Create, Read, Update, and Delete (CRUD) make up the four basic operations of persistent storage. CRUD operations often refer to SQL operations used in relational databases, but can also map to data manipulation operations used in RESTful API services and other databases.
Create
Create operation refers to adding new data or records in a system. In SQL, the
CREATE operation maps to the INSERT statement. For RESTful APIs, POST and
PUT HTTP methods are used to create new records.
Read
Read operation involves retrieving stored data from a system. In SQL, the
SELECT keyword is used, whereas the GET HTTP method is used in RESTful APIs.
Update
Update operation modifies or replaces existing data. In SQL, the UPDATE
keyword is used. For RESTful APIs, the PUT keyword is used to replace entire
records, whereas PATCH is used for partial updates.
Delete
Delete operation is used to remove existing records from a system. For both SQL
and RESTful APIs, the DELETE keyword is used to invoke delete operations.
Use Cases
Applications that support CRUD operations tend to be transactional use cases, where individual inserts, reads, updates, and deletions are common. On the other hand, analytical applications have different data storage and access patterns where CRUD operations are less useful. For example, in analytical applications, it is very common to insert data in bulk, then read data on aggregated values rather than for individual data points. Data may be eventually deleted in bulk often with no support for updates.