SQL-如何获得2个总和的百分比

Question

我正在尝试使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，因此收到0（查看随附的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而不是您期望的1.5 ：

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

从小提琴中可以看出，解决该问题的方法是确保在进行除法运算之前将值强制转换/转换为浮点数。

Answer 2

也将结果转换为十进制：

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;

的* 1.0是避免整数除法的问题（即， 1/2=0 ，而不是1.5 。的NULLIF()是由零，以避免分裂。