Java: What is the difference between JPQL and SQL?

JPQL — queries entities. SQL — queries tables.

JPQL:

• Uses entity names and field names.
• Database-independent.
• No JOIN syntax (uses relationships).
• Returns entities or projections.
• Part of JPA specification.

1@Query("SELECT u FROM User u WHERE u.name LIKE %:name%")
2List<User> searchByName(@Param("name") String name);
3
4@Query("SELECT u.name FROM User u WHERE u.age > :age")
5List<String> findNamesByAge(@Param("age") int age);

SQL:

• Uses table names and column names.
• Database-specific.
• Full JOIN syntax.
• Returns raw data.
• More powerful for complex queries.

1SELECT * FROM users WHERE name LIKE '%Alice%'
2SELECT u.name FROM users u JOIN orders o ON u.id = o.user_id

How it works:

1. JPQL is translated to SQL by the JPA provider.
2. JPQL uses entity and field names, not table and column names.
3. JPQL is portable across databases.
4. SQL is database-specific.

Key difference:

• JPQL — entity-level, portable.
• SQL — table-level, database-specific.

Best practice:

• Use JPQL for portability.
• Use SQL for complex queries or performance optimization.
• Use native queries when JPQL is insufficient.