如何区分两个求和查询

Question

我必须计算足球队的目标差异.基本上它是:(goalsScoredAtHome + goalsScoredAway) - (goalsConciededAtHome + goalsConciededAway)一切都保存在一个表中:

homeTeam | awayTeam | goalsHome | goalsAway
  USA    |  Poland  |     2     |    0
 Poland  |   USA    |     3     |    1

这是我有4个单独的查询:

(select sum(goalsHome) as GoalsScoredHome from game where home = 'USA' 
+
select sum(goalsAway) as GoalsScoredAway from game where away = 'USA')
-
(select sum(goalsAway) as GoalsConciededHome from game where home = 'USA'
+
select sum(goalsHome) as GoalsConciededAway from game where away = 'USA')

有没有办法在一个查询中执行此操作？

Answer 1

查询的直接翻译使用条件聚合:

select (sum(case when home = 'USA' then goalsHome else 0 end) +
        sum(case when away = 'USA' then goalsAway else 0 end)
       ) -
       (sum(case when home = 'USA' then goalsAway else 0 end) +
        sum(case when away = 'USA' then goalsHome else 0 end)
       )
from game;

您可以将其简化为:

select (sum(case when home = 'USA' then goalsHome - goalsAway else 0 end) +
        sum(case when away = 'USA' then goalsAway - goalsHome else 0 end)
       )
from game;