# 1126.(Medium)查询活跃业务

事件表：Events

```
+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| business_id   | int     |
| event_type    | varchar |
| occurences    | int     | 
+---------------+---------+
此表的主键是 (business_id, event_type)。
表中的每一行记录了某种类型的事件在某些业务中多次发生的信息。
```

写一段 SQL 来查询所有活跃的业务。

如果一个业务的某个事件类型的发生次数大于此事件类型在所有业务中的平均发生次数，并且该业务至少有两个这样的事件类型，那么该业务就可被看做是活跃业务。

查询结果格式如下所示：

```
Events table:
+-------------+------------+------------+
| business_id | event_type | occurences |
+-------------+------------+------------+
| 1           | reviews    | 7          |
| 3           | reviews    | 3          |
| 1           | ads        | 11         |
| 2           | ads        | 7          |
| 3           | ads        | 6          |
| 1           | page views | 3          |
| 2           | page views | 12         |
+-------------+------------+------------+

结果表
+-------------+
| business_id |
+-------------+
| 1           |
+-------------+ 
'reviews'、 'ads' 和 'page views' 的总平均发生次数分别是 (7+3)/2=5, (11+7+6)/3=8, (3+12)/2=7.5。
id 为 1 的业务有 7 个 'reviews' 事件（大于 5）和 11 个 'ads' 事件（大于 8），所以它是活跃业务。
```

来源：力扣（LeetCode）

链接：<https://leetcode-cn.com/problems/active-businesses>

著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

## Solution

```sql
with t as (
    select event_type, avg(occurences) avg_ocr
    from Events
    group by event_type
)

-- solution 1
select business_id
from Events left join t using(event_type)
group by business_id
having sum(occurences > avg_ocr) >=2

-- solution 2
select business_id
from Events inner join t on Events.event_type=t.event_type and Events.occurences > t.avg_ocr
group by 1
having count(1) >=2
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://zqt0.gitbook.io/leetcode/sql/1126.active-businesses.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.