Detailed analysis of Laravel Model model association

This article brings you relevant knowledge about laravel, which mainly introduces related issues about Model model association, including one-to-one, one-to-many, many-to-many, etc. , let’s take a look at it, I hope it will be helpful to everyone.

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Define association relationships

Database tables are usually related to each other.
For example, a blog post may have many comments, or an order may correspond to one ordering user. Eloquent makes the management and use of these associations simple, and supports multiple types of associations: the first three are the most common, and here we only explain the first three associations

• One-to-one
• One-to-many
• Many-to-many
• Remote one-to-many
• Remote one-to-one
• One-to-one (polymorphic association )
• One-to-many (polymorphic association)
• Many-to-many

Establish model association

One-to-one

Example:
Two data tables: guest User table and guestinfoUser information
where guest The primary key id field in the table corresponds to the foreign key user_id field First create two model files:
php artisan make:model Guest
php artisan make:model Guestinfo
Guest model file:

class Guest extends Model{
    use HasFactory;
    // 设置Guest模型对应的数据表
    protected $table = 'guest';
    // 关闭create_time和update_time字段自动管理
    public $timestamps = false;
    // 设置与guestinfo的关联方法，方法名建议使用被关联表的名字
    public function guestinfo(){
    // hasOne(被关联的名命空间，关联外键，关联的主键)
        return $this->hasOne('App\Models\Guestinfo','user_id','id');
    }}

Guestinfo model file:

class Guestinfo extends Model{
    use HasFactory;
    // 设置Guest模型对应的数据表
    protected $table = 'guestinfo';
    // 关闭create_time和update_time字段自动管理
    public $timestamps = false;
    // 设置与guestinfo的关联方法，方法名建议使用被关联表的名字
    public function guest(){
    // hasOne(被关联的名命空间，关联外键，关联的主键)
        return $this->belongsTo('App\Models\Guest','user_id','id');
    }}

Create a controller to connect the two model files:

php artisan make:controller Controllers
Content:

class Controllers extends Controller{
    //
    public function getOne(){
    // 通过关联方法获取guest表中username = admin记录在guestinfo对应的记录
    // ->guestinfo 是Guest模型文件里面定义的guestinfo方法
        $guestInfo = Guest::firstWhere('username','admin')->guestinfo;
	// 通过关联方法获取guestinfo中id=3 记录在guest表中的对应记录
        $data = Guestinfo::find(3)->guest;
        
        dump($guestInfo);
        // 将模型转换成数组
        dump($data->toArray());
    }}

Create the route of the controller:

Route::get('relative/getOne',[Controllers::class,'getOne']);
Access route: The result is:

One-to-many

Example:

Two data tables: guest
User table and article Article table where the primary key id
field in the guest table corresponds to the foreign key user_id field created in guestinfo article
model file: php artisan make:model Article
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">class Article extends Model{     use HasFactory;     // 设置Guest模型对应的数据表     protected $table = 'article'; // 关闭create_time和update_time字段自动管理         public $timestamps = false;     public function guest(){     // 设置与guest的关联方法,与一对一的从表设置一样         return $this-&gt;belongsTo('App\Models\April\Guest','user_id','id');     }}</pre><div class="contentsignin">Copy after login</div></div>Add an

article# in the

Guest model file ## Method

class Guest extends Model{
    use HasFactory;
    // 设置Guest模型对应的数据表
    protected $table = 'guest';
    // 关闭create_time和update_time字段自动管理
    public $timestamps = false;
    // 设置与guestinfo的关联方法，方法名建议使用被关联表的名字
    public function guestinfo(){
    // hasOne(被关联的名命空间，关联外键，关联的主键)
        return $this->hasOne('App\Models\Guestinfo','user_id','id');
    }
    // 设置与article的关联：hasmany 有很多
     public function article(){
        return $this->hasMany('App\Models\April\Article','user_id','id');
    }}

Test it in the Controllers controller file:

Example 1: Query all articles published by a user: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">  // 查询某个用户发表的所有文章         $article = Guest::find(1)-&gt;article;         // 返回为数据集，需要遍历         foreach ($article as $v){             dump($v-&gt;toArray());         }</pre><div class="contentsignin">Copy after login</div></div>

Example 2: Query the latest article published by a user

		// 查询某个用户最新发表的一篇文章
        // article()生成一个构造器，可以进行筛选
        $article = Guest::find(1)->article()->orderby('created_at','desc')->first();
        dump($article->toArray());

Example 3: Query the name of the publisher of an article through association

		//  通过article和guest关联，再通过guest关联的guestinfo获取姓名
        $name = Article::find(2)->guest->guestinfo;
        dump($name->name);

Example 4: Query the comment information of an article through association
Create Comment model:

php artisan make:model Comment

Comment model code: <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">class Comment extends Model{     use HasFactory;     // 设置Comment模型对应的数据表     protected $table = 'comment';     // 关闭create_time和update_time字段自动管理     public $timestamps = false;     // 设置与article的关联方法，方法名建议使用被关联表的名字     public function article(){         return $this-&gt;belongsTo('App\Models\April\Article','article_id','id');     }}</pre><div class="contentsignin">Copy after login</div></div>Add method comment in the Article model:

public function comment(){
        return $this->hasMany('App\Models\April\Comment','article_id','id');
    }

controller controller code:

$info = Article::find(2)->comment;
        foreach ($info as $v){
            dump($v->toArray());
        }

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