Intermittent results...has JOIN limit in PHP?

Question

I choose the car maker, the model, engine and year and perform the consultation so:

	$query = "SELECT b.montadora, m.modelo, n.motor, a.ano, d.descricao, c.combustivel, f.f_cabine, g.local_ar_cabine, h.f_ar, j.f_lub_princ, k.f_lub_opcional, l.f_combustivel FROM 13_tecfil t
				JOIN 0_montadora b
				ON t.montadora = b.id
					JOIN 1_modelo m
					ON t.modelo = m.id
						JOIN 2_motor n
						ON t.motor = n.id
							JOIN 3_ano a
							ON t.ano = a.id
								JOIN 4_descricao d
								ON t.descricao = d.id
									JOIN 5_combustivel c
									ON t.combustivel = c.id
										JOIN 6_f_cabine f
										ON t.f_cabine = f.id
											JOIN 7_local_ar_cabine g
											ON t.local_ar_cabine = g.id
												JOIN 8_f_ar h
												ON t.f_ar = h.id
													JOIN 9_f_lub_princ j
													ON t.f_lub_princ = j.id
														JOIN 10_f_lub_opcional k
														ON t.f_lub_opcional = k.id
															JOIN 11_f_combustivel l
															ON t.f_combustivel = l.id
																WHERE t.montadora = '". $_POST['id_montadora'] ."' AND
																t.modelo = '". $_POST['id_modelo'] ."' AND
																t.motor = '". $_POST['id_motor'] ."' AND
																t.ano = '". $_POST['id_ano'] ."'
																ORDER BY b.montadora";
	$result_query = mysqli_query($conn, $query);

However, there are cars that query returns data and have cars that returns NULL. The case is that if I reduce the query to just appear the indexes so:

	$query = "SELECT * FROM 13_tecfil
				WHERE montadora = '". $_POST['id_montadora'] ."' AND
				modelo = '". $_POST['id_modelo'] ."' AND
				motor = '". $_POST['id_motor'] ."' AND
				ano = '". $_POST['id_ano'] ."'
				ORDER BY montadora";
	$result_query = mysqli_query($conn, $query);

The cars that before returned nothing, returns data now, despite being only indexes. Is there any JOIN restriction in PHP? How can I make the first query work?

Answer 1

For Mysql there is a limit of 61 tables or 4096 columns.

In your case you would need a bank dump to evaluate relationships. Probably some foreign key there might not be hitting.

The 13_tecfil "id" column is present in all tables?

If it is the case that it is optional in any of them, try one FULL OUTER JOIN

https://stackoverflow.com/questions/4796872/how-to-do-a-full-outer-join-in-mysql

Answer 2

Well...I was able to find the problem. Some tables my primary keys could be blank, theoretically. The problem is that the value was NULL It was a problem. I decided to change these empty values to a foreign key "-" and voila...