基于多列删除重复项(Deleting duplicates based on multiple columns)

 我使用以下内容列出了重复项： 
 
select s.MessageId, t.* 
from Message s
join (
    select ToUserId, FromUserId, count(*) as qty
    from Message
    group by ToUserId, FromUserId
    having count(*) > 1
) t on s.ToUserId = t.ToUserId and s.FromUserId = t.FromUserId
 
 现在，我该如何删除所有邮件（我试图删除重复邮件，以便在FromUserId and ToUserId上应用唯一索引）。 

I have listed duplicates using the following:
 
select s.MessageId, t.* 
from Message s
join (
    select ToUserId, FromUserId, count(*) as qty
    from Message
    group by ToUserId, FromUserId
    having count(*) > 1
) t on s.ToUserId = t.ToUserId and s.FromUserId = t.FromUserId
 
Now, how do I delete all but one of the Messages (I'm trying to remove duplicates so I can apply a unique index on FromUserId and ToUserId).

原文：https://stackoverflow.com/questions/41435527