I create 3 tables
articles : id title
category: id name
article_category: id article_id category_id main
And in Category
model:
public function articles()
{
return $this->belongsToMany(Article::class);
}
I want add data to article_category
:
$article_id = 20;
$category_id = 1;
$category = Category::find($category_id);
$cat[$article_id] = ['main'=>false];
$category ->articles()->sync($cat);
$article_id = 20;
$category_id = 2;
$category = Category::find($category_id);
$cat[$article_id] = ['main'=>false];
$category ->articles()->sync($cat);
Now In article_category
I have:
article_id category_id main
20 1 false
20 2 false
Ok It seems normal.
for example if add this again:
$article_id = 20;
$category_id = 2;
$category = Category::find($category_id);
$cat[$article_id] = ['main'=>false];
$category ->articles()->sync($cat);
It not generate duplication rows.
Now my problem is this:
If I add a new article_id, It remove all last saved records.
for example with add these codes:
$article_id = 21;
$category_id = 1;
$category = Category::find($category_id);
$cat[$article_id] = ['main'=>false];
$category ->articles()->sync($cat);
$article_id = 21;
$category_id = 2;
$category = Category::find($category_id);
$cat[$article_id] = ['main'=>false];
$category ->articles()->sync($cat);
I expect this:
article_id category_id main
20 1 false
20 2 false
21 1 false
21 2 false
But In my databse I have this:
article_id category_id main 21 1 false 21 2 false
what's my wrong?
As per the documentation in Laravel 5.6, Any IDs that are not in the given array will be removed from the intermediate table. It will only make many to many relation for category_id in which $cat variable contains its respective id.
This is why, it will remove all last saved records when adding a new article.
If you want to attach the new relationship, simply use
$category->articles()->syncWithoutDetaching($cat);