How to count the difference between two values in SQL? - sql

Question

Sorry if my title is not detailed
I have two tables
Game table:
homeTeam int
awayTeam int
homePoints int
awayPoints int
Team
tid int
name varchar(20)
I am trying to find the number of games won at home by a specific team, lets say 'cops', with Team.tid = Game.homeTeam and wins are counted if homePoints > awayPoints
I want to end up with
Team HomeWins
-----------------
Cops 20
How do I go about that?
EDIT: #
I Managed to get my answer using
SELECT t.name, count(CASE WHEN homePoints > awayPoints then 1 ELSE NULL END) as "Home Wins"
from Team t
JOIN Game g
ON t.tid = g.homeTeam
where t.name = 'Patriots'
GROUP BY t.name
some of the other answers were giving me the following errors
Column 'team.name' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

Answer 1

You should join the tables to be able to get both name and homePoints and use COUNT by homePoints and group by using team id to see a result for each team.
SELECT
T.name, COUNT(G.homePoints)
FROM
team T
INNER JOIN
game G ON G.homeTeam = T.tid
WHERE
G.homePoints > G.awayPoints
GROUP BY T.tid, T.name;
OR if you need the result for a specific team by providing it's id, you may drop the GROUP BY and add condition in the WHERE, e.g.
SELECT
T.name, COUNT(T.tid)
FROM
team T
INNER JOIN
game G ON G.homeTeam = T.tid
WHERE
G.homePoints > G.awayPoints and T.tid = :request_team_id;

Answer 2

First SELECT the columns that we want to display and use AS to specify they headings.
SELECT
team.name as 'Team',
COUNT(game.homePoints) AS 'HomeWins'
FROM dbo.team
Then we use INNER JOIN to only include the entries in game table, which match the Team ID in the homeTeam column vs what we selected from the team table.
INNER JOIN game on team.tid = game.homeTeam
Then we add a WHERE clause to limit it to only the team we ask for team.name = 'cops' and only include wins by that team
WHERE
team.name = 'cops'
AND game.homePoints > game.awayPoints
So all together your script should look like this;
SELECT
team.name as 'Team',
COUNT(game.homePoints) AS 'HomeWins'
FROM dbo.team
INNER JOIN game on team.tid = game.homeTeam
WHERE
team.name = 'cops'
AND game.homePoints > game.awayPoints
GROUP BY team.name