Laravel introductory tutorial: The relationship between tables

##First of all, about the relationship between tables

1.One-to-one

2.One-to-many

3.Many-to-one

4.Many-to-many

Distinguish between parent table and child table

1. The "one" side is the parent table

2. The "many" side It is a child table

How to deal with one-to-many relationships

Create a field (foreign key) in the child table to point to the parent table

How to deal with many-to-many relationships

Create an intermediate table to convert the "many-to-many" relationship into "one-to-many"

Case analysis

Table 1: User table (it_user)

Table 2: User details table (it_user_info)

Table 3: Article table (it_article)

Table 4: Country table (it_country)

Table 5: User role table (it_role)

① One-to-one

The user table (Table 1) and the details table (Table 2) have a one-to-one relationship

②One-to-many

The user table (Table 1) and the article table ( Table 3) is a one-to-many relationship

③Many-to-one

The user table (Table 1) and the country table (Table 4) are a many-to-one relationship

④Many-to-many

The user table (Table 1) and the role table (Table 5) are a many-to-many relationship

User table creation and test data

DROP TABLE IF EXISTS `it_user`;
CREATE TABLE `it_user` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '主键',
  `name` varchar(64) DEFAULT NULL COMMENT '用户名',
  `password` char(32) DEFAULT NULL COMMENT '密码(不使用md5)',
  `country_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `国家id` (`country_id`)
) ENGINE=MyISAM AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of it_user
-- ----------------------------
INSERT INTO `it_user` VALUES ('1', 'xiaoming', '123456', '1');
INSERT INTO `it_user` VALUES ('2', 'xiaomei', '123456', '1');
INSERT INTO `it_user` VALUES ('3', 'xiaoli-new', '123', '1');

User details table creation and test data

-- ----------------------------
-- Table structure for it_user_info
-- ----------------------------
DROP TABLE IF EXISTS `it_user_info`;
CREATE TABLE `it_user_info` (
  `user_id` int(11) NOT NULL AUTO_INCREMENT,
  `tel` char(11) DEFAULT NULL,
  `email` varchar(128) DEFAULT NULL,
  `addr` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`user_id`)
) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of it_user_info
-- ----------------------------
INSERT INTO `it_user_info` VALUES ('1', '13012345678', 'xiaoming@163.com', '北京');
INSERT INTO `it_user_info` VALUES ('2', '15923456789', 'xiaomei@163.com', '上海');
INSERT INTO `it_user_info` VALUES ('3', '18973245670', 'xiaoli@163.com', '武汉');

Article table creation and test data

-- ----------------------------
-- Table structure for it_article
-- ----------------------------
DROP TABLE IF EXISTS `it_article`;
CREATE TABLE `it_article` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) DEFAULT NULL,
  `content` text,
  `user_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `user_id` (`user_id`)
) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of it_article
-- ----------------------------
INSERT INTO `it_article` VALUES ('1', '世界那么大，我想去看看', '钱包那么小，总是不够', '1');
INSERT INTO `it_article` VALUES ('2', '我想撞角遇到爱', '却是碰到鬼', '2');
INSERT INTO `it_article` VALUES ('3', '哈哈哈哈', '嘻嘻嘻嘻', '1');

Country Table creation and test data

-- ----------------------------
-- Table structure for it_country
-- ----------------------------
DROP TABLE IF EXISTS `it_country`;
CREATE TABLE `it_country` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of it_country
-- ----------------------------
INSERT INTO `it_country` VALUES ('1', '中国');
INSERT INTO `it_country` VALUES ('2', '美国');

User role table creation and test data

-- ----------------------------
-- Table structure for it_role
-- ----------------------------
DROP TABLE IF EXISTS `it_role`;
CREATE TABLE `it_role` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of it_role
-- ----------------------------
INSERT INTO `it_role` VALUES ('1', '开发');
INSERT INTO `it_role` VALUES ('2', '测试');
INSERT INTO `it_role` VALUES ('3', '管理');

User and role intermediate table creation and testing Data

-- ----------------------------
-- Table structure for it_user_role
-- ----------------------------
DROP TABLE IF EXISTS `it_user_role`;
CREATE TABLE `it_user_role` (
  `user_id` int(11) DEFAULT NULL,
  `role_id` int(11) DEFAULT NULL,
  KEY `role_id` (`role_id`),
  KEY `user_id` (`user_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of it_user_role
-- ----------------------------
INSERT INTO `it_user_role` VALUES ('1', '1');
INSERT INTO `it_user_role` VALUES ('1', '2');
INSERT INTO `it_user_role` VALUES ('1', '3');
INSERT INTO `it_user_role` VALUES ('2', '1');
INSERT INTO `it_user_role` VALUES ('3', '2');

Preparation work

1. Planning routing

In routes/ Write the following route under web.php:

//ORM的关联关系
Route::get('/orm/relation/{mode}','ORM\UserController@relation');

2. Write the relation method in App/Http/Controllers/ORM/UserController.php

    public function relation($mode)
    {
        switch ($mode){
            case '1_1':
            {
                //一对一
            }
            break;
            case '1_n':
            {
                //一对多
            }
                break;
            case 'n_1':
            {
                //多对一
            }
                break;
            case 'n_n':
            {
                //多对多
            }
                break;
            default;
        }
    }

3. Install the debug debugging tool

3.1 Use the composer command to install

composer require  barryvdh/laravel-debugbar

3.2. Modify the config/app.php file, load debugbar to laravel into the project, and add it to the 'providers' array The following configuration:

Barryvdh\Debugbar\ServiceProvider::class,

In addition to installing the debugbar debugging tool, you can also use query monitoring: Add the following code to the boot method of providers/AppServiceProvider.php

\DB::listen(function ($query) {
    var_dump($query->sql);
     var_dump($query->bindings);
     echo &#39;<br>&#39;;
 });

You can also print out the executed sql statement.

