laravel query cancel one to many

Laravel is one of the more popular open source PHP web application frameworks. Due to its ease of use, efficiency and flexibility, more and more developers use Laravel to create high-quality web applications.

In Laravel, we often encounter one-to-many data relationships, that is, the relationship between a master table and multiple slave tables. This relationship can be achieved through foreign keys in the database. In Laravel, we can use Eloquent ORM (Object-Relational Mapping) to easily perform one-to-many data query operations. This article mainly introduces how to query and cancel one-to-many data relationships in Laravel.

1. Query one-to-many data relationships

In Laravel, we can use Eloquent ORM to query one-to-many data relationships. First we need to define the corresponding models and relationships. For example, we have a "users" table and an "orders" table. Each user can have multiple orders. We can define an orders() method in the user model to represent this. One-to-many relationship:

class User extends Model
{
    /**
     * 获取与用户相关联的所有订单。
     */
    public function orders()
    {
        return $this->hasMany('AppOrder');
    }
}

In the above code, we use the hasMany() method to define all orders associated with the user. This method receives two parameters. The first parameter is the slave model. name, the second parameter is the name of the foreign key (by default, the foreign key name is the name of the dependent model plus _id). Next, we can use the orders() method as follows to query all orders associated with the user:

$user = User::find(1);

// 获取与用户相关联的所有订单
$orders = $user->orders;

In the above code, we first use the find() method to find the order with ID 1 user object and then use $user->orders to get all orders associated with that user.

If we need to further filter orders, we can use the query builder to filter the query, for example:

// 获取与用户相关联的价格超过10元的订单
$orders = $user->orders()->where('price', '>', 10)->get();

In the above code, we use the where() method to filter the price of the order Orders over 10 yuan.

2. Cancel the one-to-many data relationship

Sometimes, in Laravel, we need to cancel the one-to-many relationship between a master table and a slave table. For example, we can subordinate an order to a user and make it unassociated.

In Laravel, we can cancel the relationship between a record and its dependent model by setting the foreign key to null. For example, if we want to subordinate the order with ID 1 to the user with ID 2, we can do it as follows:

$order = Order::find(1);

// 取消该订单与之关联的用户
$order->user_id = null;
$order->save();

In the above code, we first use the find() method to find the ID of 1's order object, then set the order's user_id attribute to null, and finally use the save() method to save the changes.

If we need to cancel the relationship between a user and all its associated orders, we can do it as follows:

$user = User::find(1);

// 取消该用户与相关联订单之间的关系
$user->orders()->update(['user_id' => null]);

In the above code, we first use the find() method To find the user object with ID 1, then use the orders() method to get all the orders associated with the user, and then use the update() method to set the user_id attribute of all orders to null.

3. Summary

In Laravel, we can use Eloquent ORM to easily perform one-to-many data query operations. Usually we can implement one-to-many data relationships by defining corresponding models and relationships, and we can use the query builder to further filter the data when querying. At the same time, we can also cancel the one-to-many relationship between a master table and a slave table, usually by setting the foreign key to null. When writing Laravel applications, we should make full use of the capabilities of Eloquent ORM to improve our development efficiency and the quality of written code.

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