SQL-如何获得2个总和的百分比

Question

我正在尝试将点击率从上传到点击。我将如何获得这个百分比？

我目前正在使用下面的代码，因此我收到0（查看附件img）。

SELECT  geo_country, [created_at:date:aggregation] AS day,
  SUM(case when name = 'adclick' then 1 else 0 end) as clicks,
  SUM(case when name = 'camera_upload_image' then 1 else 0 end) as uploads,
  CONVERT(DECIMAL(10,2), clicks / NULLIF(uploads, 0)) As CTR
FROM events

结果：

Answer 1

您遇到的是整数除法。

如果取2个整数

clicks = 3 
uploads = 2

然后clicks / uploads等于1-不等于您期望的1.5：

http://sqlfiddle.com/#!18/0ed4a9/8/0

正如您从小提琴中看到的那样，解决该问题的方法是确保在进行除法运算之前将您的值强制转换/转换为浮点数。

Answer 2

还将您的结果转换为十进制：

SELECT  geo_country, [created_at:date:aggregation] AS day,
  SUM(case when name = 'adclick' then 1 else 0 end) as clicks,
  SUM(case when name = 'camera_upload_image' then 1 else 0 end) as uploads,
  CONVERT(DECIMAL(10,2), CONVERT(DECIMAL(10,2),clicks) / NULLIF(CONVERT(DECIMAL(10,2),uploads), 0)) As CTR
FROM events

Answer 3

使用子查询或CTE：

SELECT c.*, clicks * 1.0 / NULLIF(uploads, 0) as ratio
FROM (SELECT geo_country, [created_at:date:aggregation] AS day,
             SUM(case when name = 'adclick' then 1 else 0 end) as clicks,
             SUM(case when name = 'camera_upload_image' then 1 else 0 end) as uploads
      FROM events
      GROUP BY geo_country, [created_at:date:aggregation]
     ) c;

* 1.0避免整数除法问题（即1/2=0而不是1.5。NULLIF()避免除零。