在 Mysql 中合并两个查询 [英] Merge two queries in Mysql

问题描述

我有一个包含所有用户视频下载历史记录的表格:

I have a table which includes all the users video downloading history:

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 src_ip 和 vlan_id 的 50 个不同的组合)并列出他们所有的下载历史.

I use the combination of src_ip and vlan_id to identify different users, Now I want to randomly select 50 different users (which means 50 distinct combinations of src_ip and vlan_id )and list all their downloading history.

所以我首先做了:

   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

然后我做到了:

   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，由于它们是两个独立的查询，在第二个查询中，它不知道 table2 是什么.

But the problem is, since they are two independent queries, in the second query, it doesn't know what table2 is.

我该如何解决这个问题或者如何将这两个查询合二为一?

How can I solve this problem or how to merge these two queries into one?

推荐答案

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';

您可以 不能在行中派生table2"，因为限制在子查询中使用LIMIT.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;

子查询中的限制 LIMIT 主要适用于 IN，而不适用于派生表

Restrictions LIMITs in subqueries apply to IN mostly, not derived tables

编辑 2:添加了更多别名

Edit 2: added more aliases

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