Select to Calculate Sales Average by Customer taking First Sales into Account MYSQL

问题

I have this Sales Table by Customer in Mysql

+-----------+------------+-------+-----------------+
| Customer  |    Date    | Sales | Date_First_Sale |
+-----------+------------+-------+-----------------+
| Jane      | 2016-04-30 |   903 | 2015-02-03      |
| Jane      | 2016-02-03 |    51 | 2015-02-03      |
| Jane      | 2016-03-09 |   192 | 2015-02-03      |
| John      | 2016-05-10 |    64 | 2015-10-03      |
| John      | 2016-04-16 |   880 | 2015-10-03      |
| John      | 2016-08-17 |   386 | 2015-10-03      |
| John      | 2016-03-01 |   503 | 2015-10-03      |
| Juan      | 2016-07-06 |   765 | 2015-09-01      |
| Juan      | 2016-01-20 |    36 | 2015-09-01      |
| Juan      | 2016-03-03 |   928 | 2015-09-01      |
| Momo      | 2016-06-29 |   573 | 2015-09-01      |
| Momo      | 2016-04-25 |   375 | 2015-09-01      |
| Momo      | 2016-06-10 |   999 | 2015-09-01      |
| Nour      | 2016-02-28 |   956 | 2015-05-01      |
| Nour      | 2016-01-03 |   582 | 2015-05-01      |
| Nour      | 2016-08-17 |   366 | 2015-05-01      |
| Philip    | 2016-03-22 |   296 | 2015-09-01      |
| Philip    | 2016-04-14 |   459 | 2015-09-01      |
| Sylvie    | 2016-03-29 |   551 | 2015-09-03      |
| Sylvie    | 2016-02-14 |   896 | 2015-09-03      |
+-----------+------------+-------+-----------------+

I need to calculate the Average Sales by Customer calculated on a WEEKLY basis in the last 12 months (52 or 53 weeks depending on the calendar?), starting from Today.

Now the problem is that I do not want to calculate the Average Weekly sales by customer for customers that have made their first purchase in a range below 12 months, for instance If current date is 2016-09-01, and Customers made his first purchase on 2016-07-24, the average should not be calculated on a 12 months basis but on the weekly sales generated between the 2016-07-24 and the 2016-09-01 only.

For customers who have made their First purchase before the 12 months range, then the average should be calculated on 12 months only.

I have been trying to find this SELECT but have not reached anything due to my limited Mysql knowledge for more complex queries!

Thanks in advance for your help

回答1:

This should help you

SELECT Customer, (total_sales/weeks) AS avg_sales FROM
(
SELECT Customer, total_sales, Date_First_Sale, IF(weeks>52,52,weeks) as weeks
FROM (
    SELECT Customer, SUM(Sales) AS total_sales, Date_First_Sale, TIMESTAMPDIFF(WEEK, Date_First_Sale, CURDATE()) AS weeks
    FROM (
        SELECT Customer, sales , Date_First_Sale
        FROM test.SO_customer
        WHERE Date > DATE_SUB(curdate(), INTERVAL 1 YEAR)
         ) as subTable
    GROUP BY Customer
    ) as subTable2
) as subTable3

来源：https://stackoverflow.com/questions/39326820/select-to-calculate-sales-average-by-customer-taking-first-sales-into-account-my

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mysql

average