Backend Development › Relational Databases & SQL

CRUD

Create, Read, Update, Delete: the four basic data operations.

Also known as: create read update delete

CRUD stands for Create, Read, Update and Delete. These four operations cover most of what an application does with stored data. In SQL, they map to INSERT, SELECT, UPDATE and DELETE:

INSERT INTO books (title) VALUES ('Dune');             -- Create
SELECT id, title FROM books WHERE id = 1;              -- Read
UPDATE books SET title = 'Dune Messiah' WHERE id = 1;  -- Update
DELETE FROM books WHERE id = 1;                        -- Delete

Web APIs often map the same operations onto HTTP methods, typically POST for create, GET for read, PUT or PATCH for update, and DELETE for delete.

The classic mistake is an UPDATE or DELETE without a WHERE clause. It applies to every row in the table, not just the one you meant. Before running one by hand, write the WHERE first and run a SELECT with the same condition to check which rows it matches. When several changes must succeed together, wrap them in a transaction so you can roll back if one fails.