Trouble with MySQL query using AVG()

Question

I am using a query that takes an average of all the records for each given id...

$query = \"SELECT bline_id, AVG(flow) as flowavg 
          FROM blf 
                   


        

Answer 1

If these are really updated every day, then use date arithmetic:

SELECT bline_id, AVG(flow) as flowavg
FROM blf
WHERE bline_id BETWEEN 1 AND 30 and
      date >= date_sub(now(), interval 10 day)
GROUP BY bline_id
ORDER BY bline_id ASC

Otherwise, you have to put in a counter, which you can do with a correlated subquery:

SELECT bline_id, AVG(flow) as flowavg
FROM (select blf.*,
             (select COUNT(*) from blf blf2 where blf2.bline_id = blf.bline_id and blf2.date >= blf.date
             ) seqnum
      from blf
     ) blf
WHERE bline_id BETWEEN 1 AND 30 and
      seqnum <= 10
GROUP BY bline_id
ORDER BY bline_id ASC