MySQL Join，即使不匹配…Laravel

Question

Here is my Laravel query:

$all_tags = DB::table('tags')
        ->join('products', 'tags.product_id', '=', 'products.id')
        ->leftJoin('resources', 'tags.resource_id', '=', 'resources.id')
        ->where('tags.user_id', $user_id)
        ->select('tags.id as tag_id', 'tags.serial_number', 'tags.pin_number', 'tags.expiry_date', 'tags.active as tag_active', 'tags.activation_date', 'products.name', 'products.image', 'resources.name as resource_name')
        ->get();

The problem is, sometimes there is no matching product and sometimes there is no matching resource ...

How do I deal with the "select" statement in this case?

Answer 1

如果即使在没有匹配的产品且没有匹配的资源的情况下也要返回标签，则需要在产品和资源表上都使用左连接。