Question

我正在使用MySQL和Visual Basic开发一个登录/退出表单。我现在的查询只显示每个用户的最新事件，但我希望显示前两个事件（即：他/她何时登录以及何时退出。

我有一个名为event的表，其中包含以下字段：

Event_ID   
User_BannerID   
Class_ID   
Timestamp    
Status    
Creator

SELECT CONCAT(u.lastname, ', ', u.firstname) AS Name
   , s.class AS Class
   , DATE_FORMAT(e.timestamp,'%b %d %Y - %r') AS DateTime
   , e.status AS Status                
FROM event e, user u, status s   
WHERE e.user_bannerid = u.user_bannerid
   AND e.class_id = s.class_id
   AND event_id IN
   (
      SELECT MAX(event_id)
      FROM event e
      GROUP BY e.user_bannerid
   )
ORDER BY name

Answer 1

在SELECT语句中使用LIMIT子句并结合正确的ORDER BY：

SELECT ...
FROM theTable
WHERE ...
LIMIT 2
ORDER BY timestamp DESC

Answer 2

查看this article中名为“从每个组中选择前N行”的部分。

Answer 3

AND event_id IN
(
  SELECT event_id
  FROM (SELECT * FROM event ORDER BY event_id DESC LIMIT 2) e
)

变通方法的来源：http://forums.mysql.com/read.php?86,14788,14788及其回复，链接在底部。测试5.1

Mysql前2个事件查询

3 个答案: