Question

我有一个游戏服务器，我想得到一个最被忽视的玩家账户列表。

我有一个用户表

Table1 - Users:
Name    | ID | otherstuff
Troll   | 1  | .
CoolGuy | 2  | .

我有一个忽略表

Table2 - Ignores
id_UserWhoIsIgnoring | id_UserWhoIsIgnored
                   2 | 1
                   3 | 1

现在这一切都很棒，我可以这样做：

select
  u.name,
  ig.id_UserWhoIsIgnored,
  count(ig.id_UserWhoIsIgnored) as ignoreCount
from ignores ig
  inner join users u
  on ig.id_UserWhoIsIgnored = u.id
group by id_UserWhoIsIgnored
order by ignoreCount desc
limit 25;

但问题在于，我得到了很长时间内无法连接的用户的帐户。我想将查询限制为过去30天内连接的用户。我有第三张桌子sessions

Table3 - Sessions
id_user      | start_time          | otherstuff
1            | 2014-06-25 00:00:00 | .
(id)OldTroll | 2010-01-01 00:00:00 | .

如何组合我的第一个查询给出列表，但仅限于where start_time > date_sub(now(), interval 45 days)为我提供id的结果。在这种情况下，我不希望显示OldTroll的行，即使他们最被忽略，因为他们最近的连接已有数年之久。

Answer 1

如果start_time表中有users，那么只需使用where：

select u.name, ig.id_UserWhoIsIgnored, count(ig.id_UserWhoIsIgnored) as ignoreCount
from ignores ig inner join
     users u
     on ig.id_UserWhoIsIgnored = u.id
where start_time > date_sub(now(), interval 45 days)
group by id_UserWhoIsIgnored
order by ignoreCount desc
limit 25;

如果start_time表中有ignores，那么只需使用having：

select u.name, ig.id_UserWhoIsIgnored, count(ig.id_UserWhoIsIgnored) as ignoreCount
from ignores ig inner join
     users u
     on ig.id_UserWhoIsIgnored = u.id
group by id_UserWhoIsIgnored
having max(start_time) > date_sub(now(), interval 45 days)
order by ignoreCount desc
limit 25;

编辑：

然后我猜你想要：

select u.name, ig.id_UserWhoIsIgnored, count(ig.id_UserWhoIsIgnored) as ignoreCount
from ignores ig inner join
     users u
     on ig.id_UserWhoIsIgnored = u.id inner join
     (select id_user, max(start_time) as start_time
      from sessions
      group by id_user
     ) s
     on u.id_user = s.id_user and
        s.start_time >= date_sub(now(), interval 45 days)
group by id_UserWhoIsIgnored
order by ignoreCount desc
limit 25;

如果第三个表中的行匹配where子句，则进行双连接

1 个答案: