Update table based on conditions from another table,that include functions - mysql

Question

I have 2 mysql tables like in the example below:
CARS:
RaceID CarID Dis Grd Date Time
8 1 200 A 2010-10-10 20.50
8 2 300 A 2010-10-10 30.50
8 3 200 A 2010-10-10 20.10
9 1 200 A 2010-11-10 20.00
12 1 200 A 2011-12-11 19.50
RACES:
RaceId CarID Dis Grd Date Exp_Time
10 1 200 A 2011-11-11
10 2 200 A 2011-11-11
10 3 200 A 2011-11-11
I want to Add data on Races table at column Exp_Time based on data from CARS table.
For example:
RACES.Exp_Time=AVG(CARS.Time)
WHERE
CARS.CarID=RACES.CarID
CARS.Dis=RACES.Dis
CARS.Grd=RACES.Grd
CARS.Date<RACES.Date
The idea is that expected Time is AVG from previous races times on same distance and grd. Future races should be excluded from calculation AVG.
The problem is getting the date condition from RACES table.
I do this query:
UPDATE `RACES` c
INNER JOIN (
SELECT CARS.CarID, CARS.Dis, CARS.Grd, CARS.Date, AVG(Time) AS `Exp_Time`
FROM CARS
WHERE CARS.Date<'2011-11-11'
GROUP BY CarID, Dis, Grd
)
x ON c.CarID=x.CarID AND c.Dis=x.Dis AND c.Grd=x.Grd
SET c.Exp_Time=x.Exp_Time
And it works when I type myseld the date - 2011-11-11
I don't know how to get the data from RACES table.
Can somebody help?
Thanks in advance!
Ivan

Answer 1

UPDATE `RACES` c
INNER JOIN (
SELECT CARS.CarID, CARS.Dis, CARS.Grd, CARS.Date, AVG(Time) AS `Exp_Time`
FROM CARS
WHERE CARS.Date < (SELECT Date
FROM RACES
WHERE CARS.Date<RACES.Date
AND CARS.Grd=RACES.Grd
AND CARS.CarID=RACES.CarID
AND CARS.Dis=RACES.Dis
LIMIT 1
)
GROUP BY CarID, Dis, Grd
)
x ON c.CarID=x.CarID AND c.Dis=x.Dis AND c.Grd=x.Grd
SET c.Exp_Time=x.Exp_Time

Answer 2

2011-11-11 I don't know how to get the data from RACES table.
You can move this predicate to the JOIN condition like so:
UPDATE `RACES` c
INNER JOIN (
SELECT
CarID, Dis, Grd, Date, AVG(Time) AS `Exp_Time`
FROM CARS
GROUP BY CarID, Dis, Grd
)x ON c.CarID = x.CarID
AND c.Dis = x.Dis
AND c.Grd = x.Grd
AND x.DATE(`Date`) < c.DATE(`Date`)
SET c.Exp_Time = x.Exp_Time;