Relational model Essay
A database is an organized collection of data. The data is typically organized to model aspects of reality in a way that supports processes requiring information. (1) Often abbreviated DB, a database is basically a collection of information organized In such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic falling system. Traditional databases are organized by fields, records, and files.
A field Is a single piece of Information; a record Is one complete set of fields; and a file Is a collection of records. For example, a telephone book Is analogous to a file. It contains a list of records, each of which consists of three fields: name, address, and telephone number. An alternative concept In database design Is known as Hypertext. In a Hypertext database, any object, whether It be a piece of text, a picture, or a film, can be linked any other object.
Hypertext databases are particularly useful for organizing large amounts of disparate information, but they are not designed for numerical analysis. To access information from a database, you need a database management system (DB’S). This s a collection of programs that enables you to enter, organize, and select data in a database. (2) Increasingly, the term database is used as shorthand for database management system. There are many different types of Dobbs, ranging from small systems that run on personal computers to huge systems that run on mainframes.
SQL SQL (Structured Query Language) is a special-purpose programming language designed for managing data held in a relational database management system (READS), or for stream processing in a relational data stream management system (READS). Originally based upon relational algebra and duple relational calculus, SQL insists off data definition language and a data manipulation language. The scope of SQL includes data insert, query, update and delete, schema creation and modification, and data access control.
Although SQL is often described as, and to a great extent is, a declarative language (UGLY), it also includes procedural elements. SQL was one of the first commercial languages for Edgar F. Cod’s relational model, as described in his influential 1970 paper, “A Relational Model of Data for Large Shared Data Banks. “ Despite not entirely adhering to the relational model as described by Cod, it became the most widely used database language. 10] SQL became a standard of the American National Standards Institute (ANSI) In 1986, and of the International Organization for Standardization (ISO) In 1987. 12] Since then, the standard has been revised to Include a larger set of features. Despite the existence of such standards, though, most SQL code Is not completely portable among different database systems without adjustments. SQL Is used to communicate with a database. According to ANSI (American National Standards Institute), it is the standard language for relational database management systems. SQL statements are seed to perform tasks such as update data on a database, or retrieve data from a database.
Some common relational database management systems that use SQL are: systems use SQL, most of them also have their own additional proprietary extensions that are usually only used on their system. However, the standard SQL commands such as “Select”, “Insert”, “Update”, “Delete”, “Create”, and “Drop” can be used to accomplish almost everything that one needs to do with a database. This tutorial will provide you with the instruction on the basics of each of these commands as well as allow you to put them to practice using the SQL Interpreter.