How do you SUM values based on a MIN date? - mysql

Question

Working on an exercise for school trying to calculate the number of points scored by a basketball player ONLY during their first game.
So if I have a table that reports lots of games (Separate rows for 1st and 2nd half) that looks like this:
Game Date Player Half Points
1990-01-01 Mike 1 10
1990-01-01 Mike 2 10
1990-01-03 Mike 1 5
1990-01-03 Ben 2 8
1990-01-05 Kelly 1 4
1990-01-05 Kelly 2 4
1990-01-07 Kelly 1 10
And I want it to end up like this:
Game Date Player Points
1990-01-01 Mike 20
1990-01-03 Ben 8
1990-01-05 Kelly 8
How would I do this?
I have been trying to use the code:
SELECT min(game_Date), player, sum(points);
But it keeps counting points for ALL games, not just points scored during the 1st game, of which there can be one record for the first half and one record for the second.

Answer 1

First you need to find the players' first games, like this
select player, min(game_date) as firstGameDate
from yourtable
group by player
and then get the points in that game by joining to the table again
select yourtable.player, firstgame.firstGameDate, sum(points) as firstGamePoints
from yourtable
inner join
(
select player, min(game_date) as firstGameDate
from yourtable
group by player
) firstgame
on yourtable.player = firstgame.player
and yourtable.game_date = firstgame.firstgameDate
group by yourtable.player, firstgame.firstgameDate
Some varieties of SQL allow you to use ranking functions which could eliminate the need to join to the table itself, but this will work in all varieties.

Answer 2

You have to use your logic. First you have to only grab the first game for each player (inner query). Then from there, you count the points
SELECT t.game_date, t.player, SUM(t.points)
FROM some_table t
JOIN (
SELECT player, MIN(game_date) AS min_date
FROM some_table
GROUP BY player
) a ON a.plyer = t.player AND a.min_date = t.game_date
GROUP BY t.player, t.game_date

Answer 3

Sub query approach of getting the result is given below
Filter the results only getting Player's first games.
Select min(Game_Date),Player from
basketball group by Player;
Use the results from first query to find each player's sum of scores in first game.
Select Game_Date, Player,sum(points) as first_play_points from
basketball where (Game_date,Player) in (Select min(Game_Date),Player
from basketball group by Player) group by Game_Date, Player;
Working fiddle can be found here