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From Harshad <harshad...@gmail.com>
Subject Re: Performance issue of derby using JDBC
Date Mon, 15 Dec 2008 19:14:40 GMT
Bryan Pendleton wrote:

> Harshad wrote:
>>   "select name,version,release,time from PKG where PKG.id in (select id
>>   from PROVIDES where name = ?)",
> What happens if you run this statement instead:
> select pkg.name,pkg.version,pkg.release,pkg.time from pkg, provides
>         where pkg.id = provides.id and provides.name = ?

Whew! That solves it! No need for numbers, they are sub milli-second now!

Can't the SQL optimiser do this automatically? Is this a derby specific problem?  (Sorry for
amateurish questions; this is my first real db application)

I ask because I have another application where I programmatically generate queries, and the
former type of query is easier to generate than the one you suggested. I always assumed that
the SQL optimiser will "flatten" the query...


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