["slug" being an entity attribute] Spring Data offers an existsBy query method, which we can define in the PostRepository, as follows: 1 2 3 4 5 6

@Repository public interface PostRepository extends JpaRepository<Post, Long> {

boolean existsBySlug(String slug);

}

[another] option to emulate existence is using a CASE WHEN EXISTS native SQL query: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

@Repository public interface PostRepository extends JpaRepository<Post, Long> {

@Query(value = """
    SELECT
        CASE WHEN EXISTS (
            SELECT 1
            FROM post
            WHERE slug = :slug
        )
        THEN 'true'
        ELSE 'false'
        END
    """,
    nativeQuery = true
)
boolean existsBySlugWithCase(@Param("slug") String slug);

}