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Explanation

JPA Query is used to communicate with the database in Java applications using JPA (Java Persistence API). It helps to fetch, insert, update, and delete data.

Code:

@Repository
public interface UserRepository extends 
JpaRepository<User, Long> {

}

Explanation

Method Name Query automatically generates SQL queries based on the method name.

Code:

List<User> findByName(String name);

Explanation

JPQL Query uses entity class names and entity fields instead of database table names.

Code:

@Query("SELECT u FROM User u")
List<User> getAllUsers();

Explanation

Fetch a user using email with JPQL query.

Code:

@Query("SELECT u FROM User u WHERE 
u.email = :email")
User findByEmail(@Param("email") 
String email);

Explanation

Native Query uses actual SQL queries directly.

Code:

@Query(value = "SELECT * FROM users",
 nativeQuery = true)
List<User> getUsers();

Explanation

Insert operation is usually done using save() method provided by JpaRepository.

Code:

userRepository.save(user);

Explanation

Update query in JPA requires @Modifying and @Transactional annotations.

Code:

@Modifying
@Transactional
@Query("UPDATE User u SET u.name = :name 
WHERE u.id = :id")
void updateName(@Param("id") Long id, 
@Param("name") String name);

Explanation

Delete query removes records from the database using JPQL.

Code:

@Modifying
@Transactional
@Query("DELETE FROM User u WHERE u.id = :id")
void deleteUser(@Param("id") Long id);

Explanation

Sorting can be done using ORDER BY in JPQL query.

Code:

@Query("SELECT u FROM User u 
ORDER BY u.name ASC")
List<User> getUsersSorted();

Explanation

LIKE operator is used for searching records with partial matching.

Code:

@Query("SELECT u FROM User u WHERE u.name 
LIKE %:keyword%")
List<User> searchUsers(@Param("keyword") 
String keyword);