Обсуждение: restricting select statements

I'm working with JDBC and if I issue a broad SELECT statement, with a
good amount of records (2000) it takes quite a while to execute the
query and send the results back, even up to a minute, when I only want
about the first 100 records. If I restrict the search, it is satisfied
in a much more reasonable amount of time. The problem is that I can only
know how big the database. I could do a count and get an idea of how
large the database is and make a guess that the data is uniformly
distributed. There was a java command to restrict the number of records
saved setMaxSize(); but this does not seem to decrease the time of
execution of executeQuery(), and probably only uses less local memory.

If I have a statement like:

SELECT * FROM a;

and only want about the first 150 records, is there a way of speeding up
the query without doing a count(*) on a and doing something like this:

SELECT * FROM a WHERE '' <= a AND a < 'C';

--
Bob VonMoss
mailto:bvonmoss@bigfoot.com
from Chicago, IL

> I'm working with JDBC and if I issue a broad SELECT statement, with a
> good amount of records (2000) it takes quite a while to execute the
> query and send the results back, even up to a minute, when I only want
> about the first 100 records. If I restrict the search, it is satisfied
> in a much more reasonable amount of time. The problem is that I can only
> know how big the database. I could do a count and get an idea of how
> large the database is and make a guess that the data is uniformly
> distributed. There was a java command to restrict the number of records
> saved setMaxSize(); but this does not seem to decrease the time of
> execution of executeQuery(), and probably only uses less local memory.

have a look at using cursors.

worked for me.

--
[ Jim Mercer    Reptilian Research      jim@reptiles.org   +1 416 410-5633 ]
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