Data models supported by the DBMS
Minister of Education and Science of the Republic of Kazakhstan
K. Zhubanov Aktobe Regional State University
Faculty of Physics and Mathematics
Department of Computer Science and Information Technologies
ABSTRACT
Theme: Data analysis. Data management
Subject : Data Analysis.Data Management.
Specialty: 6B05401-Математика
Course : 1
Semester: 1
Author: student of group 102MKO Serikbayeva Aizat
Teacher: Doctor PhD, Senior Lecturer
Shangytbayeva G.А.
Aktobe, 20 20
Plan
| 1 | Introduction | 4 |
| 2 | Database. Basic concepts of databases and database management systems | 4-7 |
| 3 | DBMS functions | 7-8 |
| 4 | Data models supported by the DBMS | 8-9 |
| 5 | Areas of application of databases in economics | 9-10 |
| 6 | Principles of operation of the Microsoft Access DBMS | 10-11 |
| 7 | Tables. | 11-12 |
| 8 | Requests. | 12-14 |
| 9 | Conclusion | 14 |
| 10 | References | 15 |
Introduction
To make informed and effective decisions in production activities, in managing the economy, a modern specialist must be able to receive, accumulate, store and process data using computers and communication means, presenting the result in the form of visual documents.
Modern life is unthinkable without effective management. An important category is information processing systems, on which the efficiency of any enterprise or institution largely depends. Such a system should:
· ensure the receipt of general and / or detailed reports on the results of work;
· make it easy to identify trends in the most important indicators;
· ensure receipt of time-critical information without significant delays;
· perform accurate and complete data analysis.
The purpose of this course work is to familiarize yourself with the most popular database management systems, such as Microsoft Access and Microsoft Visual FoxPro, used to process economic information.
Coursework objectives:
- get acquainted with databases and DBMS;
- consider the functions of the DBMS and the field of application of databases in the economy;
- to characterize the principles of the Microsoft Access DBMS and Microsoft Visual FoxPro.
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Database. Basic concepts of databases and database management systems
A database is an organized structure for storing information. Modern databases store not only data, but also information.
This statement can be easily explained if, for example, we consider the database of a large bank. It contains all the necessary information about clients, their addresses, credit history, current account status, financial transactions, etc. In addition to data, the database contains methods and tools that allow each employee to operate only with those data that are within his competence. As a result of the interaction of the data contained in the database with the methods available to specific employees, information is formed that they consume and on the basis of which, within their own competence, they enter and edit data.
The concept of a database management system is closely related to the concept of a database. This is a set of software tools designed to create the structure of a new database, fill it with content, edit content and visualize information. The visualization of database information means the selection of displayed data in accordance with a given criterion, their ordering, design and subsequent delivery to output devices or transmission via communication channels.
There are many different database management systems, hereinafter referred to as "DBMS", such as: IMS, Cetop, Oracle, Clipper, FoxPro, Access. But before starting to study the DBMS, let's consider a few basic concepts.
Data is information systematized and structured in some way.
In this work, only the logical representation of data is considered, i.e. from the point of view of an application programmer and user. From their point of view, data is divided into records, which, in turn, are divided into fields, and between the fields, as well as between records, various links can be established.
Field is the main and minimum data element.
Record - multiple fields.
Relationships are logical relationships between records or fields.
A database is a collection of data that is associated with a specific topic or purpose.
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A database can be defined as a collection of machine-readable and storing data that can be used by one or more users.
Databases can be hierarchical, networked, and relational, depending on the different data models. Only relational databases will be considered below.
DBMS (database management system) is a program that manages data, stores, retrieves, searches, and edits information stored in a database. DBMSs are also subdivided into hierarchical, network and relational, depending on the data they process.
TABLE is a set of records (rows), consisting of separate fields (columns), which store information and constitutes, in fact, the content of the database.
Tables are the main form of presentation of information contained in a database. A form cannot be designed without a table; queries and reports are based on tables.
Database tables can generally handle many more different data types. For example, Microsoft Access databases work with the following data types.
Text is a data type used to store normal, unformatted text of limited size (up to 255 characters).
Numeric is a data type for storing real numbers.
Memo field is a special type of data for storing large amounts of text (up to 65,535 characters). Physically, the text is not stored in the field. It is stored elsewhere in the database, and a pointer to it is stored in the field, but this separation is not always noticeable to the user.
Date / in Time is a data type for storing calendar dates and current time.
