SQL查询以查找具有相同电子邮件域的最大计数

Question

我有一个电子邮件ID列，用于存储完整的电子邮件ID。我希望得到基于域的最大数量，即@ gmail.com，@ xyz.com似乎在GROUP BY子句中我们不能应用任何通配符，只考虑完整电子邮件地址中的域。

Answer 1

对于Mysql

SELECT SUBSTRING_INDEX(EMail.EMail, '@', -1) AS `Email Domain`, COUNT(*)
FROM EMail
GROUP BY SUBSTRING_INDEX(EMail.EMail, '@', -1)

有数据示例

SELECT SUBSTRING_INDEX(EMail.EMail, '@', -1) AS `Email Domain`, COUNT(*)
FROM
  (
  select '[email protected]' as EMail
  UNION
    SELECT '[email protected]'
    union
    select '[email protected]'
    union
      select '[email protected]'
  ) as EMail

  GROUP BY SUBSTRING_INDEX(EMail.EMail, '@', -1)

对于SQL服务器

SELECT RIGHT(Email, LEN(Email) - CHARINDEX('@', email)) Domain ,
COUNT(Email) EmailCount
FROM   dbo.email
WHERE  LEN(Email) > 0
GROUP BY RIGHT(Email, LEN(Email) - CHARINDEX('@', email))
ORDER BY EmailCount DESC