1.题目基本信息
1.1.题目描述
Table: Teams
±------------±--------+
| Column Name | Type |
±------------±--------+
| player_id | int |
| team_name | varchar |
±------------±--------+
player_id is the unique key for this table.
Each row contains the unique identifier for player and the name of one of the teams participating in that match.
Table: Passes
±------------±--------+
| Column Name | Type |
±------------±--------+
| pass_from | int |
| time_stamp | varchar |
| pass_to | int |
±------------±--------+
(pass_from, time_stamp) is the unique key for this table.
pass_from is a foreign key to player_id from Teams table.
Each row represents a pass made during a match, time_stamp represents the time in minutes (00:00-90:00) when the pass was made,
pass_to is the player_id of the player receiving the pass.
Write a solution to find the longest successful pass streak for each team during the match. The rules are as follows:
A successful pass streak is defined as consecutive passes where:
Both the pass_from and pass_to players belong to the same team
A streak breaks when either:
The pass is intercepted (received by a player from the opposing team)
Return the result table ordered by team_name in ascending order.
1.2.题目地址
https://leetcode.cn/problems/longest-team-pass-streak/description/
2.解题方法
2.1.解题思路
窗口函数+分组聚合
2.2.解题步骤
第一步，将team_name绑定到passes表格中，记字段flag为传球的状态（成功传球为0，失败为1），得到表格T1
第二步，使用窗口函数SUM，按team1分组、time_stamp进行升序排列，计算flag字段的前缀和，即为flag_prefix字段，得到表格T2
第三步，按team1,flag_prefix进行聚合，如果flag_prefix=0，COUNT()即为连续成功次数，否则COUNT()-1即为连续成功次数，记为字段streak，得到表格T3
第四步，按team_name进行分组聚合，统计streak的最大值记为longest_streak字段，即为题解
3.解题代码
sql代码
sql
# Write your MySQL query statement below
WITH T1 AS (
# 第一步，将team_name绑定到passes表格中，记字段flag为传球的状态（成功传球为0，失败为1），得到表格T1
SELECT
pass_from, time_stamp, pass_to,
t1.team_name AS team1,
IF(t1.team_name = t2.team_name, 0, 1) AS flag
FROM Passes
LEFT JOIN Teams AS t1 ON Passes.pass_from = t1.player_id
LEFT JOIN Teams AS t2 ON Passes.pass_to = t2.player_id
), T2 AS (
# 第二步，使用窗口函数SUM，按team1分组、time_stamp进行升序排列，计算flag字段的前缀和，即为flag_prefix字段，得到表格T2
SELECT
team1,
SUM(flag) OVER (PARTITION BY team1 ORDER BY time_stamp) AS flag_prefix
FROM T1
), T3 AS (
# 第三步，按team1,flag_prefix进行聚合，如果flag_prefix=0，COUNT(*)即为连续成功次数，否则COUNT(*)-1即为连续成功次数，记为字段streak，得到表格T3
SELECT
team1,
IF(flag_prefix = 0, COUNT(flag_prefix), COUNT(flag_prefix) - 1) AS streak
FROM T2
GROUP BY team1, flag_prefix
)
# 第四步，按team_name进行分组聚合，统计streak的最大值记为longest_streak字段，即为题解
SELECT
team1 AS team_name,
MAX(streak) AS longest_streak
FROM T3
GROUP BY team1
HAVING MAX(streak) != 0
ORDER BY team14.执行结果
