Best way to limit results from a query.

Question

I need to limit the number of results returned from the database to the first x rows. What I need is a database independant way to achieve this - i.e. I can't use LIMIT, TOP, etc. in my query.
My question therefore is does statment.setMaxRows(x) restrict my results at the database level or my application's view to the database? I.e. will the complete SELECT * run within the database but the first x will be returned to the resultset, which could be quite a performance drain at db level. Or will this have the same effect as running a query SELECT TOP X FROM... which will be a much quicker query to run?
Any help greatly appreciated!

Answer 1

The best, and only fool proof way to limit results (rows, columns) from a query, and not waste database resources is to code your query so it only returns the rows and columns that you need. That might mean providing date ranges, sequence number ranges and all other WHERE criteria that can be used to filter the data to exactly what you need.
There are ways to limit what is available to your Java program, but in most cases, the entire SQL must be completed before any results can be returned. The simplest example is; using the SORT command to get the data into the order you require, will first require that all rows be made available to the sort. The fact that you only want the top 5 rows doesn't matter to the DBMS because it cannot give them to you incrementally.
Focus on getting your SQL as efficient as possible. If the SQL runs efficiently, you can use almost any of the JDBC commands to limit, list, cursor forward and backward, etc, without regard to their overhead.