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As a rule, the database exists independently of individual programs... Separating data from programs allows different programs to use the same data for their own purposes. The ideological value of databases is explained by the fact that they are based on the concept of an information data model, that is, some abstraction of data presentation. The information in the database is organized in different ways. Three main structures of data representation in the database can be distinguished: hierarchical (tree-like); network relational (tabular).

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Structures for representing data in a database Hierarchical Relational Network In most cases, relational databases are used, in which data is presented in the form of linked files consisting of records. The structure of all records in files is the same, and the number of records in a file is variable. The data items that make up each record are called fields. One record contains information about one object of the real system, the model of which is presented in the table. Record 1 Record 2

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Fields are various characteristics(attributes) of the object. Field values ​​refer to one object. Since all records have the same fields (with different meanings), it is convenient to give the fields unique names... The records differ in the meaning of the keys. The main key in the database is called a field (a set of fields), the value of which is not repeated for different records. Very often, the record number in order is used as the master key. There is one very important property associated with each field - the type of the field. The type defines the set of values ​​that a given field can take in various records. The type of value determines the actions that can be performed with it. Relational databases use four main types of fields: numeric (integer and real), character, date, and logical.

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Example 1. Describe the structure of the "TV program for a week" database In the table, for the "Channel" field, an integer numeric type is used, and for the "Time" field - a real one.

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By itself, the database cannot serve user requests for information search and processing. A database is just a "warehouse" in which information is stored. The role of "storekeeper" in this warehouse is performed by special software systems, which are called database management systems (DBMS). All DBMS support, in one form or another, four basic operations: add one or more records to the database; delete one or more records from the database; find one or more records in the database that satisfy a given condition; update the value of some fields in the database.

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Most of the DBMS support, in addition, the mechanism of links between the various files included in the database. For example, a link can be established explicitly when the value of some fields is a link to another file, such DBMS are called network, or the link can be established implicitly, for example, by the coincidence of field values ​​in various files... Such DBMS are called relational. A relational database makes it easy to find, analyze, maintain, and protect your data because it is stored in one place. MS Access is a functionally complete relational DBMS, in which all the tools and capabilities typical of modern DBMSs are reasonably balanced.

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Self-check questions What is a database? What data storage structure is used in the database? What is so special about a relational database? What is the convenience of tabular presentation of information? How is the data structure described in a relational database? What is a record, a record field? What information do they contain? Define the following concepts: field name, field value, field type. What are the types of fields? What is a DBMS? What is the purpose of this species software? What DBMS are called relational? What are the main functions of a DBMS? What type is Access DBMS?

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Database management system Microsoft ACCESS Completed by: A.A. Pavlova Gr. 331-LD Checked by: G.A. Tunakova Presentation

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Access DBMS Objects Tables are the basic objects of any database. The tables store: all data available in the database, the structure of the database (fields, their types and properties). Object (bookmark) of the table Methods of creation

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Access DBMS objects Queries are objects used to retrieve data from tables and present them to the user in a convenient form. Queries are used to perform operations such as selecting data according to a given criterion, sorting and filtering them. Using queries, you can transform data according to a given algorithm, create new tables, automatically fill tables with data imported from other sources, perform simple calculations on tables, and much more. Object (bookmark) requests

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Access Database Management Objects Forms are tools for entering data or viewing data. Provide the user with the means to fill in only those fields that he is supposed to fill out. At the same time, special controls (counters, drop-down lists, radio buttons, check boxes, etc.) can be placed in the form to automate input. Forms tab

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Access DBMS objects Reports are designed to output data to a printing device (for example, a printer). They have taken special measures to group the output data and to display special design elements typical for printed documents (header and footer, page numbers, service information about the time of report creation, etc.). Macros automate the execution of a specific database operation without programming. Modules contain programs in the Visual Basic language used to customize, design and expand the database. Access pages are designed to view and work over the Internet with data stored in MS Access or MS SQL Server databases.

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Microsoft Access Data Types Text is a data type used to store regular, unformatted text of limited size (up to 255 characters). Memo field is a special data type 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. Numeric is a data type for storing real numbers. Date / Time is a data type for storing calendar dates and current time.

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Microsoft Access Data Types 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 repeating 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).

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Microsoft Access Data Types Field OLE object- A special data type for storing objects, such as multimedia, inserted by embedding or linking (OLE). In reality, of course, such objects are not stored in the table. As with MEMO fields, they are stored elsewhere internal structure the database file, and the table only stores pointers to them (otherwise, working with tables would be extremely slow). A hyperlink is a special field for storing URL addresses of Internet Web objects. Clicking on the link automatically launches the browser and displays the object in its window. The Lookup Wizard is not a special data type. This is an object that can be configured to automate data entry in the field so that you do not enter them manually, but select from the drop-down list.

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Tools for creating database objects Microsoft Access DBMS Microsoft Access DBMS provides several tools for creating basic objects: manual - developing objects in the Design mode; automated - development with the help of wizards; automatic - means of accelerated development of the simplest objects.

