Named and Native Queries in JPA

Named  and Native Queries in JPA :-

• Named queires are reusable and can be declared at Entity level
• @NamedQuery annotation is used
• multiple named queries are declared in @NamedQueries
• For executing native queries we use @NamedNativeQueries

@NamedQuery :-

@NamedQuery(name = "allCompanyDetails", query = "SELECT c FROM Company c")

Named query is called by using query = em.createNamedQuery("allCompanyDetails");

@NamedQueries :- annotation is used for declaring multiple named queries at entity level

In the below snippet we have two named queries-"allCompanyDetails" and "onlyMailIds"

@NamedQueries({ @NamedQuery(name = "allCompanyDetails", query = "SELECT c FROM Company c"),

@NamedQuery(name="onlyMailIds",query="SELECT c.mail FROM Company c")

})

Native Queries are used to execute SQL statements directly and to call procedures and functions from JPA

@NamedNativeQueries :-

@NamedNativeQuery(name = "nativeQueryEx", query = "select * from company")

entityManager.createNativeQuery("query") is used to execute native queries

Similar to SQL in JPQL we can write join queries etc,instead of Table names we use Entity class names

Query query = em.createQuery("SELECT c from Company c,Department d where c.mail= d.mail and c.name LIKE 'T%'");

Adding queries is easier if we use JPA details view in eclipse