JPQL (Java/Jakarta Persistence Query Language)

• Avoiding SQL inside Java logic.
• Object-oriented query language for JPA.
• Works with entities and their fields, not database tables/columns.
• Portable across databases.
• Converted to SQL by JPA/Hibernate before executing in the database.

Rules for creating JPQL

1. select all

   SQL : SELECT * FROM USER
   JPQL: SELECT u FROM User u 
   

2. select specific field

   SQL : SELECT id,name FROM USER
   JPQL: SELECT u.id ,u.name FROM User
   

Here(JPQL perspective)

User = Entity class name (not table name). id, name = Entity property names (not column names).

Example

Repository

public interface UserRepository extends JpaRepository<User, Integer> {
    @Query(value = "SELECT u FROM User u ", nativeQuery = false)
    List<User> getUserJpql();
}

Method

 public void getUserJpqlMethod() {
     List<User> users = userRepository.getUserJpql();
      users.forEach(u -> {
      System.out.println(u.getId() + " " + u.getName() + " " + u.getEmail());
     });
 }

SQL

JPQL: SELECT u FROM User u 
SQL : SELECT * FROM USER
Hibernate: select u1_0.uid,u1_0.email,u1_0.name from user u1_0

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Github Code : CRUD Operation