• One to one relationships are very straightforward in Laravel. Make sure that one of the tables has a key that references the id of the other table. For example, an ‘address’ table will have a field called user_id . That will reference the users_id field.

• A one-to-one relationship exists when each row in one table has only one related row in a second table. For example, a business might decide to assign one office to exactly one employee. Thus, one employee can have only one office. The same business might also decide that a department can have only one manager.

• A husband- wife relationship is the best example of One To One Relationship. There are two functions uses hasOne() and belongsTo(), both are related to each other. A belongsTo() relationship matches a related table’s ‘id’ to a ‘localKey’ field on ‘this’ model. Another way to think about it is the belongsTo() relationship should live on the model that has the field that links to the related tables id. Basic syntax of both uses in Models:

class Customer extends Model
{
  public function mobile()
  {
    return $this->hasOne(Mobile:class);      //customer and mobile relationship in a model/table.
  }
}

class Mobile extends Model
{

    public function customer()
    {
        return $this->belongsTo(Customer::class);   //relationship from mobile to customer
    }
}

How do I save a one to one relationship in laravel ?

• Step 1 : Install Laravel and Basic Configurations. Each Laravel project needs this thing.
• Step 2 : Create Migration and Model.
• Step 3 : Setup One To One Relationship.
• Step 4 : Inverse Of The Relationship.
• Step 5 : Insert Records.
• Step 6 : Retrieve Records.
• Step 7: Update Records.
• Step 8 : Delete Records.

• Firstly create your laravel project and make two Models, Migrations and Conrollers by:

php artisan make:model Customer -mc

php artisan make:model Mobile -mc

• Now goto both migration table & create a schema.

     Schema::create('customers', function (Blueprint $table)
         {
            $table->id();
            $table->string('name');                     //costomize
            $table->string('email');
            $table->timestamps();
        });

Schema::create('mobiles', function (Blueprint $table) {
            $table->id();
            $table->string('model');                             //costomize
            $table->timestamps();

            $table->unsignedBigInteger('customer_id');                   //customize to link id from          
            $table->foreign('customer_id')->references('id')->on('customers');
        });

See the migration table of customers & mobiles and also its foreign key & index. The id of customer_table to be extends in mobile_table.

• Create a relation in Customer model b/w customer and mobile by hasOne() which are showing above, as well as create two method in CustomerController first insert the data after making both model object and showing the data.

    public function add_customer()

    {

    

        $customer = new Customer();

        $customer->name="sam";

        $customer->email="sam@gmail.com";

        $customer->save();

        

        $mobile = new Mobile();

        $mobile->model = "oppo12";

        $customer->mobile()->save($mobile);   //save mobile on customer


        return $customer;
   }

In this Controller, create a another method to showing mobile_data from customer_id:

    public function show_mobile($id)

    {

        $mobile = Customer::find($id)->mobile;


        return $mobile;

        

     }

• Goto routes ‘web.php’ & makes routes for customer and mobile to display one by one in url:

Route::get('add-customer',[CustomerController::class,'add_customer']);



Route::get('show-mobile/{id}',[CustomerController::class,'show_mobile']);

Route::get('show-customer/{id}',[MobileController::class,'show_customer']);

• Similar, create a relation in Mobile model b/w mobile & customer by above belongsTo() and create a method in MobileController for showing data by mobile_id.

public function show_customer($id)

    {

        $customer = Mobile::find($id)->customer;

        return $customer;  


    }

Finally there is relationship between Customer and Mobile. Remember we don’t forget to import both models in both controller class and controller in routes.

<strong>For Controllers</strong>:
use App\Models\Customer;

use App\Models\Mobile;

<strong>For routes:</strong>
use App\Http\Controllers\CustomerController;

use App\Http\Controllers\MobileController;

Laravel includes Eloquent, an object-relational mapper (ORM) that makes it enjoyable to interact with your database. In addition to retrieving records from the database table, Eloquent models allow you to insert, update, and delete records from the table as well. The Eloquent ORM included with Laravel provides a simple Active Record implementation for working with your database. Each database table has a corresponding “Model” which is used to interact with that table. Before getting started, be sure to configure a database connection in config/database .

Why we use eloquent ORM ?

Eloquent is an ORM, which means can automatically handle the relationships of your models for you. You can retrieve related models without writing complex queries. You can even retrieve database information without any kind of database knowledge at all. while Object–relational mapping (ORM, O/RM, and O/R mapping tool) in computer science is a programming technique for converting data between incompatible type systems using object-oriented programming languages.

How we use ORM model for create and show columns in migration table ?

• Firstly create a database if you want then customize it your project .env .

• After that, create a migration table, Controller class and Model class by just a command:

php artisan make: model Employee -mc 

• Then create a schema into migration table and migrate it:

• After that you just open Controller class and import model class as “use App\Models\Employee” and create two anonymous class either firstOrCreate() or firstOrNew() into controller class as:

$employee = Employee :: <strong>firstOrCreate</strong>
(
   ['name' => "shubham"],
   ['email'=>"shubham@gmail.com",'city'=>"allahabad",'marks'=> "50"]  
);

• While, in firstOrNew() you should be add save() for fetching and inserting a data:

$employee = Employee :: <strong>firstOrNew</strong>
(
   ['name' => "shubham"],
   ['email'=>"shubham@gmail.com",'city'=>"allahabad",'marks'=> "50"]  
);
  $employee -> save();

• Before all this, you must be added fillable property into model class for assigning the data which is:

protected $fillable = ['name','email','city','salary']; 

Laravel Migration is an essential feature in Laravel that allows you to “easily create a table in your database“. It allows you to create and modify the application’s database schema. You can modify the table by adding a new column or deleting an existing column. Migrations are like version control for your database. Migration tables are files that are created by an administrator.

