Urgent: Need information on Oracle

Question

Hello,
I have 10,000 records in Oracle Database. I need to fetch 1000 records at one time. Is it possible in Oracle. Can someone tell me how?

Answer 1

There are a few ways to do this, the two most common being caching the data in memory, and using ordered data to query agains.
Caching is pretty simple, especially with classes like CachedRowSet to play with. The entire data set is kept in memory and you have to keep track of pointers as you move back and forth through the rows. The larger your dataset, the less functional this approach.
Querying against ordered data allows you to use the rownum pseudocolumn. You start with a known value, get ordered data above/below that value, and use rownum to give you the number of rows you need. The rownum value is assigned before ordering, so you have to order in a subquery.   Statement stmt = conn.createStatement(ResultSet.CONCUR_READ_ONLY, ResultSet.TYPE_SCROLL_INSENSITIVE);
   String query = "select min(field) from schema.table"; //get the starting point
   ResultSet rs = stmt.executeQuery();
   if (!rs.next()) someErrorCondition();
   String startValue = rs.getString(1);
   rs.close();
   query = "select * from schema.table where field in " +
           "(select field from schema.table where field >= " +  
           startValue + ") and rownum <= 1000";
   rs = stmt.executeQuery(query);
   if (!rs.next()) someErrorCondition();
   rs.last();
   startValue = rs.getString(1);
   rs.first(); //loop through the data, etc.
   rs.close();
   //get the next page
   query = "select * from schema.table where field in " +
           "(select field from schema.table where field > " +
           startValue + ") and rownum <= 1000";
   rs = stmt.executeQuery(query);That's a quick look, anyway. A problem with this is the number of trips to the database to accomplish a single page pass; you'll either have to do a rs.last() to find the startValue for the next page, or loop through the entire contents of the page and keep track of the last value.
Oracle gives many reasons for not implementing an easier way to do this (mostly to do with data concurrency) but I think they could work it out if they tried.