What is the Difference between Active record and ORM in rails?

Question

Is there any difference between Actice Record and ORM? some of the documentations says both are same. is that true?

Answer 1

Object Relational Mapping (ORM) is the technique of accessing a relational database using an object-oriented programming language. Object Relational Mapping is a way to manage database data by "mapping" database tables to classes and instances of classes to rows in those tables.

Active Record is just one of such ORMs, others include:

• Sequel
• DataMapper
• Squeel
• Ruby Object Mapper etc.

Read more here https://github.com/learn-co-students/active-record-mechanics-crud-v-000#orm-vs-active-record

Answer 2

Object Relational Mapping (ORM):

simplify the use of databases in applications.

Use objects to hold database records

1. One class for each table in the database
2. Objects of the class correspond to rows in the table

3. Attributes of an object correspond to columns from the row

   • Manage the movement of information between objects and the back-end database.
   • Manage relationships between tables (joins), turn into linked data structures.

ActiveRecord Basics

Model: A Rails class corresponding to a database table ActiveRecord:

• Base class for models in Rails
• Implements Object Relational Mapping

Example Table

<table>
  <tbody>
    <tr>
      <th> id </th>
      <th>name</th>
      <th>birth</th>
      <th>gpa</th>
      <th>grade</th>
    </tr>
  </tbody>
  <tbody>
    <tr>
      <td> 1 </td>
      <td> Anderson </td>
      <td> 1987-10-22 </td>
      <td>  3.9 </td>
      <td>  2009  </td>
    </tr>
     <tr>
      <td> 2 </td>
      <td> Jones </td>
      <td> 1990-04-16</td>
      <td> 2.4 </td>
      <td>  2012   </td>
    </tr>
 </tbody>
  
  </table>

Create a class for this table (app/models/student.rb):

class Student < ActiveRecord::Base
end

Or, just use the script/generate program:

ruby script/generate model student

• ActiveRecord examines the database schema for this table and makes appropriate attributes and methods available in the class automatically