jpa mysql分组查询语句

@Entity
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private String customerId;
    
    private BigDecimal amount;
    
    // getters and setters
}

@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
    @Query("SELECT o.customerId, SUM(o.amount) FROM Order o GROUP BY o.customerId")
    List<Object[]> findTotalAmountByCustomerId();
}

public class CustomerOrderSummary {
    private String customerId;
    private BigDecimal totalAmount;
    
    public CustomerOrderSummary(String customerId, BigDecimal totalAmount) {
        this.customerId = customerId;
        this.totalAmount = totalAmount;
    }
    
    // getters
}

@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
    @Query("SELECT new com.example.CustomerOrderSummary(o.customerId, SUM(o.amount)) FROM Order o GROUP BY o.customerId")
    List<CustomerOrderSummary> findCustomerOrderSummary();
}