Hibernate: A Developer's Notebook

9.1. Writing HQL Queries

We've already shown that you can get by with fewer pieces in an HQL query than you might be used to in SQL (the queries we've been using, such as those in Chapter 3, have generally omitted the "select" clause). In fact, the only thing you really need to specify is the class in which you're interested. Example 9-1 shows a minimal query that's a perfectly valid way to get a list of all Track instances persisted in the database.

HQL stands for Hibernate Query Language. And SQL? It depends who you ask.

Example 9-1. The simplest HQL query

from Track

There's not much to it, is there? This is the HQL equivalent of Example 8-1, in which we built a criteria query on the Track class and supplied no criteria.

By default, Hibernate automatically "imports" the names of each class you map, which means you don't have to provide a fully qualified package name when you want to use it, the simple class name is enough. As long as you've not mapped more than one class with the same name, you don't need to use fully qualified class names in your queries. You are certainly free to do so if you prefer–as I have in this book to help readers remember that the queries are expressed in terms of Java data beans and their properties, not database tables and columns (like you'd find in SQL). Example 9-2 produces precisely the same result as our first query.

Example 9-2. Explicit package naming, but still pretty simple

from com.oreilly.hh.Track

If you do have more than one mapped class ...