Examples of how laravel uses with preload (eager to load) and nested query

with() What method can do ？ In what scenarios ？

1. The scene is as follows .2 Data sheets Main table userinfors User table 【id,name,created_at】, From table article table articles surface 【id,user_id,title,content,created_at】
3. demand ： According to the current login user A obtain A Published articles .
4. The relationship between models ： One to many , One user can have multiple articles .

Table structure

1. Main table （userinfors）

2. From the table （articles）

Code implementation （ According to the current login user , Get all relevant articles under the user ）

1. establish model（ I'm not going to go over it here ）
2. In the main table model(userinfor surface ) Create a one to many relationship in the model

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Tests\Controllers\UserController;

/** *  Front end user model  * Class UserInfor * @package App\Models */
class UserInfor extends Model
{
    
    use HasFactory;

    // The table name associated with the model 
    protected $table = 'userinfors';

    // Please fill in the drop down array for attributes that cannot be copied in batch 
    protected $guarded = [];

    // Model serialization ：Date  Type conversion 
    protected $casts = [
        'created_at' => 'date:Y-m-d H:i:s',
        'updated_at' => 'date:Y-m-d H:i:s',
    ];

    /** *  User model one to many associated user dynamic table  *  A user has multiple pieces of dynamic data  *  Parameters 1： Model to associate （ From the table ） *  Parameters 2： That exists in the slave table and userinfor（ Main table ） Associated fields  *  Parameters 3： The one that exists in the main table and   Field names associated from the table  */
    public function article_hasMany()
    {
    
        return $this->hasMany(Article::class,'user_id','id');
    }

}

3. In the controller Controller To realize with

<?php

namespace App\Http\Controllers\Api\V1;

use App\Http\Controllers\BaseController;
use App\Http\Controllers\Controller;
use App\Models\Article;
use App\Models\UserInfor;
use Illuminate\Http\Request;

/** *  User dynamic controller  * Class UserDynamicController * @package App\Http\Controllers\Api\V1 */
class ArticleController extends Controller
{
    
   
    // Get the dynamic list of currently logged in users 
    public function getMyDynamicList(Request $request){
    
        // Receive the necessary parameters 
        $page = $request['page'] ?? 1;// Pagination 
        $limit = 2;// Number of data bars per page 
        $offset = $page * $limit - $limit;// Read from the first few   The default is 0 strip 
        // Query the dynamic data of the current user （ Reverse order ）
        $user_id = UserInfor::where('id',1);// Get the currently logged in user model 
        // Query the articles under the current user , And paging , each page 2 Data , Arrange the articles in reverse order according to their creation time .
        $data_list = $user_id->with(['article_hasMany'=>function($query) use($offset,$limit){
    
        	// Be careful ： The fields called in this closure are all associated model In the field （ That is, the fields that exist in the slave table , There is no need to consider the problem that the field name of the secondary table is duplicate with that of the primary table .）
        	// As the following example ：$query->orderBy(' From the table created_at','desc')->offset($offset)->limit($limit);
            $query->orderBy('created_at','desc')->offset($offset)->limit($limit);
        }])->first();
	
		dd($data_list->toArray());//laravel The print function provided by the framework , The effect is the same as below 2 Line code .
        //var_dump($data_list->toArray());
        //die;
    }


}

4. Return data structure

array:25 [
  "id" => 1
  "created_at" => null
  "name" => " Liu Tong "
  "articles" => array:2 [
    0 => array:5 [
      "id" => 2
      "created_at" => "2020-10-26 10:36:59"
      "user_id" => 1
      "title" => " The writer A-2"
      "content"=>" Content A-2 Content A-2 Content A-2 Content A-2"
    ]
     1 => array:5 [
      "id" => 1
      "created_at" => "2020-10-22 12:36:59"
      "user_id" => 1
      "title" => " The writer A-1"
      "content"=>" Content A-1 Content A-1 Content A-1 Content A-1"
    ]
  ]
]

4. summary ：
In brief, why do I use this with() Method ： This is because he compressed mysql Query statement , Change the query statement to 2 strip .
Article 1 check the designated user .
Article 2 check be-all Specify article .
sql To run 2 All over .

But the routine will run N+1 All over
Check the specified user for the first time .
Check the assigned articles for the second time .
The first … Look up the assigned article .
The first N Check the specified articles .
This is not very database friendly , We all know the shortcomings , I won't go into details .

5. Combat code

// Get the dynamic list of currently logged in users 
    public function getMyDynamicList(Request $request){
    
        // Receive the necessary parameters 
        $page = $request['page'] ?? 1;// Pagination 
        $limit = 12;// Number of data bars per page 
        $offset = $page * $limit - $limit;// Read from the first few   The default is 0 strip 
        // Query the dynamic data of the current user （ Reverse order ）
        $user_infor = UserInfor::where('token',$request['token']);
        $data_list = $user_infor->with(['userDynamics'=>function($query) use($offset,$limit){
    
            $query->orderBy('created_at','desc')->offset($offset)->limit($limit);
            $query->withCount('userDynamicComments as connent_count');// Parameters 1, The associated method name in the model ,as *  Represents the alias of the return value 
            $query->withCount('userDynamicAdmiress as admiress_count');
        }])->select('id','nickname','pic_url')->first();

    }

with Loop nesting usage

1. Use scenarios ： When 3 How to write circular nesting when you want to create an association .

Take an inappropriate example ！
What if ： existing 3 The tables are A: Book list ,B: Comment table ,C: Reviewer phone list .
Table relations ： Be careful ： The same book can only be commented by the same person once ！（ That is, a book can have multiple comments , But the reviewer of each comment can only be associated with the book once ！）
Book list （ One ） Yes Comment table （ many ） = One to many connection .
Comment table （ One ） Yes Commentator （ One ） = One to one connection .
demand ： It is known that Books id And Designated comments id, Based on Books id It can be concluded by inquiry Comment content as well as Reviewer phone data
Table structure diagram ：
A： Book list (book)

id	name( Book name )
1	my php file
2	My overtime history
3	My work record

B： Comment table (comment)

id	comment（ Comment content ）	book_id（ The Secretary table is related to id）	tel_id( Phone list Association id)
1	This book is really thick	1	18
2	My eyes are full of tears	1	43
3	Is this really a daily record ？ It's very detailed	2	69

C： Reviewer phone list （tel）

id	comment_id（ Comment table id）	tel( Reviewer phone number )
18	1	183******3645
…	…	…
43	2	133******2625
…	…	…
69	3	131******1661

2. Use with() The code implements circular nested queries

// According to the specified book id  And   Designated comments id  Get current book data .
    public function getBookParticulars(Request $request){
    
        // Receiving books id
        $book_id = $request->book_id;// Books id
        $comment_id = $request->comment_id;// Designated comments id

        //bookComment =  Books Book The model defines the name of the one to many relevance review method 
        //commentTel =  Comment content table one-to-one related reviewer telephone list 
        $book = Book::where('id',$book_id)->with(['bookComment'=>function($query) use ($comment_id){
    
        	//$comment_id  The front end is passed to php Method parameters , need use Can be in with Use in 
            $query->where('comment_id',$comment_id)

                #->with('commentTel:id,tel')// Nesting A  In this line of code ‘id’ It's the reviewer phone list （tel） Of id, Don't write this id May result in no query results 

                ->with(['commentTel'=>function($query2){
    
                    $query2->first();
                }])// Nesting B

                ->first();
        }])->first();

        dd($book);// Print data view results 
    }