CRUD Operations Explained

What is CRUD?

CRUD (stands for Create, Read, Update and Delete, and sometimes Construct, Retrieve, Update, and Destroy) is a way of working with data in persistent storage. CRUD is four main functions associated with operations performed in the database on data (create, read, update and delete).

What HTTP methods match CRUD operations?

HTTP Verb CRUD Operation Description
POST Create The HTTP POST verb is mainly used to create new resources. After successfully creating a new resource, the POST request should return an HTTP 200x status code. If the server returned the 201 status code, then the Location HTTP header must contain a link to the newly created resource.
GET Read The HTTP GET verb is used to retrieve a resource from the server. A successful GET request should return an HTTP 200 status code along with the requested resource (JSON, XML, PNG, etc.). If an error occurs, a 400x status code is usually returned.
PUT Update/Replace The HTTP PUT verb is used to update an existing resource on the server by completely replacing the existing resource with a new one. After a successful resource update, the PUT request should return an HTTP 200x status code. If the server does not return any content in the response body, it should return a 204 status code.
PATCH Update/Modify The HTTP PATCH command is used to partially update an existing resource on the server instead of the PUT method, which completely replaces an existing resource with a new one. After successfully patching the resource, the PATCH command should return an HTTP 200x status code.
DELETE Delete The HTTP DELETE verb is used to delete an existing resource from the server. On successful deletion, the DELETE request should return an HTTP 200x status code. On error, a 400x status code is usually returned.

What are the basic principles of CRUD operations?

The basic four CRUD operations can be performed on selected data in a SQL database through a graphical user interface, code, or API. These operations are:

  • Create - the create operation adds a new record to the database. In SQL, the Create operation is called the INSERT command.
  • Read - the read operation allows to search for specific records in the database and read their values. In SQL, the read operation is used with the SELECT command. The SELECT command is often used in conjunction with the WHERE command.
  • Update - the update operation is used to modify an existing record in the database. In SQL, the update operation is called the UPDATE command. The UPDATE command is often used in conjunction with the WHERE command.
  • Delete - the delete operation removes a record from the database. In SQL, a delete operation is called a DELETE command. The DELETE command is often used in conjunction with the WHERE command.

What is SQL?

SQL stands for Structured Query Language. SQL is a standard language for relational databases. SQL statements are used to perform tasks such as adding new data to a database, updating existing data, or retrieving existing data from a database. With four standard SQL commands such as SELECT, INSERT, UPDATE, and DELETE, you can do almost anything you need to do.

What is CRUD Testing?

CRUD testing is a black-box testing method to verify that the functionality of a software product meets product requirements. Black-box testing is a type of software testing in which developers are unfamiliar with the database design and architecture of the code. Black box testing also applies to SQL databases and ensures correct data display and data integrity.

What is REST?

REST stands for Representative State Transfer, an architectural style that allows independent computer systems to exchange data in a standard way over the Internet. REST-compliant systems (often referred to as RESTful systems) are stateless and client/server-based systems that use HTTP protocol methods to associate resources with actions within a client-server relationship.

CRUD vs REST: what’s the difference?

CRUD is a set of four operations performed on data storage, usually on database primitives such as tables and records, while REST methods operate on resource representations, each identified by its URL. REST objects are not database primitives but complex object abstractions. CRUD is a standardized way to work with data storage in client/server applications, whereas REST is an architectural style. CRUD operations can be mapped to REST methods.

REST vs CRUD: what's in common?

REST clients interact with REST API servers over the HTTP protocol using a set of HTTP methods for processing data: HTTP POST, GET and DELETE. On the other hand, CRUD operations correspond to these HTTP methods. Therefore there are some similarities between REST API commands and CRUD operations, and we often see CRUD in the context of REST.

REST/HTTP CRUD
POST/PUT CREATE
GET/HEAD READ
PUT/POST/PATCH UPDATE
DELETE DELETE

Conclusion

CRUD is a set of functions for working with a database. Create, Read, Update and Delete (CRUD) are the four main functions for interacting with database applications. CRUD functions often play a notable role in REST web APIs, where they map to the corresponding HTTP methods: GET, POST, PUT, PATCH, and DELETE.

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