Question

I have a table which has the following

id     timestamp
-------------------------------------
 1     1247046037
 4     1247047437
 5     1247047438
 6     1247048738

Now I want to return all those ids which are 3 minutes apart from the previous id. In the above example it should return 1,4,6.

How should I go about doing this? Kinda confused. I want to avoid joins and everything else as much as possible.

UPDATE Sorry, I forgot to mention that the IDs may not be sequential so cannot use id = id+1

Answer 1

You are not going to be able to do this without joins, as far as I can tell. This should do what you need

select t1.id
from mytable as t1
    left join mytable as t2 on t1.id = (t2.id + 1)
where t2.id is null or (t1.timestamp - 180) > t2.timestamp

If the id field may have gaps, you’ll need to introduce a row number field to do this. Probably more efficient to add an autonumber field to your table if you’ll be running this regularly.

select t1.id
from 
    (select mytable.*, @rownum:=@rownum+1 as rownum from mytable, (select @rownum:=0) r order by id) as t1
    left join 
    (select mytable.*, @rownum2:=@rownum2+1 as rownum from mytable, (select @rownum2:=0) r order by id) as t2 on t1.rownum = (t2.rownum + 1)
where t2.id is null or (t1.timestamp - 180) > t2.timestamp