SQL面试题练习 —— 截止目前登陆用户数及登陆用户列表

题目来源：滴滴

1 题目

已知有用户登录记录表包含登录日期和登录用户ID，请查询出截止到当前日期累积登录用户数及登陆用户列表。

样例数据

+-------------+----------+
|  log_date   | user_id  |
+-------------+----------+
| 2024-01-01  | a        |
| 2024-01-02  | a        |
| 2024-01-02  | b        |
| 2024-01-03  | b        |
| 2024-01-04  | c        |
| 2024-01-05  | b        |
| 2024-01-05  | c        |
| 2024-01-05  | d        |
| 2024-01-05  | e        |
+-------------+----------+
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期望结果

+-------------+-----------+------------------------+
|  log_date   | user_cnt  |       user_list        |
+-------------+-----------+------------------------+
| 2024-01-01  | 1         | ["a"]                  |
| 2024-01-02  | 2         | ["a","b"]              |
| 2024-01-03  | 2         | ["a","b"]              |
| 2024-01-04  | 3         | ["a","b","c"]          |
| 2024-01-05  | 5         | ["a","b","c","d","e"]  |
+-------------+-----------+------------------------+
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2 建表语句

-- 建表语句
CREATE TABLE t_user_login
(
log_date STRING,
user_id STRING)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ','
STORED AS TEXTFILE;
-- 数据插入语句
INSERT INTO t_user_login
(log_date, user_id) VALUES
('2024-01-01','a'),
('2024-01-02','a'),
('2024-01-02','b'),
('2024-01-03','b'),
('2024-01-04','c'),
('2024-01-05','b'),
('2024-01-05','c'),
('2024-01-05','d'),
('2024-01-05','e');
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3 题解

（1）数据去重聚合

select log_date,
       user_id,
       count(distinct user_id) over (order by log_date asc) as user_cnt,
       collect_set(user_id) over (order by log_date asc)    as user_list
from t_user_login
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执行结果

+-------------+----------+-----------+------------------------+
|  log_date   | user_id  | user_cnt  |       user_list        |
+-------------+----------+-----------+------------------------+
| 2024-01-01  | a        | 1         | ["a"]                  |
| 2024-01-02  | b        | 2         | ["a","b"]              |
| 2024-01-02  | a        | 2         | ["a","b"]              |
| 2024-01-03  | b        | 2         | ["a","b"]              |
| 2024-01-04  | c        | 3         | ["a","b","c"]          |
| 2024-01-05  | e        | 5         | ["a","b","c","e","d"]  |
| 2024-01-05  | d        | 5         | ["a","b","c","e","d"]  |
| 2024-01-05  | c        | 5         | ["a","b","c","e","d"]  |
| 2024-01-05  | b        | 5         | ["a","b","c","e","d"]  |
+-------------+----------+-----------+------------------------+
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（2）分组得到结果

select log_date,
       user_cnt,
       user_list
from (select log_date,
             user_id,
             count(distinct user_id) over (order by log_date asc)          as user_cnt,
             sort_array(collect_set(user_id) over (order by log_date asc)) as user_list
      from t_user_login) t
group by log_date, user_cnt, user_list
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执行结果

+-------------+-----------+------------------------+
|  log_date   | user_cnt  |       user_list        |
+-------------+-----------+------------------------+
| 2024-01-01  | 1         | ["a"]                  |
| 2024-01-02  | 2         | ["a","b"]              |
| 2024-01-03  | 2         | ["a","b"]              |
| 2024-01-04  | 3         | ["a","b","c"]          |
| 2024-01-05  | 5         | ["a","b","c","d","e"]  |
+-------------+-----------+------------------------+
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