Question

I have a not-very-normalized MySQL table with the following values:

customer_ID | date | score | sale

As I am scoring the “purchase experience”, I would like to check the total sale value for each customer based on his last score. I do not mind about previous scores, just about last one.

Let’s say I have:

customer_ID | date      | score | sale  
a           | yesterday | 3     | 10  
a           | today     | 6     | 35  
b           | today     | 10    | 20  
c           | yesterday | 4     | 5  

The result for customers purchases with score > 5 should be:

num of customers | total sale values  
2                | 65

Any idea of how to create such query?

Edit:

What I want to know is how much has a customer spent in purchases in total, but just on customers whose last score was bigger than 5.

Answer 1

SELECT  COUNT(DISTINCT aa.customer_ID) `num of customers`,
        SUM(aa.sale) `total sale values `
FROM    table1 aa
        INNER JOIN
        (
            SELECT  a.customer_ID
            FROM    table1  a
                    INNER JOIN
                    (
                        SELECT  customer_ID, max(date) max_date
                        FROM    table1
                        GROUP   BY customer_ID
                    ) b ON a.customer_ID = b.customer_ID AND
                            a.date = b.max_date AND a.score > 5
        ) final ON aa.customer_ID = final.customer_ID

• SQLFiddle Demo

much more simplified,

SELECT  COUNT(DISTINCT c.customer_ID) `num of customers`,
        SUM(c.sale) `total sale values `
FROM    table1  a
        INNER JOIN
        (
            SELECT  customer_ID, max(date) max_date
            FROM    table1
            GROUP   BY customer_ID
        ) b ON a.customer_ID = b.customer_ID AND
                a.date = b.max_date AND a.score > 5
        INNER JOIN table1 c
            ON a.customer_ID = c.customer_ID

• SQLFiddle Demo