Help SQL question (Calculation)

[David McKee]

Can someone please help. I am trying to calculate games behind but the query must be missing something (.5 games not showing up) (since not all teams always have same game count top team has played 2 games so teams that played 1 are not really 1 back they should be .5) similar

Current Results
Team GP Wins Losses Points PCT GB
A 2 2 0 4 1.000 0.0
B 1 1 0 2 1.000 0.0-Should be 0.5 (halfback)
C 1 1 0 2 1.000 0.0-Should be 0.5 (halfback)
D 1 1 0 2 1.000 0.0-Should be 0.5 (halfback)
E 1 0 1 1 0.000 1.0
F 1 0 1 1 0.000 1.0
G 1 0 1 1 0.000 1.0
H 2 0 2 2 0.000 2.0

My Code
SELECT
Team,
COUNT(*) AS GP,
SUM(is_win) AS Wins,
SUM(NOT is_win) AS Losses,
2 * SUM(is_win) + SUM(NOT is_win) AS Points,
truncate(SUM(is_win) / ((SUM(is_win)+(sum(NOT is_win)))), 3) AS PCT,
truncate((case when Count(*) - (sum(is_win) - sum(NOT is_win)) = 0 then 0
else (abs(Count(*) - (sum(is_win) - sum(NOT is_win))) / 2) end),1)as GB
FROM
(
SELECT
HomeTeam AS Team,
HomeScore > AwayScore AS is_win
FROM Games

UNION ALL
SELECT
AwayTeam AS Team,
HomeScore < AwayScore AS is_win
FROM Games

) T1
GROUP BY Team
ORDER BY Wins DESC, PCT DESC, Losses ASC