relational model - ορισμός. Τι είναι το relational model
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Τι (ποιος) είναι relational model - ορισμός

DATABASE MODEL
Relational Model; Relational data model; Relational model of database management; Relational database model; Relational attribute
  • Relational model concepts.

relational model         
Relational model         
The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd,.
relational data model         
<database> (Or "relational model") A data model introduced by E.F. Codd in 1970, particularly well suited for business data management. In this model, data are organised in tables. The set of names of the columns is called the "schema" of the table. Here is an example table with the schema (account number, amount) and 3 lines. account number amount -------------- --------- 12343243546456 +30000.00 23149875245824 +2345.33 18479827492874 -123.25 The data can be manipulated using a relational algebra. SQL is a standard language for talking to a database built on the relational model (a "relational database"). ["A relational model for large shared data banks" Communications of ACM 13:6, pp 377-387]. (1998-10-05)

Βικιπαίδεια

Relational model

The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations. A database organized in terms of the relational model is a relational database.

The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries.

Most relational databases use the SQL data definition and query language; these systems implement what can be regarded as an engineering approximation to the relational model. A table in a SQL database schema corresponds to a predicate variable; the contents of a table to a relation; key constraints, other constraints, and SQL queries correspond to predicates. However, SQL databases deviate from the relational model in many details, and Codd fiercely argued against deviations that compromise the original principles.