How can I use mysql null safe equality operator <=> in HQL? - mysql

Question

I wanted to get records of Patient(POJO class) who's contact number is not null. So, I referred this post.
In the answer two ways are specified
SELECT *
FROM table
WHERE YourColumn IS NOT NULL;
SELECT *
FROM table
WHERE NOT (YourColumn <=> NULL);
From above I wrote below hql which runs successfully
from Patient p where p.contactNo is not null
But, for 2nd type of hql
from Patient p where not (p.contactNo <=> null)
throws Exception
org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: >
How can I use mysql null safe equality operator <=> in HQL?

Answer 1

HQL is a different language than MySQL. MySQL operators are not necessarily available in HQL.
This being said, you can given Hibernate MySQL queries (provided your database is MySQL):
Query query = entityMangager.createNativeQuery("Some MySQL code");
List results = query.getResultList();
EntityManager is an interface from the Java Persistence API. Hibernate has a tutorial about using the JPA, but here are the main points:
In order to have an entity manager, you need META-INF/persistence.xml file in your classpath. Then, inside a Java EE container, you get an instance of this interface with the #PersistenceContext annotation:
#PersistenceContext(unitName = "persistenceUnit")
private EntityManager em;
Outside a Java EE container, you can get one with the Persistence class:
EntityManagerFactory factory = Persistence.createEntityManagerFactory("persistenceUnit");
EntityManager em = factory.createEntityManager();
In both case, "persistenceUnit" must be the name of a persistence unit defined in your persistence.xml file.