Foreach in a while loop - mysql

Question

I’ve two tables: “cars” and “dealerships”:
Cars table
id_car | name_car | etc.
----------------------------
1 | A3 Sportback | etc.
2 | Ranger | etc.
3 | Transit Van |etc.
4 | Cayman | etc.
etc. | etc. | etc.
Dealerships table
In deal_cars column I insert ids of correspondent cars as array.
deal_id | deal_name | deal_cars | etc.
--------------------------------------
1 | Ford | 2,3 | etc.
2 | Audi | 1 | etc.
3 | Porsche | 4 | etc.
etc. | etc. | etc. |
I’d get a page that displays the following information:
Dealership name – Cars
Ford – Ranger, Transit Van
Audi – A3 Sportback
Cayman – Porsche
I’ve no problem to extract the dealership name, but I don’t know how to extract the car names from ids.
I tried this:
$dealerships_sql = $data->query("SELECT * FROM dealerships ORDER BY deal_name ASC");
while($dealerships_obj = $data->extract($dealerships_sql)){
//Dealerships data
$deal_id[] = $dealerships_obj->deal_id;
$deal_name[] = $dealerships_obj->deal_name;
etc etc
//Try to get cars ids and turn them in cars names.
$deal_cars[] = $dealerships_obj->deal_cars;
$deal_cars[] = explode(',',$deal_cars);
$cars = array();
foreach ($deal_cars AS $deal_car) {
$cars_sql = $data->query("SELECT name_car FROM cars WHERE id_car = '$deal_car'");
while($cars_obj = $data->extract($cars_sql)){
$cars[] = stripslashes($cars_obj->name_car)." ";
}
}
}
I use smarty as template engine so I assign some vars:
$smarty->assign ("deal_id", $deal_id);
$smarty->assign ("deal_name", $deal_name);
etc etc.
$smarty->assign ("cars", $cars);
And my template is:
<table border="1">
<tr>
<td>Dealership</td>
<td>Cars</td>
</tr>
{section name="foo" loop=$deal_name}
<tr>
<td>{$deal_name[foo]}</td>
<td>{$cars[foo]}</td>
</tr>
{/section}
</table>
But code returns:
Ford – Ranger
Audi – A3 Sportback
Cayman – Porsche
It shows only the first car (first element found in array) for each dealership. How can I solve this?

Answer 1

I think your database design does not fit right here.
Cars Table
id_car | name_car | etc.
----------------------------
1 | A3 Sportback | etc.
2 | Ranger | etc.
3 | Transit Van | etc.
4 | Cayman | etc.
etc. | etc. | etc.
Dealer Table
deal_id | deal_name | etc.
---------------------------
1 | Ford | etc.
2 | Audi | etc.
3 | Porsche | etc.
etc. | etc. |
Dealer to Cars Table
dealerid | carid
1 | 2
1 | 3
2 | 1
etc. | etc.
As you see, I did another table for the relationships between the two tables.
$dealerships_sql = $data->query("SELECT * FROM dealerships ORDER BY deal_name ASC");
$dealers = array();
while($dealerships_obj = $data->extract($dealerships_sql)){
//Dealerships data, use object
$dealerid = $dealerships_obj->deal_id;
$dealers[$dealerid]['dealer'] = $dealerships_obj;
// Cars
$cars = array();
$car_sql = $data->query("SELECT name_car FROM cars JOIN dealerToCars ON carid = id_car JOIN dealer ON deal_id = dealerid WHERE deal_id = " . $dealerid);
// now you have all cars from the selected dealer
while ($cars_obj = $data->extract($car_sql))
{
$cars[] = stripslashes($cars_obj->name_car);
}
// Assign Cars to dealer
$dealers[$dealerid]['cars'] = $cars;
}
Now you have in $dealers all your dealers with their cars.
Since you are using smarty, just pass this whole array to smarty and let the rest do smarty in it's template. Smarty is able to use arrays and objects, so you don't need to split it into multiple arrays:
$smarty->assign ("dealers", $dealer);
Because I don't know your classes, you maybe need to add some getters or setters or just make the properties public, so smarty can access them:
<table border="1">
<tr>
<td>Dealership</td>
<td>Cars</td>
</tr>
{foreach $dealers as $dealer}
<tr>
<td>{$dealer['dealer']->deal_name}</td>
<td>{foreach $dealer['cars'] as $car}{$car}, {/foreach}</td>
</tr>
{/foreach}
</table>
Maybe you need to take a look about the identifiers in the template.
(I'm using smarty 3 for that)

Answer 2

I think you should have a dealership row for each car (that will allow you to get all the information with a JOIN and parse it all easily).

Answer 3

The best way would be to get everything at once, you can do it like that:
select
d.deal_name,
group_concat(c.name_car order by c.name_car separator ', ')
from dealerships d
join cars c on find_in_set(c.id_car, d.deal_cars) > 0
group by d.deal_name;
or (as separated fields):
select d.deal_id, d.deal_name, c.id_car, c.name_car
from dealerships d
join cars c on find_in_set(c.id_car, d.deal_cars) > 0;