Derby/SQL - How to increase performance when left joining and retrieving varchar columns
The lack of a WHERE clause or an ORDER BY clause probably means that your query is not using an index (and is most certainly selecting all rows in the table).

So, I'd suggest:


Add a "WHERE" clause
Add an "ORDER BY" clause
Make sure that you have appropriate indexes on the two tables for the ids and the columns in the WHERE and ORDER BY clauses. 
Look at the query execution plan to make sure that your indexes are used.