Result set limits

Hi,
I'm new to postgreSQL and was wondering if there is a way to return only
a set of rows back to the user at a time? Does it need to be explicitly
Stated in the query? Or is it something that the jdbc driver takes care
of for you?
So an example:
Let's say that I want to return 50 rows at a time should there be more
than 50 returns from the query. How would I do the following?
1.) Check the number or rows being returned without having to pull the
entire set down... this would defeat the efficiency issue I'm looking to
avoid
2.) return 50 at a time from the last set that was returned...
Clarification: The set of 50 is an arbitrary number picked to represent
a size. This size in reality may be set by the user.
Any help with this would be greatly appreciated. Thanks in advance

My apologies for the misleading subject line. Should be corrected now.

Damian Tamayo
General Dynamics C4 Systems
Student Intern
BMSD
Collaborative Battle Management Systems Section
480-441-1346

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