球队以及得分计算的SQL语句

select teams.*, 
       ISNULL(points.num_points,0) as num_points 
from teams left join 
    (select host_team,
            SUM(hostpoint) as num_points 
     from (select host_team,
                  (case when host_goals>guest_goals then 3 when host_goals=guest_goals then 1 else 0 end) as hostpoint
           from matches
           union
           select guest_team,
                  (case when host_goals>guest_goals then 0 when host_goals=guest_goals then 1 else 3 end) as guestpoint
           from matches) point 
     group by host_team) points 
on teams.team_id=points.host_team
order by points.num_points desc,teams.team_id asc