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Re^6: find difference in dates/items in same column

by zerocred (Beadle)
on Nov 15, 2008 at 22:04 UTC ( #723854=note: print w/replies, xml ) Need Help??


in reply to Re^5: find difference in dates/items in same column
in thread find difference in dates/items in same column

Great! 120k rows in 10 seconds on MySQL on Linux and 17 seconds on MS Access
(there's no 'day' parameter mysql's DATEDIFF - when i cracked that it worked!)
select brand, id, date, 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
Your solution is vastly superior (simpler/faster) to the one in MYSQL cookbook or any SQL forum/discussion I have seen!
Thanks that's great!

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[Corion]: Eily: Sure - if you force both things into stringy things, then you break that magic. But that would also mean that you changed the expression, as now $x = 0.00 will be true instead of false as it were before
[Corion]: Ah no, at least in my feeble experiments that doesn't change the meaning
[Corion]: We sell sanity in small packages ;)
[Eily]: oh, boolean context uses the "" overload if no bool overload has been defined
[Eily]: (I wondered if overloading bool was actually necessary)

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