文章目录1. 题目2. 解题1. 题目Table: Teams
代码语言：javascript代码运行次数：0运行复制+---------------+----------+
| 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。Table: Matches
代码语言：javascript代码运行次数：0运行复制+---------------+---------+
| 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。
积分规则如下：
赢一场得三分；
平一场得一分；
输一场不得分。写出一条SQL语句以查询每个队的 team_id，team_name 和 num_points。
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：
代码语言：javascript代码运行次数：0运行复制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 |
+------------+--------------+---------------+-------------+--------------+
Result table:
+------------+--------------+---------------+
| 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 |
+------------+--------------+---------------+ 来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/team-scores-in-football-tournament
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2. 解题按照主队，客队分别计算完 合并，再group by，left join 队名表代码语言：javascript代码运行次数：0运行复制# Write your MySQL query statement below
select Teams.team_id, Teams.team_name, ifnull(Scores.score, 0) num_points
from Teams left join
(
select team, sum(score) score
from
(
(
select host_team team, (case when host_goals > guest_goals then 3
when host_goals = guest_goals then 1
else 0 end) score
from Matches
)
union all
(
select guest_team team, (case when host_goals > guest_goals then 0
when host_goals = guest_goals then 1
else 3 end) score
from Matches
)
) temp
group by team
) Scores
on Teams.team_id = Scores.team
order by num_points desc, team_id690 ms