mysql - MySQL 中的百分比

Question

使用这个查询，

SELECT company, YEAR( date )  as year, COUNT( * ) as total
FROM table
WHERE company = "Medtronic"
OR company = "Private"
GROUP BY YEAR( date )

我得到一个这样的表:

Company         year    total
Medtronic   1998    6
Private     1998    5
Medtronic   1999    5
Private     1999    1

如何计算每家公司每年贡献的百分比？

例如，美敦力在 1998 年的贡献百分比是6/(6+5) = 54.5%

我一直在尝试通过 MySQL 查询来计算百分比。

谢谢你们。

Answer 1

使用:

SELECT x.company,
       x.year,
       x.annual_total
       x.annual_total / y.total AS percentage
  FROM (SELECT t.company, 
               YEAR(t.date) as year, 
               COUNT( * ) as annual_total
          FROM TABLE t
         WHERE t.company IN ('Medtronic', 'Private')
      GROUP BY YEAR( t.date ) ) x
  JOIN (SELECT t.company,
               COUNT(*) 'total'
          FROM TABLE t
         WHERE t.company IN ('Medtronic', 'Private')
      GROUP BY t.company) y ON y.company = x.company

如果您想要带有特定小数位的百分比，请使用:

CAST(x.annual_total / y.total AS DECIMAL(2,2)) AS percentage

检查这是否给出了您期望的每个公司的计数:

  SELECT t.company,
         COUNT(*) 'total'
    FROM TABLE t
   WHERE t.company IN ('Medtronic', 'Private')
GROUP BY t.company