Great! 120k rows in 10 seconds on MySQL on Linux and 17 seconds on MS Access
in reply to Re^5: find difference in dates/items in same column
in thread find difference in dates/items in same column
(there's no 'day' parameter mysql's DATEDIFF - when i cracked that it worked!)
Your solution is vastly superior (simpler/faster) to the one in MYSQL cookbook or any SQL forum/discussion I have seen!
datediff( date, (select max(T2.date)
from test as T2
where T1.brand = T2.brand
and T2.date < T1.date) )
from test as T1
order by brand, id
Thanks that's great!