group tick data to minute data using MySQL
What you want is something like this which uses the extract(HOUR_MINUTE..)

SELECT t1.date, t1.time, t2.price, t2.vol
FROM (
  SELECT date,
    extract(HOUR_MINUTE from time) AS time,
    max(id) AS maxid
  FROM tbl
  GROUP BY date, extract(HOUR_MINUTE from time)
) AS t1
JOIN tbl AS t2
  ON t1.maxid = t2.id;


The inner selects and groups by the date,hour/min, and grabs the max(id) and count(*). The outer joins back to the table and resolves to find the price.

In other news, why are you storing date and time separately? You should be using a timestamp.