1212. 查询球队积分

SQL架构

表: Teams

+---------------+----------+
| Column Name   | Type     |
+---------------+----------+
| team_id       | int      |
| team_name     | varchar  |
+---------------+----------+
此表的主键是 team_id。
表中的每一行都代表一支独立足球队。

表: Matches

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| match_id      | int     |
| host_team     | int     |
| guest_team    | int     | 
| host_goals    | int     |
| guest_goals   | int     |
+---------------+---------+
此表的主键是 match_id。
表中的每一行都代表一场已结束的比赛。
比赛的主客队分别由它们自己的 id 表示，他们的进球由 host_goals 和 guest_goals 分别表示。

您希望在所有比赛之后计算所有球队的比分。积分奖励方式如下:

• 如果球队赢了比赛(即比对手进更多的球)，就得 3 分。
• 如果双方打成平手(即，与对方得分相同)，则得 1 分。
• 如果球队输掉了比赛(例如，比对手少进球)，就 不得分 。

写出一条SQL语句以查询每个队的 team_id，team_name 和 num_points。

返回的结果根据 num_points 降序排序，如果有两队积分相同，那么这两队按 team_id  升序排序。

查询结果格式如下。

示例 1:

输入：
Teams table:
+-----------+--------------+
| team_id   | team_name    |
+-----------+--------------+
| 10        | Leetcode FC  |
| 20        | NewYork FC   |
| 30        | Atlanta FC   |
| 40        | Chicago FC   |
| 50        | Toronto FC   |
+-----------+--------------+
Matches table:
+------------+--------------+---------------+-------------+--------------+
| match_id   | host_team    | guest_team    | host_goals  | guest_goals  |
+------------+--------------+---------------+-------------+--------------+
| 1          | 10           | 20            | 3           | 0            |
| 2          | 30           | 10            | 2           | 2            |
| 3          | 10           | 50            | 5           | 1            |
| 4          | 20           | 30            | 1           | 0            |
| 5          | 50           | 30            | 1           | 0            |
+------------+--------------+---------------+-------------+--------------+
输出：
+------------+--------------+---------------+
| team_id    | team_name    | num_points    |
+------------+--------------+---------------+
| 10         | Leetcode FC  | 7             |
| 20         | NewYork FC   | 3             |
| 50         | Toronto FC   | 3             |
| 30         | Atlanta FC   | 1             |
| 40         | Chicago FC   | 0             |
+------------+--------------+---------------+

union all: 

select
t.team_id,t.team_name,ifnull(sss1.num_points,0) num_points
from
Teams t left join
(
select
team_id,sum(num_points) num_points
from
(
select
host_team team_id,sum(case 
when host_goals > guest_goals then 3
when host_goals = guest_goals then 1
when host_goals < guest_goals then 0
end) num_points
from
Matches
group by
match_id
union all
select
guest_team team_id,sum(case 
when host_goals > guest_goals then 0
when host_goals = guest_goals then 1
when host_goals < guest_goals then 3
end) num_points
from
Matches
group by
match_id
) ss1
group by 
team_id
)sss1
on t.team_id = sss1.team_id
order by 
num_points desc,team_id

if 嵌套 :

select
team_id, team_name,ifnull(sum(if(team_id=host_team,host_score,guest_score)),0) as num_points
from Teams m  
left join
(
select host_team, guest_team, 
if(host_goals<guest_goals,0,if(host_goals>guest_goals,3,1)) as host_score, 
if(host_goals<guest_goals,3,if(host_goals>guest_goals,0,1)) as guest_score
from Matches) t 
on m.team_id = t.host_team or m.team_id = t.guest_team 
group by team_id
order by num_points desc, team_id