SQL Query - Grouping Data - sql

Question

So every morning at work we have a stand-up meeting. We throw the nearest object to hand around the room as a method of deciding who speaks in what order. Being slightly odd I decided it could be fun to get some data on these throws. So, every morning I memorise the order of throws (as well as other relevant things like who dropped the ball/strange sponge object that was probably once a ball too and who threw to someone who'd already been or just gave an atrocious throw), and record this data in a table:
+---------+-----+------------+----------+---------+----------+--------+--------------+
| throwid | day | date | thrownum | thrower | receiver | caught | correctthrow |
+---------+-----+------------+----------+---------+----------+--------+--------------+
| 1 | 1 | 10/01/2012 | 1 | dan | steve | 1 | 1 |
| 2 | 1 | 10/01/2012 | 2 | steve | alice | 1 | 1 |
| 3 | 1 | 10/01/2012 | 3 | alice | matt | 1 | 1 |
| 4 | 1 | 10/01/2012 | 4 | matt | justin | 1 | 1 |
| 5 | 1 | 10/01/2012 | 5 | justin | arif | 1 | 1 |
| 6 | 1 | 10/01/2012 | 6 | arif | pete | 1 | 1 |
| 7 | 1 | 10/01/2012 | 7 | pete | greg | 0 | 1 |
| 8 | 1 | 10/01/2012 | 8 | greg | alan | 1 | 1 |
| 9 | 1 | 10/01/2012 | 9 | alan | david | 1 | 1 |
| 10 | 1 | 10/01/2012 | 10 | david | dan | 1 | 1 |
| 11 | 2 | 11/01/2012 | 1 | dan | david | 1 | 1 |
| 12 | 2 | 11/01/2012 | 2 | david | alice | 1 | 1 |
| 13 | 2 | 11/01/2012 | 3 | alice | steve | 1 | 1 |
| 14 | 2 | 11/01/2012 | 4 | steve | arif | 1 | 1 |
| 15 | 2 | 11/01/2012 | 5 | arif | pete | 0 | 1 |
| 16 | 2 | 11/01/2012 | 6 | pete | justin | 1 | 1 |
| 17 | 2 | 11/01/2012 | 7 | justin | alan | 1 | 1 |
| 18 | 2 | 11/01/2012 | 8 | alan | dan | 1 | 1 |
| 19 | 2 | 11/01/2012 | 9 | dan | greg | 1 | 1 |
+---------+-----+------------+----------+---------+----------+--------+--------------+
I've now got quite a few days worth of data for this, and I'm starting to run some queries on it for my own purposes (I've not told the rest of the team yet...wouldn't like to influence the results). I've done a few with no issues, but I'm stuck trying to get a certain result out.
What I'm looking for is the number of times each person has been the last team member to receive the ball. Now, as you can see on the table, due to absences etc the number of throws per day is not always constant, so I can't simply select the receiver by thrownum.
In the case for the data above, it would return:
+--------+-------------------+
| person | LastReceiverTotal |
+--------+-------------------+
| dan | 1 |
| greg | 1 |
+--------+-------------------+
I've got this far:
SELECT MAX(thrownum) AS LastThrowNum, day FROM Throws GROUP BY day
Now, this returns some useful data. I get the highest thrownum for each and every day. It would seem like all I need to do is get the receiver for this value, and then get a count grouped by receiver to get my answer. This doesn't work, though, because the resultset isn't what it seems due to the above query using aggregate functions.
I suspect there's a much better way of designing tables to store the data to be honest, but equally I'm also sure there's a way to get this information with the tables as they are - some kind of inner query? I can't figure out how it would work. Can anyone shed some light on how this would be done?

Answer 1

The query that you have gives you the biggest thrownum for each day.
With that, you just do a inner join with your table and get the receiver and the number of times he happears.
select t.receiver as person, count(t.day) as LastReceiverTotal from Throws t
inner join (SELECT MAX(thrownum) AS LastThrowNum, day FROM Throws GROUP BY day) a on a.LastThrowNum = t.thrownum and a.day = t.day
group by t.receiver