On Fri, 09 Jan 2009 21:16:03 +0100, Lukas Haase
<lukasha...@gmx.at> wrote in General Discussion of SQLite
Database <sqlite-users@sqlite.org>:
>Hello Richard!
>
>Thank you very much!! It works! :-)
>
>
>Indeed. 0-10 milliseconds instead of 500-800 :-)
>
>But may you tell me why this works and where you have this information?
>I know the O-notation but I do not know /why/ this boosts down to log(n)...
Use EXPLAIN SELECT .....
to see the virtual machine instructions
and EXPLAIN SELECT QUERY PLAN .....
to see which index is used.
http://www.sqlite.org/lang_explain.html
Each JOIN is implemented as nested loops. The virtual
machine code can tell a lot about what part of the database
has to be scanned.
>I have other queries which worry me. But that trick did not help in
>these cases :-(
>
[...]
>
>Thank you again and best regards,
>Luke
--
( Kees Nuyt
)
c[_]
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