MySQL Subquery Group By

Question

I have a query that displays a list of race results based on a person's id (athleteid). I have queried the database so that it lists the person's races in order of time (performance) and event (eventid) but I'm struggling to set this up as a subquery so that I can group the results afterwards to leave me with the fastest performance for each eventid. This is what I have so far:

$id = $_GET['id'];
$query = sprintf("SELECT events.eventcode, meetings.meetingid, meetings.meetingname, meetings.location, meetings.meetingdate, DATE_FORMAT(meetings.meetingdate,'%%d %%b %%Y') AS date, results.performance, results.unit, results.wind, agegroups.agegroup
FROM results 
JOIN athletes ON athletes.athleteid = results.athleteid
JOIN meetings ON meetings.meetingid = results.meetingid
JOIN events ON events.eventid = results.eventid
JOIN agegroups ON agegroups.agegroupid = results.agegroupid
WHERE results.athleteid='$id' AND events.eventtype = 'track' ORDER BY results.eventid asc, results.performance asc, meetings.meetingdate desc");

This works fine and displays all the relevant entries in the correct order. I then tried to turn it in to a subquery so that I could then use GROUP BY, but with no success. This is where I was trying to go with it:

$id = $_GET['id'];
$query = sprintf("SELECT * FROM (SELECT events.eventcode, meetings.meetingid, meetings.meetingname, meetings.location, meetings.meetingdate, DATE_FORMAT(meetings.meetingdate,'%%d %%b %%Y') AS date, results.performance, results.unit, results.wind, agegroups.agegroup
FROM results 
JOIN athletes ON athletes.athleteid = results.athleteid
JOIN meetings ON meetings.meetingid = results.meetingid
JOIN events ON events.eventid = results.eventid
JOIN agegroups ON agegroups.agegroupid = results.agegroupid
WHERE results.athleteid='$id' AND events.eventtype = 'track' ORDER BY results.eventid asc, results.performance asc, meetings.meetingdate desc) AS t1
GROUP BY t1.eventid");

However, this gives me an error which states: Unknown column 't1.eventid' in 'group statement'

Any help is greatly appreciated

Answer 1

You have not selected the eventid in you subquery. How can you then group by if it is not there?.

SELECT events.eventid,events.eventcode, 
meetings.meetingid, meetings.meetingname, 
meetings.location, meetings.meetingdate, 
DATE_FORMAT(meetings.meetingdate,'%%d %%b %%Y') AS date, 
results.performance, results.unit, results.wind, 
agegroups.agegroup
.......

Answer 2

that's cause you don't have that column on the sub-query, try adding the column on the sub-select:

$id = $_GET['id'];
$query = sprintf("SELECT * FROM (SELECT events.eventid, events.eventcode, meetings.meetingid, meetings.meetingname, meetings.location, meetings.meetingdate, DATE_FORMAT(meetings.meetingdate,'%%d %%b %%Y') AS date, results.performance, results.unit, results.wind, agegroups.agegroup
FROM results 
JOIN athletes ON athletes.athleteid = results.athleteid
JOIN meetings ON meetings.meetingid = results.meetingid
JOIN events ON events.eventid = results.eventid
JOIN agegroups ON agegroups.agegroupid = results.agegroupid
WHERE results.athleteid='$id' AND events.eventtype = 'track' ORDER BY results.eventid asc, results.performance asc, meetings.meetingdate desc) AS t1
GROUP BY t1.eventid");