Java: What is the difference between @Query and @Modifying?

@Query — defines JPQL/SQL query. @Modifying — enables update/delete operations.

@Query:

• Defines SELECT queries.
• Returns entities or projections.
• Read-only.
• Supports JPQL and native SQL.

1@Query("SELECT u FROM User u WHERE u.name = :name")
2List<User> findByName(@Param("name") String name);
3
4@Query("SELECT u.name, u.email FROM User u WHERE u.age > :age")
5List<Object[]> findNameEmailByAge(@Param("age") int age);

@Modifying:

• Enables UPDATE/DELETE queries.
• Requires @Transactional.
• Clears persistence context.
• Returns affected row count.

1@Modifying
2@Transactional
3@Query("UPDATE User u SET u.active = false WHERE u.lastLogin < :date")
4int deactivateUsers(@Param("date") LocalDate date);
5
6@Modifying
7@Transactional
8@Query("DELETE FROM User u WHERE u.active = false")
9int deleteInactiveUsers();

How it works:

1. @Query defines the query to be executed.
2. @Modifying enables write operations (UPDATE/DELETE).
3. @Modifying requires @Transactional for data consistency.
4. @Modifying clears the persistence context after execution.

Key difference:

• @Query — SELECT.
• @Modifying — UPDATE/DELETE.

Best practice:

• Use @Modifying for bulk updates/deletes.
• Always use @Transactional with @Modifying.
• Consider the impact on cached entities.