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Tools for creating database objects Microsoft Access DBMS Recommendations for using the tools for creating objects: When developing training tables and queries, it is recommended to use manual tools - to work in Design mode. Using the wizards will speed up your work, but will not help you master concepts and techniques. When designing training forms, reports, and access pages, it is best to use the automated tools provided by the wizards. The design of these objects is time consuming, so it is better to entrust it to the program, and the student to focus on the content of the work.

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Creating the structure of the database tables In the database window, select the Tables object Select the Create table item in design mode In the design window, specify the field name and data type Define the primary key of the table

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Establishing links between tables Menu Tools - Data Scheme Add tables participating in links and close the Add window Drag the field of the Student table to the corresponding field of the Book table.

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MS Office Access interface

Microsoft Office Access 2010

A database in Access is a collection of all tables, queries, forms, reports, macros, and modules that make up a complete system.

Database objects - tables, queries, forms, reports, macros and modules. In addition, Access contains several other objects, including links, database properties, and import and export specifications.

You can use Access to manage all of your data in one file. You can use the following elements in an Access database file:

tables for storing data;

queries to search and retrieve only the necessary data;

forms for viewing, adding and changing data in tables;

reports to analyze and print data in a specific format.

Microsoft Access database files

Report Form

Microsoft Access database files

1. Data is stored once in the same table, but viewed from different locations. When data changes, they are automatically updated wherever they appear.

4. Display and print of data is carried out using a report.

Tables and relationships

Table - data storage; this is the starting point for building your application. Regardless of whether the data is stored in an Access database or the application refers to it by linking external tables, everything else Access objects refer directly or indirectly to tables.

Inquiries

A query helps you find and retrieve data that matches specified conditions, including data from multiple tables. The query can also be used to update or delete multiple records at the same time and to perform prescribed or custom calculations based on the data.

• Definition of the program;
• Purpose and functions;
• Objects;
• Data types;
• Program menu;
• Methods for creating objects;
• Examples of objects.

Relational DBMS are the most widely used on modern personal computers. ACCESS.

Application Microsoft Access Is a desktop relational database management system ( DBMS), designed to work on an autonomous personal computer(PC) or local computer network operated by a family of operating theaters Microsoft systems Windows).

Microsoft Access DBMS possesses powerful, convenient and flexible means of visual design of objects with the help of Wizards, which allows the user with minimal preliminary preparation quite quickly create a full-fledged information system at the level of tables, queries, forms and reports.

Databases have the extension  .mdb.

MAIN OBJECTS OF THE DB

table – an object designed to store data in the form of records and fields.

The form – an object designed to facilitate data entry.

Inquiry – an object that allows you to get the required data from one or more tables.

Report – an object for printing data.

ANY TABLE CAN BE PRESENTED IN TWO MODES:

In the mode tables, intended for data entry, viewing and editing.

In the mode constructor , designed to create the structure of the table, change the data type, change the structure of the table (add and remove fields).

ORGANIZATION OF WORK WITH TABLES

table- the main (base) database object. All other objects are created based on existing tables.

• V tables all data available in the database is stored; And tables
• V tables all data available in the database is stored;
• And tables store the structure of the database (fields, their types and properties)

There are the following request creation modes:

• In master mode.
• In design mode.

In the mode constructor. A window appears on the screen, new request, which lists all the ways to create a request. It:

• Constructor.
• Simple request.
• Cross query.
• Duplicate entries.
• Records without subordinates.

ORGANIZATION OF WORK WITH INQUIRIES

Inquiry Is a database object that allows you to perform basic data processing operations:

• sorting,
• filtration,
• combining data from different sources,
• data conversion
• save the results with a certain name so that you can use them later as needed.

• The form is the most convenient way to view and enter data.
• The form is created on the basis of already developed tables and can include not only one, but also several related tables.

• Most quick way creation shape- with the help of a wizard.

• The form can have a tabular form, but most often they use a tape - each object has a separate card.

• Report- the ability to create various forms of presentation of output information.

• Convenience of computer reports lies in the fact that they allow you to group information according to specified criteria, enter the total fields for counting records by groups throughout the database.

• Report is a convenient form of information presentation for printing.

DATABASE PROTECTION

Access has the best protection system among all desktop DBMS. The built-in wizard allows you to create groups, users, assign access rights to all objects, including modules. Each user can be provided with an individual password.

The protection system is available both visually and programmatically.

Microsoft Access is the most popular desktop database management system today. Her success is largely due to her inclusion in the family Microsoft Office... This software designed for both beginners and advanced users

Databases: concept, basic elements. A database is an information model that allows you to store data in an orderly manner. Software designed to work with databases is called a database management system (DBMS). In a hierarchical database, records are ordered in a certain sequence, like steps of a ladder, and data retrieval can be carried out by sequential "descent" from step to step. A relational database is a two-dimensional table. Elements of a relational database: Columns of a table are called fields: each field is characterized by its own name and data type (text, number, date, boolean, counter). Table rows are records about an object. A database record is a table row containing a set of values ​​of a certain property, Database classification: By the nature of the stored information: - Factographic (filing cabinets), - Documentary (archives) By the way data is stored: - Centralized (stored on one computer), - Distributed ( used in local and global computer networks). By data organization structure: - Tabular (relational), - Hierarchical,