如何编写以下SQL查询

Question

I am on a MYSQL DB with the following schema.

id bigint(20)
url varchar(500)
timestamp datetime
server varchar(500)

I need to write a query to find all which url gets switched by two different servers in an hour or more.

So for instance if url1 gets served by server1 at 11:00 and gets served by server2 at 12:00 then it should be in the result, however if url2 gets served by server1 at 11:05 and by server2 at 11:30 then it should not be in the result.

Please find the sample fiddle here Fiddle . In this case the output should be www.url2.com .

Answer 1

just use timestampdiff function in a where exists...subquery :

select distinct url 
from sample s1
where exists (
     select url 
     from sample s2 
     where 
     s2.url=s1.url
     and timestampdiff(HOUR, s2.timestamp, s1.timestamp)>=1
    )

SQLFIDDLE DEMO