SQL：每年计算电子邮件数

Question

我想计算每年在我的数据库中发送的邮件数量。

我试过

SELECT Distinct year(RCM_DateSent) FROM Mail
ORDER BY RCM_DateSent

另外

SELECT COUNT(*)AS [Send], RCM_DateSent FROM Mail
GROUP BY RCM_DateSent 
ORDER BY [Send]

结果不是我想要的，我想知道每年可以发送电子邮件。

Answer 1

select year(rcm_dateSent) as yearSent, count(*) as numbersend
from mail
group by year(rcm_dateSent)
order by yearSent

Answer 2

你必须'按年分组'。像这样：

SELECT Year(RCM_DateSent) AS YearOfMail, count(*) AS TotalMailsSent  
FROM Mail  
GROUP BY Year(RCM_DateSent)  
ORDER BY Year(RCM_DateSent)

PS：最好在分组中使用年份（RCM_DateSent）和＆amp; order by，而不是别名。