具有内部选择的MYSQL SUM返回最大日期

Question

I am trying to come up with a single query which will take the following table (named sales ):

user_id  |  order_total   |   order_date  |
    1    |      100       |  2012-01-01   |
    1    |      200       |  2013-06-04   |
    1    |      150       |  2012-01-08   |
    2    |      100       |  2015-02-01   |
    3    |      105       |  2014-10-27   |

And will return the following:

user_id  |  order_total   |   num_orders  |  last_order  |
    1    |      450       |     3         | 2013-06-04   |
    3    |      105       |     1         | 2014-10-27   |
    2    |      100       |     1         | 2015-02-01   |

So far I have come up with the following SQL to get the result:

SELECT 
DISTINCT a.user_id,
SUM(order_total) AS order_total,
COUNT(*) AS num_orders,
b.order_date as last_order
FROM 
    `sales` AS a,
     (
        SELECT 
        order_date, 
        user_id
        FROM `sales` 
        ORDER BY order_date DESC
      ) AS b
WHERE a.user_id = b.user_id
GROUP BY user_id
ORDER BY order_total DESC

The problem, however is that it returns:

user_id  |  order_total   |   num_orders  |  last_order  |
    1    |      1350      |     9         | 2013-06-04   |
    3    |      105       |     1         | 2014-10-27   |
    2    |      100       |     1         | 2015-02-01   |

Is there some way to prevent the sub-query from affecting the results of Sum and Count? Or am I going about this the wrong way?

Answer 1

why are you using a subselect?

SELECT user_id, 
SUM(order_total) AS order_total, 
MAX(order_date) AS lastOrder, 
COUNT(*) AS num_orders 
FROM table 
GROUP BY user_id
ORDER BY order_total DESC