Monetary is a data type for storing monetary amounts. Theoretically, it would be possible to use numeric fields to write them, but there are some peculiarities for monetary amounts (for example, related to rounding rules) that make it more convenient to use a special data type, rather than setting a numeric type.
Counter is a special data type for unique (not repeated in the field) natural numbers with automatic increment. Natural use is for sequential numbering of records.
Boolean - a type for storing logical data (can only take two values, for example, Yes or No).
A hyperlink is a special field for storing URL addresses of Internet Web objects. When you click on the link, the browser starts automatically and the object is played in its window.
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The Lookup Wizard is not a special data type. This is an object that can be configured to automate data entry in a field so that you do not enter them manually, but select them from the drop-down list.
When placing a database on a PC that is not on the network, the database is always used in exclusive mode. Even if the database is used by several users, they can only work with it sequentially. However, working on an isolated PC with a small database is now no longer typical for most applications. The database reflects the information model of real software, it grows in volume, therefore, the number of tasks solved with the help of this database increases dramatically and, in accordance with this, the number of applications working with a single database increases. PCs are united into local networks, and the need to distribute applications working with a single database over the network is undeniable.
Parallel access to one database of several users, if it is located on one machine, corresponds to the mode of distributed access to the central database. Such systems are called distributed data processing systems.
If the database is located on several PCs distributed in a network, and multiple users can access it in parallel, then we are dealing with parallel access to distributed databases. Such systems are called distributed database systems.
DBMS functions
A modern database management system should perform the following functions:
- data definitions
The DBMS should allow data definitions (external schemas, conceptual schema, internal schema, as well as all associated mappings) in their original form and transform these definitions into the form of the corresponding objects, i.e. the DBMS should include a language processor component for different data definition languages ...
- data processing
The DBMS must be able to process user requests to select, change or delete the corresponding data in the database or to add new data to the database, that is, the DBMS must include a data processing language processor (DSP) component.
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There are "scheduled" and "non-scheduled" queries.
A scheduled request is a request that is required in advance. The administrator must configure the physical database design to ensure sufficient performance for such queries. It is specific to "operational applications".
An unplanned request is a special request that was not anticipated to be necessary. It is specific to "decision support" applications.
- data security and integrity
The DBMS must control user queries and prevent attempts to violate the security and integrity rules defined by the DBMS.
It is not enough for the users of the information system that the database simply reflects objects of the real world. It is important that such a reflection is unambiguous and consistent.
In order to guarantee the correctness and mutual consistency of data, certain restrictions are imposed on the database, which are called integrity constraints.
- data recovery and duplication
Data recovery and duplication is carried out by the DBMS or the administrator.
- introduction of a data dictionary
A data dictionary is a comprehensive collection of tables or files that is a catalog of all data descriptions. It can also contain information about users, privileges, etc., accessible only to the database administrator. The data dictionary is the central source of information for the DBMS, DBMS of all users.
- performance
The DBMS should perform all the specified functions with the highest possible efficiency.
In general, the purpose of a DBMS is to provide a user interface to the database.
Data models supported by the DBMS
Data models are representations of data and their relationships that describe the concepts of a problematic environment. Data models are used for both conceptual and logical and physical representations of data.
There are at least three data models: hierarchical, network, relational.
The hierarchical data model consists of several records, one of which is defined as the root. An example of a hierarchical model is trees:
Where CLIENT, ORDER, SALES AGENT are records (CLIENT is the root record), NUMBER, SURNAME, FIRST NAME, PATRONALY are the fields of the CLIENT record, the lines show the links.
A tree is a directed graph (a graph is a pair of sets, one of which describes a set of vertices, and the other a set of connections between them) where all vertices, except for the root, are in the head of only one arc, the root is not in the head of any of the arcs and is connected with top of the tree.
Relationships can be defined between records in the hierarchy: “one-to-many”, or “one-to-one”, where the record corresponding to the element “one” of the specified relationship is defined as the original one, and the one corresponding to the element “many” - as generated.
The network data model is similar to a hierarchical one, but it is a more general model, in the sense that there are many-to-many and many-to-one relationships between records, and there is also no root node, that is, any record can be a root ...
Network model:
Where CLIENT, ORDER, SALES AGENT are records, NUMBER, SURNAME, NAME, PATRONALY are the fields of the CLIENT record, the lines show the links.
The relational data model is one of the simplest representations of information and the easiest concept to understand. This model represents data organized in tables, most often two-dimensional. Tables of this kind are called relationships (relations) and each table is a separate file.
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