Laravel[Eloquent ORM简介、模型的建立及查询数据]

注：以下知识点可能有不全面之处，望见谅

NO.1Eloquent ORM简介

1. Laravel所自带的Eloquent ORM是一个优美、简洁的ActiveRecord实现，用来实现数据库操作
2. 每个数据表都有与之相对应的“模型（Model）”用于和数据交互

NO.2模型的建立

最基础的模型代码如下:

namespace App;

use Illuminate\Database\Eloquent\Model;

class Student extends Model
{
	//指定表名
	protected $table = 'student';
	//指定id
	protected $primaryKey = 'id';
}

将他创建于app目录下，命名为Student.php

NO.3查询数据

首先在查询之前，我先让你们看一下我的数据库

数据如上，然后查询

1.all方式

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
            $students = Student::all();
            dd($students);
	}
}

显示数据库里的所有数据

2.find方式

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
            $students = Student::find(1);
            dd($students);
	}
}

查找指定数据

3.findOrFail方式

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
            $students = Student::findOrFail(1);
            dd($students);
	}
}

如果他没查到指定的数据，那么他会报错，而find若是没有查到该函数，只会弹出一个null

4.查询构造器的使用

1.get方式使用

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
            $students = Student::get();
            dd($students);
	}
}

他会得到一个完整的数据信息，和原本的意义没有区别

2.first方式使用

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::where('id','>',1)
         ->orderBy('age','desc')
         ->first();
         dd($student);
	}
}

当id大于一的时候，获取一个最大值的age

3.where方式使用

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::where('id','>',1)
         ->get();
         dd($student);
	}
}

4.chunk方式使用

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::chunck(2,function($student){
			var_dump($student);
		});
	}
}

5.聚合函数的使用

1.count函数

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::count();
         dd($student);
	}
}

2.max函数

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::max('age');
         dd($student);
	}
}

3.min函数

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::min('age');
         dd($student);
	}
}

4.avg函数

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::avg('age');
         dd($student);
	}
}

5.sum函数

代码如下:

namespace App\Http\Controllers;

use App\Student;

use Illuminate\Support\Facades\DB;

class StudentController extends Controller
{
	 public function orm1()
    {
         $student = Student::sum('age');
         dd($student);
	}
}