Count quantity of books by category, separate tables - mysql

Question

I'm using Laravel 5 and I need to know the number of books by category, these data I will use on google charts.
I have the code below that I use to find out the number of users by sex. However, the data is in the same table.
$data = DB::table('books')
->select(
DB::raw('category_id as category'),
DB::raw('count(*) as number'))
->groupBy('category')
->get();
$array[] = ['Category', 'Number'];
foreach($data as $key => $value)
{
$array[++$key] = [$value->category->name, $value->number];
}
$test = json_encode($array);
Using the same logic as above, how can I get the number of books by category?
I have the Books table:
ID | Name | ID_CATEGORY
1 Laravel 20
2 Java 20
Category table :
ID | Name
20 Programming
Could you help me in this situation?

Answer 1

You should just group by your ID_CATEGORY column instead of sex.
If you want to construct such array as before, you probably want the name of category. That would be easy if you used Eloquent. You would have $value->category->Name_Category available. If you want those preloaded instead of a query for every value, just add ->with('category') to the query and you'll have it.
If you are not using Eloquent, you should just load the category table separately, key it, and use $categories[$value->ID_CATEGORY]->Name_Category.
Other comments
DB::raw('sex as sex') is equivalent to sex.
++$key seems redundant, you could just push to the end by assigning to $array[].
Array with a header row is not very JSON. Typically you'd have key:value pairs all of the time.
You can construct the array using collection methods.
If you don't have good reasons for the opposite, you should stick to Laravel naming conventions.
I would probably not create an array myself, but do your example as something like this:
$stats = User::select('sex', DB::raw('count(*) as number'))
->groupBy('sex')
->get();
$stats->setVisible(['sex', 'number']);
return $stats;