Association is the relationship between two models. By using associations we can join tables. It is like a glue between different related models. Cakephp provides us very powerful feature of linking models together, just by call of one function. In CakePHP, relations between the database tables are defined through association. Association shows how one model is connected to another model. For this we have to define associations in models, then we can use this wonderful functionalities.

There are four types of associations in cakephp :

 
1. hasOne: Has one-to-one relationship between both tables. has One association is used when there is one to one relation.
 Ex:- A user can have only one department.
  

<?php    
    App::uses('AuthComponent', 'Controller/Component');

    class User extends AppModel {
      public $hasOne = array(
            'Department' => array(
                'className' => 'Department',
                'conditions' => array('User.id = Department.user_id'),
                'order' => ''
            )
        );
    }

2. hasMany: Has one-to-many relationship between both tables. This association is used when there is one to many relations.

Ex:- An author can have more than one books in books table.

<?php
    App::uses('AuthComponent', 'Controller/Component');
    class Author extends AppModel {
      public $hasMany = array(
            'Book' => array(
                'className' => 'Book',
            )
        );
    }

3. belongsTo: Has many-to-one or one-to-one relationship between both tables. This association is used when there is many to one relation.

Ex:- Many books can have one author.

<?php
    App::uses('AuthComponent', 'Controller/Component');
    class Book extends AppModel {
    public $belongsTo = array(
        'Author' => array(
            'className' => 'Author',
            'conditions' => array('Book.auth_id = Author.id'),
            'order' => ''
        )
    );

4. hasAndBelongsToMany (HABTM):  is many-to-many relationship between both tables. This is used when there is many to many relations.

Ex:- Recipes can have many ingredients and ingredients can belong to many reciepes.