What is Spring Data JPA query methods and JPQL?

Spring Data JPA provides multiple ways to define data access queries: 1. Derived query methods (from method name): Spring Data parses the method name and generates the JPQL query: List<User> findByLastNameAndFirstName(String lastName, String firstName); List<User> findByAgeBetween(int min, int max); List<User> findByEmailContainingIgnoreCase(String keyword); List<User> findTop5ByOrderByCreatedAtDesc(); Optional<User> findFirstByEmailOrderByIdDesc(String email); boolean existsByEmail(String email); long countByStatus(String status);. Keywords: findBy, readBy, getBy, countBy, existsBy, deleteBy, And, Or, Not, Like, Containing, StartingWith, EndingWith, Between, LessThan, GreaterThan, OrderBy, Top, First. 2. @Query with JPQL: JPQL uses entity class names and field names (not table/column): @Query("SELECT u FROM User u WHERE u.email = :email AND u.status = :status") Optional<User> findActiveByEmail(@Param("email") String email, @Param("status") String status); @Query("SELECT u FROM User u WHERE SIZE(u.orders) > :minOrders") List<User> findUsersWithManyOrders(@Param("minOrders") int min);. 3. @Query with native SQL: @Query(value = "SELECT * FROM users WHERE full_text_search(?) > 0", nativeQuery = true) List<User> searchUsers(String term);. 4. @Modifying: for UPDATE/DELETE queries: @Modifying @Transactional @Query("UPDATE User u SET u.lastLogin = CURRENT_TIMESTAMP WHERE u.id = :id") int updateLastLogin(@Param("id") Long id);. 5. Projections: return partial data as interface or DTO: interface UserNameEmail { String getName(); String getEmail(); } List<UserNameEmail> findByStatus(String status);. 6. Specification: dynamic queries with Criteria API.