mysql，php用多个用户标识每月计算平均值

Question

This is driving me crazy, I cant seam to manage this without massive amount of code, this is my sql table:

userid    date        orderValue
2       2012-01-01      2000
1       2012-01-01      3000
1       2012-01-01      5000
1       2012-01-02      5000
2       2012-01-02      8000
2       2012-01-02      8000

For each month I need to get the mean value per user from the first date ever intill the current month.

The output I'am looking for is something along the line of $orderArray[$month][$userid]['mean']

I don't relay need the code, jut need to get my mind out the current thoughts that man stuck on. How would you go about solving this?

Answer 1

Something along the lines of:

SELECT
  `userid`,
  DATE_FORMAT(`date`, '%Y%m') AS `month`,
  AVG(`orderValue`) AS `mean`
FROM
  `orderTable`
GROUP BY
  `userid`,
  `month`

Note that I'm using DATE_FORMAT instead of MONTH . If you don't do this, January 2012 and January 2013 would effectively be merged, which I guess is not what you want.

You'll have to create the desired result array yourself in PHP by iterating over the SQL result set and putting each mean value in the appropriate place.

Answer 2

Try this ::

    Select
    userid,
    SUM(ordervalue)/count(*) as mean

    from table 
    group by 

   userid