Question

首先，对不起标题，我不知道如何命名这个问题。

基本上，我正在根据位置和类别编写基本搜索引擎。

我有一个表事件，一个表events_categories和一个表类别。对象具有列城市和列状态

一个事件拥有并属于许多类别，一个类别拥有并属于许多事件。

我目前有以下查询：

select 
*
from events
LEFT OUTER JOIN "events_categories" 
ON "events_categories"."event_id" = "events"."id" 
LEFT OUTER JOIN "categories" 
ON "categories"."id" = "events_categories"."category_id" 
WHERE "categories"."id" = 2 
OR "categories"."id" = 3
order by city!='Paris', state!='TX'

它有效，但我想根据匹配的类别数量来订购我的结果，我也有重复的行。我想删除它们

这是the sqlfiddle I use

预期结果应为：

meetup＃2
meetup＃1
meetup＃4
meetup＃16
meetup＃5
meetup＃7
meetup＃8

Answer 1

这似乎做你想要的。虽然最后两行可能不是您需要的顺序，但这是因为这两行的所有排序条件的值都相同：

select events.id as event_id, 
       events.name as event_name,
       events.city,
       events.state,
       categories.id as category_id,
       categories.name as category_name,
       count(*) over (partition by events.id) as cat_count
from events
  LEFT JOIN events_categories ON events_categories.event_id = events.id
  LEFT JOIN categories ON categories.id = events_categories.category_id 
WHERE categories.id IN (2,3)
order by city <> 'Paris', 
         state <> 'TX',
         cat_count desc;

SQLFiddle：http://sqlfiddle.com/#!12/6c7a5/1

Answer 2

要按匹配类别的数量排序，您可以group by事件名称，然后按count(*) desc排序：

select  e.name
,       count(*)
from    events e
join    events_categories ec
on      ec.event_id = e.id
join    categories c
on      c.id = ec.category_id
where   c.id in (2,3)
group by
        e.name
order by 
        count(*) desc

Example at SQL Fiddle.

按匹配记录排序

2 个答案: