Question

很抱歉，我找不到基本答案。

具有2列 car_type 和 event 的简单表格。每次客户询问汽车时，表中都会记录一条记录，并且event =“ inquire”。如果购买了该类型的汽车，则会放入事件=“购买”的记录。

如何根据＃购买/＃查询来计算哪种车型最成功？按课程类型分组。

我尝试过

select car_type, 
      ((select count(*) from TABLE where event = "bought" ) / 
       (select count(*) from alerts where event = "inquire") * 100.0) as percentage
from TABLE 
group by car_type;

但这没用。

提前谢谢！

Answer 1

您可以使用条件聚合：

select car,
       (sum( event = 'bought') /
        sum( event = 'inquire' )
       ) as bought_inquire_ratio
from t
group by car;

如果您只想总体购买比例，可以使用：

select car,
       avg( event = 'bought' )
from t
group by car;

Answer 2

您可以对每辆车的不同事件类型求和（最容易在子查询中），然后将结果除以得到百分比，按该值的降序排列并仅取最高值：

SELECT car_type, 100.0 * bought / inquiries AS percentage
FROM (
    SELECT car_type,
           SUM(event = 'bought') AS bought,
           SUM(event = 'inquire') AS inquiries
    FROM alerts
    GROUP BY car_type
) c
ORDER BY percentage DESC
LIMIT 1

根据一列中的值按组计算百分比

2 个答案: