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Re^4: For a better efficiency and speed question!

by Anonymous Monk
on Oct 04, 2011 at 17:17 UTC ( #929601=note: print w/ replies, xml ) Need Help??


in reply to Re^3: For a better efficiency and speed question!
in thread For a better efficiency and speed question!

What is wrong with this code?

=code my $sql = $dbh->exec_select(" SELECT acc, name,date FROM mytable WHERE name <> '' AND ((date + 1 YEAR) >= (CURRENT_DATE)) AND ((date + 1 YEAR) < (CURRENT_DATE + 240 DAYS)) AND controlnum IN ('12345','8877788','23334455','223445988','222339000 +','2222333','223475699','22339668','2223999','009999','11220000','777 +66','88776' ,'9988888','11223756','22388577','9998888','998888','77665555','999988 +8','88877777','666555555','88777766666','112223333','9998877','998887 +7' ,'888777666666','00988777','887777654') and date between '2010-11-11' and '2011-11-11' order by date desc"); =cut
If you show where you see the error it would help! Thanks


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Re^5: For a better efficiency and speed question!
by pvaldes (Chaplain) on Oct 04, 2011 at 18:11 UTC

    Nothing wrong really, but you ask for efficiency and speed, and anything counts...

    You use: AND ((date + 1 YEAR) < (CURRENT_DATE + 240 DAYS))

    Let's see the algoritm. For each record you sum 365 to date and remember this number, then you sum 240 to current date and save this to a new var somewhere in the memory, then you compare both numbers

    I'm suggesting this instead: AND ((date + 125 DAYS) < CURRENT_DATE)

    Now for each record you sum 125 to date and compare this with current date. You are creating a new var, not two.

    Thus you need less memory and is also a little less demanding operation for the CPU. Nothing to care for when you have a few sums but in this context could suppose one advantage

      And now for the sql question, if not done yet, you should index or reindex your table (the controlnum field is a good candidate to be in the index) and probably use some views in order to check only a part of your table, and simplify the work to perl.
        I didn't understand your logic behind sum of 125 to "date"??

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