Question

我有一张表格，其中包含所有用户的视频下载历史记录：

src_ip   vlan_id  video_id area  date_pl
aaaa     A        1        123   xxxx-xx-xx
aaaa     A        2        123   xxxx-xx-xx
aaaa     B        1        456   xxxx-xx-xx
bbbb     A        4        123   xxxx-xx-xx
bbbb     C        6        567   xxxx-xx-xx
...

我使用src_ip和vlan_id的组合来识别不同的用户，现在我想随机选择50个不同的用户（这意味着50个不同的src_ip和vlan_id组合）并列出他们的所有下载历史记录。

首先我做了：

   SELECT distinct src_ip, vlan_id from video_2 as table2 
   WHERE date_pl >= '2011-11-29 00:00' AND date_pl <= '2011-12-05 23:55' order by rand() limit 50

然后我做了：

   SELECT src_ip, vlan_id, video_id, area from video_2 
   where video_2.src_ip = table2.src_ip AND video_2.vlan_id = table2.vlan_id 
   AND date_pl >= '2011-11-29 00:00' AND date_pl <= '2011-12-05 23:55'

但问题是，因为它们是两个独立的查询，所以在第二个查询中，它不知道table2是什么。

如何解决此问题或如何将这两个查询合并为一个？

Answer 1

CREATE TEMPORARY TABLE table2
AS
SELECT distinct src_ip, vlan_id from video_2
WHERE date_pl >= '2011-11-29 00:00' AND date_pl <= '2011-12-05 23:55'
ORDER BY rand() 
LIMIT 50;

SELECT src_ip, vlan_id, video_id, area
FROM 
   video_2
   JOIN 
   table2 ON video_2.src_ip = table2.src_ip AND video_2.vlan_id = table2.vlan_id';

由于限制在子查询中使用LIMIT，无法使“table2”在行~~中派生。否则就是~~

SELECT 
   v2.src_ip, v2.vlan_id, v2.video_id, v2.area 
FROM 
   video_2 v2
   JOIN 
   (SELECT distinct v.src_ip, v.vlan_id from video_2 v
   WHERE v.date_pl >= '2011-11-29 00:00' AND v.date_pl <= '2011-12-05 23:55'
   ORDER BY rand() 
   LIMIT 50
   ) table2 ON v2.src_ip = table2.src_ip AND v2.vlan_id = table2.vlan_id;

编辑：限制子查询中的LIMIT主要适用于IN，而不适用于派生表

编辑2：添加了更多别名

在Mysql中合并两个查询

1 个答案: