The persistence query language (QL) is one of the most important parts of the Java Persistence API. As the name suggest, the JPA QL is used to perform complex queries on database entities and to perform bulk update operations. The JPA QL seems very similar to SQL. Actually, it borrows the same syntax, with one key difference: the JPA QL uses an object-oriented approach rather than a relational approach.
To use JPA queries, you will have first to instantiate a query object that you can use to execute queries using the JPA QL. Let's see an examples:
Query query = entityManager.createQuery("SELECT m FROM Movie m");
List<Query> results = query.getResultList(); As you can see, we have used the createQuery method of the enitityManager object to create a query object. We have passed a String containing the query itself as a parameter to this method. For sure, this query retrieves a list of all the movie entities that exist in the database.
In the second line, we have invoked...