使用SQL对列中的项进行计数

我正在尝试编写一个SQL查询，该查询将添加电子邮件地址在Transactions表的sender列和recipient列中的次数

所以

请求输出：

Email address  |  Sent  |  Received
xyz.com           3           1
sdz.com           1           0
abc.com           0           2
bac.com           0           1

到目前为止，我所拥有的：

SELECT Sender, COUNT(Sender) as 'Total Sent', COUNT(recipient) as 'Total 
Received'
FROM Transactions (NOLOCK)
group by Sender
order by sender

---

谢谢你的帮助

您可以使用

全部联合

和聚合

select email_address
,count(case when type='Sent' then 1 end) as sent
,count(case when type='Received' then 1 end) as received
from (SELECT Sender as email_address,'Sent' as type
      FROM Transactions 
      UNION ALL
      SELECT Receiver,'Received'
      FROM Transactions 
     ) t
group by email_address

---

你可以用一笔钱来证明，当你和工会都收到邮件的时候

    select Email_address 
        , sum(case when  t_type = 'Sender', then 1 else 0 end) sent
        , sum(case when  t_type = 'Receipient', then 1 else 0 end) Receipient
    from (
        select 'Sender' t_type,   Sender as sent
        from Transactions
        union All
        select 'Receipient' t_type,  Recipient
        from Transactions ) t
    group by Email_address

---

由于您正在进行两个不同的分组，我建议您自行加入，如：

SELECT a.Sender, COUNT(a.Sender) AS 'Total Sent',  b.recieved AS 'Total 
Received'
FROM Transactions
JOIN (SELECT Receipient, COUNT(Receipient) AS recieved 
      FROM Transactions
      GROUP BY b.Receipient) b ON b.Receipient=a.Sender
GROUP BY a.Sender

---

如果要使用表提示，则不推荐省略with关键字。当然，NOLOCK暗示了一个许多人并不完全理解的滑坡。

SELECT a.Sender, COUNT(a.Sender) AS 'Total Sent',  b.recieved AS 'Total 
Received'
FROM Transactions
JOIN (SELECT Receipient, COUNT(Receipient) AS recieved 
      FROM Transactions
      GROUP BY b.Receipient) b ON b.Receipient=a.Sender
GROUP BY a.Sender