Retrieving single value using JPA?

Question

Is there any support by JPA to map single values to scalar data types? For example, to map NUM in the following query

SELECT COUNT(*) AS NUM FROM EMPLOYEES

to some variable

int numerOfEmployees

or do I have to use JDBC for such use cases?

Answer 1

Yes, you can return scalar types from JPQL queries

long num = ((Number)em.createQuery("select count(e) from Employee e")
                    .getSingleResult()).longValue();

as well as from native SQL queries:

long num = ((Number)em.createNativeQuery("select count(*) from Employees")
                    .getSingleResult()).longValue();

Note that in some cases result type may depend on the database, i.e. it can be something like BigDecimal.