What is a relational model?

The

relational model is a simple, yet concise storage frame for databases, and since 2011, it has been the most widely used database frame in the last 40 years. The first actual use of the database model was in 1969, when its founder, Dr. Edgar F. Codd, wrote a report for his IBM employer and used the basic structure of the relational model to develop his report. The message was received with astonishment. Dr. CODD was immediately allowed to fully develop not only the basic structure, but also an operation of what was to become a relational model for databases. On a relational model for use in questioning data in relational databases based on a language of queries, a structured language of queries (SQL) was built.

All programmers and programs developers are educated in concepts and operations of a relational model and can program around its structure. The relational model uses predominantThe fact logic of the declarative method A is based on mathematical terms of two -way logic true and false, all data related to this logic are subsequently operated by relational and relational algebra. These mathematical operations cause data not only to easily inquire from data, but also easily update with a few steps when adding an order to the table. The use of variables to quantify information using the relational model values ​​also uses specific keys to apply restrictions to use and interviewing information. From the beginning he used Dr. CODD attributes to data specification and consistency was built into a relational model that encouraged it to become the most widespread database management tool.

In operation, information in the relational model database is divided into small components permissible for restructuring in many ways to create larger images, depending on the variables in relation to data and lineings many smaller components in relation to each other. These smallThe components are called entities and are organized in the columns and rows table. Information can be entered using any format and is stored on the basis of a set of logical rules after the designated proposal principles. Unique keys identify entities and maintain reference integrity, and therefore the question always finds the same result as there is no duplication of information. Since this structure makes a relational database so flexible, programmers can write for a database to access multiple diverse applications.

Many commercial and open source products have been built on a relational model since the late 1960s, and most of them use SQL inquiry to match predicate logical components in a relational database. Although it is not necessary to use all SQL functions that are capable of logic of three values, it can still ask a relational database. There are at least 30 -language languages ​​than SQL that are capable of managing databases and interviewing a relational database. SQL was only the first language pEsited with developed initial relational model database.