If you've used relational databases extensively, you might be tempted to perform all your JDO queries with SQL. Try to resist this temptation. SQL queries tie your application to the particulars of your current data model and database vendor. If you stick with JDOQL, on the other hand, you can port your application to other schemas and database vendors without any changes to your code. Additionally, most JDO implementations already produce highly optimized SQL from your JDOQL filters, and many are able to cache JDOQL query results for added performance.