In the software development world, CRUD consists of four operations - create,
read, update, and delete.
- Create: This operation would create a brand new entity. In terms of
database, this would be an
INSERT statement.
- Read: This operation would read something from the database and would not
make any permanent changes to the database. In terms of database, this would
be a
READ operation.
- Update: This operation would change an already existing entity. In terms
of database it would be an
UPDATE operation.
- Delete: This operation would delete an entity. In terms of database this
would be a
DELETE operation.
CRUD in action
In Rails each resource typically performs these seven operations:
| VERB | URI Pattern | Controller#Action | Used for | Operation |
|---|
| GET | /books | books#index | List books | READ |
| POST | /books | books#create | Create a book | CREATE |
| GET | /books/new | books#new | Form for a new book | READ |
| GET | /books/:id/edit | books#edit | Form for editing book | READ |
| GET | /books/:id | books#show | Show info about book | READ |
| PATCH | /books/:id | books#update | Update info about book | UPDATE |
| PUT | /books/:id | books#update | Update info about book | UPDATE |
| DELETE | /books/:id | books#destroy | Delete info about book | DELETE |
As we can see each of those seven actions could be assigned to one of these four
operations - Create, Read, Update and Delete.
REST and CRUD
REST is an architectural system that deals with data through HTTP protocols.
More info about REST is
here.
Typically software applications create RESTful APIs to handle CRUD operations.
More info about CRUD operations is
here.
There aren't any changes to the application in this chapter. So let us clean up
any accidental changes.