Retrieve a general rating and display in a list

Question

Good evening guys, I’m in the following situation,

I have a table called cars, and each car can be evaluated by different users, so far so good, I created a secondary table called reviews and each car can be evaluated by several different users.

Now I need each car to show a general review, which and pick up all reviews from all users on a particular car and show in a list with all cars.

Oh that my doubt, how to recover all evaluations of the evaluation table.

I entered the table to better understand, I will only take the sum of the general evaluation and how many people evaluated the same car example

GOLF - 2 reviews - 7 points

$sql = $conex->query("SELECT * FROM carros");
while($rs=$conex->result($sql)){
                    $id_car=$rs['id_car'];
                    $nome_car=$rs['nome_car'];
};

// Table ----------------------------------------------------------------

CREATE TABLE IF NOT EXISTS `avaliacao` (
  `id_ava` int(11) NOT NULL,
  `id_car_ava` int(11) NOT NULL,
  `id_usu_ava` int(11) NOT NULL,
  `dirigibilidade_ava` int(11) NOT NULL,
  `estabilidade_ava` int(11) NOT NULL,
  `potencia_ava` int(11) NOT NULL,
  `consumo_ava` int(11) NOT NULL,
  `geral_ava` int(11) NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

--
-- Extraindo dados da tabela `avaliacao`
--

INSERT INTO `avaliacao` (`id_ava`, `id_car_ava`, `id_usu_ava`, `dirigibilidade_ava`, `estabilidade_ava`, `potencia_ava`, `consumo_ava`, `geral_ava`) VALUES
(1, 1, 2, 4, 2, 2, 4, 4),
(2, 1, 6, 4, 4, 5, 5, 5),
(3, 2, 7, 5, 5, 5, 4, 3),
(4, 3, 9, 4, 4, 4, 4, 3);

-- --------------------------------------------------------

--
-- Estrutura da tabela `carros`
--

CREATE TABLE IF NOT EXISTS `carros` (
  `id_car` int(11) NOT NULL,
  `model_car` varchar(200) NOT NULL,
  `ano_car` int(12) NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

--
-- Extraindo dados da tabela `carros`
--

INSERT INTO `carros` (`id_car`, `model_car`, `ano_car`) VALUES
(1, 'Golf', 2000),
(2, 'Pálo', 1998),
(3, 'Jeta', 2015),
(4, 'Peugeout 206', 2006);

--
-- Indexes for dumped tables
--

--
-- Indexes for table `avaliacao`
--
ALTER TABLE `avaliacao`
  ADD PRIMARY KEY (`id_ava`);

--
-- Indexes for table `carros`
--
ALTER TABLE `carros`
  ADD PRIMARY KEY (`id_car`);

--
-- AUTO_INCREMENT for dumped tables
--

--
-- AUTO_INCREMENT for table `avaliacao`
--
ALTER TABLE `avaliacao`
  MODIFY `id_ava` int(11) NOT NULL AUTO_INCREMENT,AUTO_INCREMENT=5;
--
-- AUTO_INCREMENT for table `carros`
--
ALTER TABLE `carros`
  MODIFY `id_car` int(11) NOT NULL AUTO_INCREMENT,AUTO_INCREMENT=5;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

Answer 1

The SQL you want

SELECT *, (SELECT COUNT(*) FROM avaliacao WHERE id_car_ava=id_car) AS QT FROM carros

Example.:
http://sqlfiddle.com/#! 9/23cfaf/2