We can have queries saved with a name and later we can retrieve them simply using that name. We use @NamedQuery annotation to declare a named query. We can also have a named query for native sql. For native SQL we use the annotation @NamedNativeQuery annotation. This is one of the important advantages of having a named query: you can write native SQL. You can retrieve a Query object from a saved query name (hql and native named query) using session.getNamedQuery method.

Parameter binding is the process of binding a Java variable with an HQL statement. Using Parameter binding and not string concatenation for HQL statement creation will also guard against attacks like SQL injection.

Hibernate provides a query language called Hibernate Query Language (HQL). HQL is similar to SQL in syntax, but HQL queries are written against Hibernate's entity objects, not database tables. Hibernate also provide Criteria Queries as an object-oriented alternative to HQL. Criteria Query is used to modify the objects and provide the restriction for the objects. Here we will see the basics of HQL and later in another tutorial we will see criteria queries.

Hibernate uses following strategies for saving an inheritance hierarchy of classes created in Java to the databases: SINGLE_TABLE, TABLE_PER_CLASS and JOINED.  

We can use @Inheritance annotation over the entity class to specify the inheritance strategy.

We specify the inheritance strategy by assigning a strategy from the InheritanceType enumeration to the strategy parameter of the @Inheritance annotation.  

In the JOINED strategy, hibernate will create a separate table for all the classes in an inheritance hierarchy, and the tables are normalized. Columns that you receive as part of inheritance will be part of parent class and referred from subclass tables using a foreign key. 

In this example, we will create and save three entity classes – Shape, Rectangle and Circle; where Rectangle and Circle extends from Shape.