2. Why do we use migrations?

Another common reason for migration is to move from an outdated system or legacy systems to a system that is designed for modern data needs. In the age of big data, new storage techniques are a necessity. For example, a company might choose to move from a legacy SQL database to a data lake or another flexible system.

3. What are the two essential method and it’s use?

There are two methods, first is up() method and second is down() method. In up() method we create an schema like column of create_table. while in down() method, we rollback a current migration table. in other way we can say both method are opposite to each other. One create a table and second drop the table. Take a look both methods operation:

public function <strong>up()</strong>   //create a schema of a table
    {
        Schema::create('table_name', function (Blueprint $table) {
            $table->id();

            .
            .
            $table->timestamps();
        });
    }
  

    public function <strong>down()</strong>       //use for the rollback the table.
    {
        Schema::dropIfExists('table_name');
    }

php artisan make: migration create_yourtable

Schema::create('yourtable', function (Blueprint $table) {
            $table->id();            //it's autogenerated
            $table->String('name)
           
            $table->timestamps();
        });

php artisan migrate

php artisan migrate --path=/database/migrations/2020_04_01_064006_create_posts_table.php

php artisan migrate: status

php artisan migrate: rollback

What is CRUD and its purpose ?

The full form meaning of CRUD is “Create” “Retrieve” “Update” and “Delete“. In computer programming, create, read, update, and delete (CRUD) are the four basic operations of persistent storage. CRUD is also sometimes used to describe user interface conventions that facilitate viewing, searching, and changing information using computer-based forms and reports. CRUD operations are basic data manipulation for database.

The ability to create, read, update and delete items in a web application is crucial to most full stack projects. CRUD is too important to be ignored, so learning it first can really improve confidence within unfamiliar stacks.

Why to use CRUD using SQL query builder?

Laravel is described by its creators as the framework for web artisans. It’s based on the MVC (Model-View-Controller) pattern and can be used for easily creating apps for making CRUD (Create, Retrieve, Update, Delete) operations against a database. For example, if we’re creating a store front, blog posting page, todo list or social media clone, without CRUD actions we’ll get stuck very quickly.

How to use CRUD operation using Query builder in Laravel ?

We operate CRUD functions in six steps like:

• Step 1 : Install Laravel 8.
• Step 2: Database Configuration.
• Step 3: Create Migration.
• Step 4: Add Resource Route.
• Step 5: Add Controller and Model.
• Step 6: Add Blade Files.

Firstly create a database in your XAMPP server.

• Open XAMPP and start mysql as well as apache server.
• Then hit localhost in url for opening phpmyadmin and create a database.

Next, create a project and migration table.

laravel new your_project

• After that, go to the project directory and entering the command:

php artisan make: migration createmytable 

• Open this migration table and just create a schema for a table like:

Schema::create('tablename',function(Blueprint $table)
{
  $table->id();
  $table->String('col1');
  $table->String('col2');
  .
  .
});

• After that , you just migrate it by entering ‘php artisan migrate‘.

Next, create a Controller class and mentioned it in routes.

• Just enter a command into terminal. it create all CRUD methods in controller class:

php artisan make: controller mycontroller -r

• Before CRUD operation, we just make main view file by adding simple css, js bootstrap. then we insert the code into index() to view the table.

index()
{
  $table = DB::table('tablename') -> get();
  return view ('mainblade',['mytable'=>table]);
}

• while in create() , you just write a schema in create method like insert query:

create(Request $request)
{
  DB::table('tablename')->insert(
  [ col1 =>$request->col1; 
    col2 =>$request->col2; 
    .
    .
  ]);
 return redirect (route('index'))->with('status',"Data created");
}

• To edit/update the data, just write the code into edit() and update().

edit()
{
 $table = DB::table('tablename')->find($id);
 return view('editblade',['mytable'=>$table]);
}

update(Request $request,$id)
{
  DB::table('tablename')->where('id',$id)->update(
  [
    'col1' => $request->col1,
    'col2' => $request->col2,
     .
     .
  ]);
  return redirect(route('index'))->with('status',"Data updated");
}

• At the end, we can delete the table by using delete query in destroy method of Controller class like:

destroy()
{
 DB::table('tablename')->where('id', $id)->delete();
 return redirect(route('index'))->with('status', "Data deleted")
}

What is variable in programming languages?

• In computer programming, a variable is a storage location (identified by a memory address) paired with an associated symbolic name.
• It contains some known or unknown quantity of information referred to as a value.
• Finally A variable is a container for a particular type of data (like integer, float, String etc).

example: Java:: int num, String name;

Php:: $num (there is not necessary for type)

Kotlin:: var num, val num2;

What is keys using in Php and how we use it?

Php is used by embedding with HTML, due to which some new features can also be added to it. The specialty of this language is that it is used to design “Dynamic website”. When a user sends a request to a php web page from his browser, in which this code resides.

<?php
  <h1>Welcome to {{$name}} </h1>     //$name is variable but it comes from name key.
  @include ('address',['<strong>pin</strong>'=>212303])    //here, pin is an key which is not use in this page.
?>

**In foreach use $key => $value

foreach($featured as $key => $value)
{
  echo $value['name'];
}

What is use of tuple in Programming language?

Tuple is used to store multiple objects in a single variable. Tuple is similar to list because the value of the objects stored in the list can be changed, whereas tuple is immutable so the value of the objects stored in the tuple cannot be changed.

example:

[Geeks, 123, &#*@]
key value[A, B]

<?php
    $value= 10;
    echo "$value is good price of the product"; //<strong>String interpolation</strong>
    echo '$value is good price of the product';
?>

<strong><?php
  $name = "product";
  echo $name;
?></strong>

product