One-on-one

1. Create the Userinfo model object

Enter the cmd command line. Executing the following command in the directory where the laravel project is located

php artisan make:model Userinfo

will generate Userinfo.php in the App directory

2. Edit the Userinfo model file

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Userinfo extends Model
{
    protected $table  =  &#39;user_info&#39;;
    protected $primaryKey = &#39;user_id&#39;;
    protected $fillable = [&#39;user_id&#39;,&#39;tel&#39;,&#39;email&#39;,&#39;addr&#39;];
    public    $timestamps = false;
}

3. Write UserModel and add one-to-one method

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class UserModel extends Model
{
    protected $table = &#39;user&#39;;//真是表名
    protected $primaryKey = &#39;id&#39;;//主键字段，默认为id
    protected $fillable = [&#39;name&#39;,&#39;password&#39;];//可以操作的字段
    public $timestamps = false;//如果数据表中没有created_at和updated_id字段，则$timestamps则可以不设置，
    默认为true
    public function Userinfo()
    {
        /*
         * @param [string] [name] [需要关联的模型类名]
         * @param [string] [foreign] [参数一指定数据表中的字段]
         * */
        return $this->hasOne(&#39;App\Userinfo&#39;,&#39;user_id&#39;);
    }

4. Write UserController and call one-to-one method

    public function relation($mode)
    {
        switch ($mode){
            case '1_1':
            {
                //一对一
                $data = UserModel::find(1)->Userinfo()->get();
                dd($data);
            }
            break;
            default;
        }
    }

One-to-many

1. Create the article model object

Execute the command

php artisan make:model Article

Generate the Article.php file under the app

2. Write article model file

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Article extends Model
{
    protected $table = &#39;article&#39;;
    protected $primaryKey = &#39;id&#39;;
    protected $fillable = [&#39;id&#39;,&#39;title&#39;,&#39;content&#39;,&#39;user_id&#39;];
    public $timestamps  = false;
}

3. Write UserModel and add one-to-many method

public function Artice()
    {
        return $this->hasMany('App\Article','User_id');
    }

4. Write UserController and call one-to-many method

    public function relation($mode)
    {
        switch ($mode){
            case '1_1':
            {
                //一对一
                $data = UserModel::find(1)->Userinfo()->get();
                dd($data);
            }
            break;
            case '1_n':
            {
                //一对多
                $data = UserModel::find(1)->Artice()->get();
                dd($data);
            }
                break;
            default;
        }
    }
}

many-to-one

1. Create country model Object

executes the command

php artisan make:model Country

2. Write the country model file

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Country extends Model
{
    protected $table = &#39;country&#39;;   //真实表名
    protected $primaryKey = "id";   //主键id
    protected $fillable = [&#39;id&#39;,&#39;name&#39;];    //允许操作的字段
    public $timestamps = false; //如果数据表中没有created_at和updated_id字段，则$timestamps则可以不设置，
    默认为true
}

3. Write the UserModel and add many-to-one Method

public function Country()
{
    return $this->belongsTo('App\Country','country_id');
}

4. Write UserController and call method

public function relation($mode)
    {
        switch ($mode){
            case '1_1':
            {
                //一对一
                $data = UserModel::find(1)->Userinfo()->get();
                dd($data);
            }
            break;
            case '1_n':
            {
                //一对多
                $data = UserModel::find(1)->Artice()->get();
                dd($data);
            }
                break;
            case 'n_1':
            {
                //多对一
                $data = UserModel::find(1)->Country()->get();
                dd($data);
            }
                break;
            default;
        }
    }
}

Many-to-Many

1. Create role model object

Execute command

php artisan make:model Role

Execute command

php artisan make:model User_role

2.Write Role model

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Role extends Model
{
    protected $table = &#39;role&#39;;
    protected $primaryKey = "id";
    protected $fillable = [&#39;name&#39;];
    public $timestamps  =false;
}

Write the User_role model

Because there is no primary key field in the table, two fields are needed

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class User_role extends Model
{
    protected $table = &#39;user_role&#39;;
    public $timestamps  =false;
}

3. Write the UserModel and add the many-to-many method

    public function Role(){
        /*
         * 第一个参数：要关联的表对应的类
         * 第二个参数：中间表的表名
         * 第三个参数：当前表跟中间表对应的外键
         * 第四个参数：要关联的表跟中间表对应的外键
         * */
        return $this->belongsToMany('App\Role','user_role','user_id','role_id');
    }

4. Write UserController and call the many-to-many method

public function relation($mode)
{
    switch ($mode){
        case '1_1':
        {
            //一对一
            $data = UserModel::find(1)->Userinfo()->get();
            dd($data);
        }
        break;
        case '1_n':
        {
            //一对多
            $data = UserModel::find(1)->Artice()->get();
            dd($data);
        }
            break;
        case 'n_1':
        {
            //多对一
            $data = UserModel::find(1)->Country()->get();
            dd($data);
        }
            break;
        case 'n_n':
        {
            //多对多
           $data = UserModel::find(2)->Role()->get();
           dd($data);
        }
            break;
        default;
    }
}

Summary:

1. One pair One usage method: hasOne()

2. One-to-many usage method: hasMany()

3. Many-to-one usage method: belongsTo()

4. Many How to use many: belongsToMany()

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