The Jakarta Persistence Query Language (JPQL; formerly Java Persistence Query Language) is a platform-independent
object-oriented
Object-oriented programming (OOP) is a programming paradigm based on the concept of '' objects''. Objects can contain data (called fields, attributes or properties) and have actions they can perform (called procedures or methods and impleme ...
query language
A query language, also known as data query language or database query language (DQL), is a computer language used to make queries in databases and information systems. In database systems, query languages rely on strict theory to retrieve informa ...
defined as part of the
Jakarta Persistence (JPA; formerly Java Persistence API) specification.
JPQL is used to make queries against entities stored in a relational database. It is heavily inspired by
SQL
Structured Query Language (SQL) (pronounced ''S-Q-L''; or alternatively as "sequel")
is a domain-specific language used to manage data, especially in a relational database management system (RDBMS). It is particularly useful in handling s ...
, and its queries resemble SQL queries in syntax, but operate against JPA entity objects rather than directly with database tables.
In addition to retrieving objects (
SELECT queries), JPQL supports set based
UPDATE and
DELETE queries.
Examples
Example JPA Classes, getters and setters omitted for simplicity.
@Entity
public class Author
@Entity
public class Book
@Entity
public class Publisher
Then a simple query to retrieve the list of all authors, ordered alphabetically, would be:
SELECT a FROM Author a ORDER BY a.firstName, a.lastName
To retrieve the list of authors that have ever been published by XYZ Press:
SELECT DISTINCT a FROM Author a INNER JOIN a.books b WHERE b.publisher.name = 'XYZ Press'
JPQL supports named parameters, which begin with the colon (
:). We could write a function returning a list of authors with the given last name as follows:
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
...
public List getAuthorsByLastName(String lastName)
Hibernate Query Language
JPQL is based on the
Hibernate Query Language (HQL), an earlier non-standard query language included in the
Hibernate
Hibernation is a state of minimal activity and metabolic reduction entered by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It is most ...
object-relational mapping library.
Hibernate and the HQL were created before the JPA specification.
As of Hibernate 3 JPQL is a subset of HQL.
Citations
References
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See also
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Object-relational mapping
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Hibernate (framework)
Hibernate ORM (or simply Hibernate) is an object–relational mapping tool for the Java programming language. It provides a framework for mapping an object-oriented domain model to a relational database. Hibernate handles object–relational ...
*
Jakarta Persistence
External links
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Full Query Language Syntax from The Jakarta EE 8 TutorialJPA Queries and JPQL - a chapter of the ObjectDB ManualType safe Hibernate (HQL) query engine - TorpedoQuery
{{Jakarta Persistence
Query languages
Data modeling languages
Java enterprise platform