Calculating the win/loss ratio per team

I have the following two tables:

sport_a_statistics:

id      team_id     game_id     points
1       1           1           7   
2       2           1           8
3       3           2           6   
4       1           2           9

sport_b_statistics:

id      team_id     game_id     points
1       1           3           2   
2       2           3           1
3       3           4           3   
4       1           4           10

I want to calculate the win/loss ratio for each team. This includes making sure to capture the wins and losses from both sport tables since my tournament involves 2 sports. So the output I’m looking for is the following:

team_id    wins    loss    ratio
1          3       1       3.0
2          1       1       1.0
3          0       2       0.0

I can’t wrap my head around how I would do this in one query.

Answer

Assuming you have no ties, you can use window functions and union all:

select team_id,
       sum(points = max_points) as num_wins,
       sum(points < max_points) as num_losses,
       sum(points = max_points) / nullif(sum(points < max_points), 0) as ratio
from ((select a.*, max(points) over (partition by game_id) as max_points
       from sport_a a
      ) union all
      (select b.*, max(points) over (partition by game_id) as max_points
       from sport_b b
      ) 
     ) ab
group by team_id

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Made a small edit ^