Laravel whereHas manyToMany exact match - php

Question

I have a Model with manyToMany relationship:
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class Product extends Model
{
public function categories()
{
return $this->belongsToMany(Category::class, 'product_category', 'product_id', 'category_id');
}
}
So 1 Product can have multiple Categories.
I'm trying to query (fetch) all Products that have exact match of categories:
Example:
$categories = ['category1', 'category2'];
Product::whereHas('categories', function($q) use ($categories){
foreach ($categories as $categoryName) {
$q->where('name', $categoryName);
}
//or $q->whereIn('name', $categories);
})->get();
Also tried:
$categories = ['category1', 'category2'];
Product::whereHas('categories', function($q) use ($categories){
$q->whereIn('name', $categories);
}, '=', count($categories))->get();
Assume my Product has only category1 attached, the query should return this product.
If Product has both categories, but my array contains only category1, then this Product should be ignored.
So I'm trying to achieve: Fetch only products with specific categories. It is doable with Eloquent or DB builder?
Pseudo Code
$allow = for each Product->categories{
category Exist in $categories
}

Answer 1

Based on your requirement your MySQL query would be as follow:
Use LEFT JOIN to get total numbers of mapped categories for a product.
Use GROUP BY on a product to compare its total mapped categories vs matching categories based on user input.
Above comparison can be done using HAVING clause, where total mapped categories should be equal to the count of categories the user has provided. Same matching categories based on user input should also match the exact count of categories which the user has provided.
SELECT p.id
FROM products p
LEFT JOIN product_category pc ON p.id = pc.product_id
LEFT JOIN categories c ON c.id = pc.category_id AND c.name IN ('category1', 'category2')
GROUP BY p.id
HAVING COUNT(0) = 2 -- To match that product should have only two categories
AND SUM(IF(c.name IN ('category1', 'category2'), 1, 0)) = 2; -- To match that product have only those two categories which user has provided.
Same can be achieved by query builder in the following manner:
$arrCategory = ['category1', 'category2'];
$strCategory = "'" . implode("','", $arrCategory) . "'";
$intLength = count($arrCategory);
$products = Product::leftJOin('product_category', 'products.id', '=', 'product_category.product_id')
->leftJoin('categories', function ($join) use ($arrCategory) {
$join->on('categories.id', '=', 'product_category.category_id')
->whereIn('categories.name', $arrCategory);
})
->groupBy('products.id')
->havingRaw("COUNT(0) = $intLength AND SUM(IF(categories.name IN ($strCategory), 1, 0)) = $intLength")
->select(['products.id'])
->get();
dd($products);
Note: If you have only_full_group_by mode enabled in MySQL, then include columns of products table in both group by and select clause which you want to fetch.

Answer 2

Try using this without wherehas
Product::with(array('categories' => function($q) use ($categories){
$query->whereIn('name', $categories);
}))->get();

Answer 3

Thank you for your answers I solved this with: whereExists of sub select fromSub and array_agg, operator <# (is contained by):
$categories = ['category1', 'category2'];
Product::whereExists(function ($q) use ($categories){
$q->fromSub(function ($query) {
$query->selectRaw("array_agg(categories.name) as categoriesArr")
->from('categories')
->join('product_category', 'categories.id', '=', 'product_category.category_id')
->whereRaw('products.id = product_category.product_id');
}, 'foo')->whereRaw("categoriesArr <# string_to_array(?, ',')::varchar[]", [
implode(",", $categories)
]);
})->get();