Mysql 如何在不同行上的日期之间获取记录？

我有一个名为

Event

的表，它记录多玩家服务器上的玩家登录和注销时的情况

+----------------------------------------------+
| id | username | type   | timestamp           |
+----------------------------------------------+
| 1  | Player3  | login  | 2014-01-14 17:00:00 |
| 2  | Player4  | login  | 2014-01-14 17:00:00 |
| 3  | Player4  | logout | 2014-01-14 17:30:00 |
| 4  | Player1  | login  | 2014-01-14 18:00:00 |
| 5  | Player2  | login  | 2014-01-14 19:00:00 |
| 6  | Player3  | logout | 2014-01-14 19:00:00 |
| 7  | Player1  | logout | 2014-01-14 20:00:00 |
| 8  | Player2  | logout | 2014-01-14 20:00:00 |
+----------------------------------------------+

我想为那些在特定时间戳在线的人提供一个唯一的用户名列表。例如，如果我想知道谁在

2014-01-14 18:00:00

在线，它应该返回：

Player1

和

Player3

到目前为止，我所尝试的：

SELECT * FROM event 
WHERE (timestamp <= '2014-01-14 18:00:00' AND type = 'login')
AND (timestamp >= '2014-01-14 18:00:00' AND type = 'logout');

---

这比您的查询更复杂。您需要的人员在当时的最新操作是登录，基本上：

SELECT username,
       max(case when type = 'login' and timestamp <= '2014-01-14 18:00:00'
                then timestamp
           end) as lastlogin,
       max(case when type = 'logout' and timestamp <= '2014-01-14 18:00:00'
                then timestamp
           end) as lastlogout
FROM event 
GROUP BY username
HAVING (lastlogout is null or lastlogout < lastlogin) and lastlogin is not null;

选择用户名，
最大值（类型为'login'和时间戳时的情况）
您可以将时间戳配对为intime和outtime，然后查看指定的时间是否介于这两个时间之间

或者您可以使用
HAVING
取出1级子查询

SELECT username,timestamp as intime,
 (SELECT min(timestamp)
 FROM event e2
 WHERE e2.username = e1.username
 AND e2.timestamp > e1.timestamp
 AND e2.type = 'logout') as outtime
FROM event e1
WHERE e1.type = 'login'
HAVING '2014-01-14 18:00:00' BETWEEN intime AND outtime;

谢谢！我希望登录/注销记录是准确的。但是，如果表中有很多记录，哪一个性能更好？这两个查询的性能应该类似。您可以通过在
timestamp
上放置索引并在第一个版本中添加where子句来提高性能，例如
where timestamp在'201之间4-01-13'和'2014-01-14 18:00:00'
（假设用户登录时间不超过42小时）。这将显著减少数据量。您能看一下我的编辑吗？我有另一个名为Session的表，从该表中查询是否更好？
SELECT username,
       sum(type = 'login' and timestamp <= '2014-01-14 18:00:00') as numlogins,
       sum(type = 'logout' and timestamp <= '2014-01-14 18:00:00') as numlogouts
FROM event 
GROUP BY username
HAVING numlogins > numlogouts;

SELECT lie.username
from session s join
     event lie
     on s.login_event = lie.id join
     event loe
     on s.logout_event = loe.id
where lie.timestamp <= '2014-01-14 18:00:00' and
      loe.timestamp >= '2014-01-14 18:00:00';

SELECT username FROM
(SELECT username,timestamp as intime,
       (SELECT min(timestamp)
        FROM event e2
        WHERE e2.username = e1.username
          AND e2.timestamp > e1.timestamp
        AND e2.type = 'logout') as outtime
FROM event e1
WHERE e1.type = 'login'
)t1
WHERE '2014-01-14 18:00:00' BETWEEN t1.intime AND t1.outtime;

SELECT username,timestamp as intime,
 (SELECT min(timestamp)
 FROM event e2
 WHERE e2.username = e1.username
 AND e2.timestamp > e1.timestamp
 AND e2.type = 'logout') as outtime
FROM event e1
WHERE e1.type = 'login'
HAVING '2014-01-14 18:00:00' BETWEEN intime AND outtime;