Complex MySQL Query, Grouping By Invoice Number and Adding Multiple Values To Insert Into Database

Question

I have a table that looks like the above. I need to be able to update values in a database based on an ioID (the invoice number)
The value I need to add is the hours times the uSalary, however as you will notice above the hours can and well have been added on an ongoing basis. For example:
smarotti has added 4.5 (0.5 + 4.0) hours for the ioID 14190 (last 2 rows) for a total cost of $143.55
So what I need is to have the value $143.55 update the record 14190 (ioID) on a new column (userCost)
So:
the userID - ddevries did 1 hour worth of work at the rate of $23.20 that needs to be update on the record 8026
the userID - kmurtha did 20 (.5 + .25 + 6.5 + .25 + 6.5 + 6) hours worth of work $696 (20 * 34.80) that needs to be update on the record 9462
make sense? anyone have any thoughts on how to go about doing this?
Thanks
Vern

Answer 1

Okay
assuming you add the column to your table the query would look like the below:
UPDATE workers
                INNER JOIN (SELECT
                                                round(SUM(hours*uSalary),1) AS cost,
                                                ioID,
                                                userid
                                        FROM
                                                workers
                                        GROUP BY ioID, userid ) b
                ON workers.ioID = b.ioID
        SET workers.userCost=b.cost
WHERE workers.ioid = b.ioID
AND     workers.userID = b.userID
Or if you would just like to query the data:
SELECT  round(SUM(hours*uSalary),1) AS usercost,ioID,userid
FROM workers
GROUP BY ioID, userid