What is a database?
This article is devoted to the concept of a database. Various databases are now actively used when working with PCs - personal computers. For brevity, we introduce the accepted abbreviation for the database - DB.
What is a database: definition and functions
When asked what a database is, computer science gives a very clear answer.
A database (DB) is a collectionmaterials that are systematized in such a way that they can be easily found and processed using a PC or other computer (electronic computer). Materials can be understood as anything: articles, various documents, reports, etc.
DB is also called such a set of data that is stored on a PC in accordance with a specific scheme.
There is one more definition: a database is a set of permanent data that is used by various software systems of an organization.
Proceeding from these definitions, it is not difficult to guess,for which you need a database for your PC. Different databases are used to organize and store a large number of similar documents and quick access to them. Remember, when you used to come to a large library, how long did the librarian have to find the book you are interested in? But you can not always even remember if there is some material in the card file. Now this problem is solved. It is enough to open the database of interest on your computer and type the name of interest in the search. Quickly finding and processing the information of interest from the list is the purpose of the database and the programs that operate on different databases. Modern databases and programs, through which they are processed, provide invaluable assistance to people of various professions who are forced to work with large volumes of the same type of information. This is primarily trade workers, librarians, employees of medical institutions, accountants.
What is a relational database
A relational database is a database that isbased on the relational data model. A more precise definition we give, so to speak, from the first mouth. Recall that the relational data model proposed and subsequently implemented by the American mathematician Codd in 1970. And in an article from 1985, he also formulated 12 rules, by which you can determine that the given database is relational. We will quote them here.
- Information rule. All information in the database should be presented only in the form of the values contained in the tables, that is, at the logical level.
- Guaranteed access. Access to each element of the database should be done using the table name of the column name and primary key.
- Support for invalid values. Zero values in the database should be used to represent the missing data and must be different from any numeric characters and a space character.
- Dynamic directory. The description of the database on a logical level is presented in the same form as the main data.
- Comprehensive data sublanguage. In a relational database, there must be a special character language with a clear syntax that supports the various elements of the database itself: processing, data definition, transaction boundaries, and so on.
- Updating views. Makes available all views that can be updated.
- Add, update, and delete. Ability to work with databases during these operations.
- Independence of physical data.
- Independence of logical data.
- Independence of the conditions of integrity. The existence of the possibility of determining the integrity conditions specific to each relational database.
- Independence of distribution. That is, independence from the conditions of a particular user.
- The rule of uniqueness. This is the absence of the possibility of using a low-level language for processing data in a high-level language (in the case of several records at once, for example).