | 2015-01-02   |  2015

当我请求查询以获取 INVOICE_YEAR 2019 年的数据以及特定用户的第一个发票日期时，它应该给出如下输出：

id | customer_id | invoice_date | invoice_year | min_invoice_date
1  | 101         | 2019-01-01   |  2019        | 2016-01-01
5  | 102         | 2019-01-02   |  2019        | 2015-01-02
7  | 103         | 2019-01-07   |  2019        | 2019-01-07

如我所愿所有用户的MIN_INVOICE_DATE列中的第一个发票日期。

但它显示的数据如下：

id | customer_id | invoice_date | invoice_year | min_invoice_date
1  | 101         | 2019-01-01   |  2019        | 2019-01-01
5  | 102         | 2019-01-02   |  2019        | 2019-01-02
7  | 103         | 2019-01-07   |  2019        | 2019-01-07

Answer 1

您想提取每个客户在 2019 年的最早发票，以及整个 table 中最早发票的日期。

在 MySQL 8.0 中，您可以使用 window 函数解决此问题：

SELECT id, customer_id, invoice_date, invoice_year, min_invoice_date
FROM (
    SELECT 
        t.*,
        ROW_NUMBER() OVER(PARTITION BY customer_id, invoice_year ORDER BY invoice_date) rn,
        MIN(invoice_date) OVER(PARTITION BY customer_id) min_invoice_date
    FROM mytable t
) x
WHERE invoice_year = 2019 AND rn = 1

在早期版本中，您可以：

JOIN table 的查询计算每个客户的总体最小值 invoice_date
使用具有 NOT EXISTS 条件的相关子查询来筛选 2019 年最早的发票面额客户

查询：

SELECT t.id, t.customer_id, t.invoice_date, t.invoice_year, m.min_invoice_date
FROM mytable t
INNER JOIN (
    SELECT customer_id, MIN(invoice_date) min_invoice_date 
    FROM mytable 
    GROUP BY customer_id
) m ON m.customer_id = t.customer_id
WHERE 
    t.invoice_year = 2019
    AND NOT EXISTS (
        SELECT 1 
        FROM mytable t1
        WHERE t1.invoice_year = 2019 
        AND t1.customer_id = t.customer_id
        AND t1.invoice_date < t.invoice_date
    )

在这个demo on DB Fiddle中，两个查询return:

| id  | customer_id | invoice_date | invoice_year | min_invoice_date |
| --- | ----------- | ------------ | ------------ | ---------------- |
| 1   | 101         | 2019-01-01   | 2019         | 2016-01-01       |
| 5   | 102         | 2019-01-02   | 2019         | 2015-01-02       |
| 7   | 103         | 2019-01-07   | 2019         | 2018-01-02       |

Answer 2

我猜测您希望查看每个日历年每个客户的第一张（最早日期的）发票的详细信息。您希望该结果过滤为仅涵盖一年。

因此，从子查询开始查找每个日历年每个客户的第一张发票的日期。 (https://www.db-fiddle.com/f/bmBZ14Vr9Re6ahpfs2FF2X/0)

      SELECT MIN(invoice_date) first_invoice_date,
             YEAR(invoice_date) calendar_year,
             customer_id
        FROM invoices
       GROUP BY YEAR(invoice_date), customer_id

然后通过将该子查询连接到您的原始 invoices table 来检索这些发票的详细信息。 (https://www.db-fiddle.com/f/bmBZ14Vr9Re6ahpfs2FF2X/1)

SELECT invoices.*
  FROM invoices
  JOIN (
          SELECT MIN(invoice_date) first_invoice_date,
                 YEAR(invoice_date) calendar_year,
                 customer_id
            FROM invoices
           GROUP BY YEAR(invoice_date), customer_id
       ) firsts 
           ON invoices.customer_id = firsts.customer_id
          AND invoices.invoice_date = firsts.first_invoice_date
  ORDER BY invoices.customer_id, 
           invoices.invoice_year, 
           invoices.invoice_date

然后，输入 WHERE invoices.invoice_year = 2019 以获得您想要的年份。

请注意，您的 invoice_year 列是不必要的，因为它始终可以从 YEAR(invoice_date) 计算得出。你应该考虑摆脱它。

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