SQL要为我的订户选择唯一域计数？

Question

我试图找出我从每个域都有用户数量，雅虎，谷歌，AOL的....

这里是我想出了但不分组，因为我认为这将

select SUBSTRING(EmailAddress, PATINDEX('%@%', EmailAddress) +1, LEN(EmailAddress) -PATINDEX('%@%', EmailAddress)) As [Domain], COUNT(SUBSTRING(EmailAddress, PATINDEX('%@%', EmailAddress) +1, LEN(EmailAddress) - PATINDEX('%@%', EmailAddress))) As [Count] 
from Subscribers 
GROUP BY EmailAddress 

结果是这样的

yahoo.com 1 
gmail.com 1 
yahoo.com 1 

我想要的东西更多类似这样的

yahoo.com 2 
gmail.com 1 

Answer 1

问题是，您正在按emailaddress分组，这不是domain的值。如果电子邮件地址包含john@yahoo.com或jim@yahoo.com，因为这些地址是唯一的，所以当您将组计数分隔时。

如果你想组由域值，那么你需要GROUP BY你计算formala域：

select SUBSTRING(EmailAddress, PATINDEX('%@%', EmailAddress) +1, LEN(EmailAddress) -PATINDEX('%@%', EmailAddress)) As [Domain], 
    COUNT(SUBSTRING(EmailAddress, PATINDEX('%@%', EmailAddress) +1, LEN(EmailAddress) - PATINDEX('%@%', EmailAddress))) As [Count] 
from Subscribers 
GROUP BY SUBSTRING(EmailAddress, PATINDEX('%@%', EmailAddress) +1, LEN(EmailAddress) -PATINDEX('%@%', EmailAddress)); 

或者你可以通过domain别名使用子查询，然后组：

select domain, 
    count(*) [count] 
from 
(
    select SUBSTRING(EmailAddress, PATINDEX('%@%', EmailAddress) +1, LEN(EmailAddress) -PATINDEX('%@%', EmailAddress)) As [Domain] 
    from Subscribers 
) d 
group by domain;