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In computer programming, create, read, update, and delete (CRUD) are the four basic operations of
persistent storage In computer science, persistence refers to the characteristic of state of a system that outlives (persists more than) the process that created it. This is achieved in practice by storing the state as data in computer data storage. Programs have t ...
. CRUD is also sometimes used to describe
user interface In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine fr ...
conventions that facilitate viewing, searching, and changing information using computer-based forms and
report A report is a document that presents information in an organized format for a specific audience and purpose. Although summaries of reports may be delivered orally, complete reports are almost always in the form of written documents. Usage In ...
s. The term was likely first popularized by James Martin in his 1983 book ''Managing the Data-base environment''.


Conceptual

Data can be put in a ''location/area'' of a storage mechanism. * The fundamental feature of a storage location is that its ''content'' is both ''readable'' and ''updatable''. * Before a storage location can be read or updated it needs to be ''created''; that is allocated and initialized with content. * At some later point, the storage location may need to be ''destructed''; that is finalized and deallocated. Together these four operations make up the basic operations of storage management known as CRUD: ''Create'', ''Read'', ''Update'' and ''Delete''.


Databases

The acronym CRUD refers to the major operations which are implemented by
database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases span ...
s. Each letter in the acronym can be mapped to a standard Structured Query Language (SQL) statement. Although relational databases are a common persistence layer in software applications, numerous other persistence layers exist. CRUD functionality can for example be implemented with document databases, object databases,
XML database An XML database is a data persistence software system that allows data to be specified, and sometimes stored, in XML format. This data can be queried, transformed, exported and returned to a calling system. XML databases are a flavor of document ...
s, text files, or binary files. Note: Some
big data Though used sometimes loosely partly because of a lack of formal definition, the interpretation that seems to best describe Big data is the one associated with large body of information that we could not comprehend when used only in smaller am ...
systems do not implement UPDATE, but have only a timestamped INSERT (journaling), storing a completely new version of the object each time.


RESTful APIs

The acronym CRUD also appears in the discussion of RESTful APIs. Each letter in the acronym may be mapped to a Hypertext Transfer Protocol (HTTP) method: In HTTP, the GET (read), PUT (create and update), POST (create - if we don't have `id` or `uuid`), and DELETE (delete) methods are CRUD operations as they have storage management semantics, meaning that they let
user agent In computing, a user agent is any software, acting on behalf of a user, which "retrieves, renders and facilitates end-user interaction with Web content". A user agent is therefore a special kind of software agent. Some prominent examples of us ...
s directly manipulate the states of target
resources Resource refers to all the materials available in our environment which are technologically accessible, economically feasible and culturally sustainable and help us to satisfy our needs and wants. Resources can broadly be classified upon their ...
. The
POST Post or POST commonly refers to: *Mail, the postal system, especially in Commonwealth of Nations countries **An Post, the Irish national postal service **Canada Post, Canadian postal service **Deutsche Post, German postal service ** Iraqi Post, Ir ...
method, on the other hand, is a process operation that has target-resource-specific semantics which typically exceed the scope of CRUD operations.


User Interface

CRUD is also relevant at the user interface level of most applications. For example, in address book software, the basic storage unit is an individual ''contact entry''. As a bare minimum, the software must allow the user to: * ''Create'', or add new entries * ''Read'', retrieve, search, or view existing entries * ''Update'', or edit existing entries * ''Delete'', deactivate, or remove existing entries Because these operations are so fundamental, they are often documented and described under one comprehensive heading such as "contact management" or "document management" in general.


Other variations

Other variations of CRUD include: * ABCD (add, browse, change, delete) * CRUDL (create, read, update, delete, list) *BREAD (browse, read, edit, add, delete) * DAVE (delete, add, view, edit) * CRAP (create, replicate, append, process)


See also

* Representational state transfer (REST) *
Active record pattern In software engineering, the active record pattern is an architectural pattern. It is found in software that stores in-memory object data in relational databases. It was named by Martin Fowler in his 2003 book ''Patterns of Enterprise Application ...
*
Data manipulation language A data manipulation language (DML) is a computer programming language used for adding (inserting), deleting, and modifying (updating) data in a database. A DML is often a sublanguage of a broader database language such as SQL, with the DML compr ...
*
Input/output In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...
*
ACID In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
*
Query by Example Query by Example (QBE) is a database query language for relational databases. It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL. It is the first graphical query language, using visual ...
* Command–query separation *
Scaffold (programming) Scaffolding, as used in computing, refers to one of two techniques: The first is a code generation technique related to database access in some model–view–controller frameworks; the second is a project generation technique supported by various ...


References

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