Databases. The concept of a database system. Database schema. Data. Hardware and software. Database users

The concept of a database system. Database schema. Data. Hardware and software. Database users

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1. Definition of a database system. What is called a database system?

The database system is a computerized system designed to store information, which is presented in the form of records and may be useful for a given user or organization that exploits it. The database system provides convenient tools for obtaining and modifying the necessary information. The information that is placed in the records is a database.

For example. At some enterprise there is a personnel department. For the personnel department, important is general information about the employees of a certain enterprise, namely:

surname, name and patronymic of the employee;
date of birth of the employee;
address of residence.

For the accounting department, the following information about the employee is important:

surname, name and patronymic;
date of birth;
tariff category.

The organization of work with information about employees is performed by a database system or a database management system.

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2. How are the terms “data” and “information” defined in terms of database theory?

The data in the database is the actual data values that are stored in the database. Information in the database is an explanation of the content or essence of the actual data stored in the database.

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3. How are database systems classified by user count?

There are two types of access to a database of a certain number of users database systems:

single user systems. In single user systems, access to the database can simultaneously have no more than one user;
multi user systems. In a multi-user system, multiple users can access the database simultaneously. For a user, working in a multi-user system is no different from working in a single-user system. In a multi-user system, all the difficulties associated with the general access to database resources are imperceptible to the user.

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4. Multiuser database schema. Main components of the database system

Figure 1 shows a scheme of a multi-user database.

Figure 1. Scheme of a multi-user database

In Figure 1, there are 4 main components of the database system:

data;
hardware;
software;
users.

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5. What does the term “data integration” mean?

Data Integration is the ability to present a database with different data files that:

can be combined with each other. For example, a database that is implemented in several data files, information in which complements one another;
completely or partially turn off the redundancy of information. In this case, the file structure is organized in such a way that there is no need to specify additional clarifying information in one file that is already present in another file.

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6. What does the term “data separability” mean?

Data separability is the ability of different users to access the same data item that is located in the database. In other words, each user can use (have access to) the same data element at his discretion. Users can have concurrent access to the same data item.

The data element can be, for example, information from a specific field of a database table.

Example. Figure 2 shows the Worker table, which contains general information about the employee of a certain institution. The data from the fields Name, Surname, Patronymic can be used in different departments of the institution. These departments can be: the accounting department and the personnel department.

Figure 2. Data from the Worker table can be used by different database users

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7. What databases are called special purpose databases?

A special-purpose database is one that does not support data sharing. In such a database, only one user has access to the same database item. A special-purpose database is also called a personal database.

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8. What are the main categories of devices that can be attributed to the hardware of the database system?

Hardware of databases includes two main categories of devices:

means of ensuring the preservation of information. These tools include a variety of external (secondary) memory volumes (usually disk drives), corresponding input/output devices (drives, connectors for flash media, memory cards, and other devices), device controllers, input/output channels, etc.;
tools supporting the operation of database system software. These tools include a hardware processor in combination with the primary memory.

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9. What software components are included in the database software?

Software database systems include:

Database Management System – DBMS. A Database Management System is also called a Database Manager or a Database Server. A DBMS is a level interconnecting the physical database (actually stored data) and the system user;
utilities for organizing work with the database;
development tools for applications that interact with known databases;
database design tools;
report generators based on data placed in a database;
transaction manager of TP monitor.

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10. Database User Classification

Database users are divided into 3 interrelated groups:

application programmers. These are people who develop software that use a database;
end users who work with the database using special software. Typically, the software or user works with the database using a special query language. The most common database query language is SQL (structured query language);
database administrators. These are the people who provide the necessary technical support for the database. They carry out the creation of a database, organize technical control, carry out actions to ensure the necessary speed and its maintenance.

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