Database Database Access

DBMS is an abbreviation that stands for how it is used for multi-user work with databases, which, in turn, help to store, systematize, classify and control information. Database management systems are divided into types based on the types of data models that they support. The relational view is most practical, since such systems are easy to use and provide many opportunities for developers. This includes, among others, Access DBMS.subd access

General information

The relational DBMS Microsoft Access works, respectively, with relational databases. In general terms, this means a set of interrelated tables, each of which contains data of its own type.

MS Access DBMS is included in the Microsoft Office software.

Capabilities

Access DBMS provides the user with the following features:

  • create databases;

  • add new information to the created database;

  • update or otherwise modify the data in the database;

  • delete existing information from the database;

  • view data in the form of reports, forms, various samples and queries;

  • data organization by sorting and / or classifying information;

  • sharing tables and data when using reports, emails, the Internet and / or local network;

  • the implementation of different types of relationships between tables;

  • creation of button forms and user interfaces for managing the database within the database.

Structural elements of the databasesub ms access

Each database table has rows that include data about objects, as well as columns whose task is to determine their characteristics. Another name for strings is records consisting of fields that are filled with data. The field must have a data type (numeric, text, date, Memo, etc.). All entries in the table contain equally defined, but differently filled in information fields.

Field properties

Fields in the MS Access DBMS define the database structure, as well as set properties for data from the record cells.

The main properties are:

  • Field nameUsually they set headings to columns, that is, they call the characteristic of the object. Also, by the field name, it can be accessed for information when performing automatic operations with the database.

  • Data typeSets the corresponding property, determines which type can be written to the cell.

  • The size.Sets the maximum length of the recorded data.This property is not necessary to use, although it simplifies the work by imposing restrictions on the database user.

  • Format.Formats data fields.

  • Signature.Performs the same function as the name - heading the feature. If the signature is not specified, the title will be the first paragraph. The second possibility of the Name - an appeal to it from the database - the signature does not have.

  • Obligatory field.If you tick the box next to this property, you will not be able to leave the cell blank. For key fields, this property is enabled by default.

Data typesdatabase subd access

Database fields in Microsoft Access can have data types such as:

  • Text. The easiest type of field. Despite the name, it may contain both letters and numbers, symbols and so on. Therefore, it has limitations only in length - no more than 255 characters. It is convenient to use if no further calculations are required between cells, therefore, if only numbers are entered in the field, it is better to use the corresponding type.

  • Memo field.The same text type that stores large amounts of information (up to 64 KB, that is, up to 64 thousand characters). Because of this characteristic, MEMO cannot be used as a key or index.

  • Numerical. Digital field with subtypes, the choice of which depends on the desired accuracy of calculations, etc. Up to 8 bytes or 16 for replication codes.

  • Counter. A field that does not need to be filled in - values ​​(numbers in ascending order) are automatically entered into a table, allowing the data in the cells to remain unique. Simply put, the counter numbers the records in the database. It is convenient to use as a key 4 bytes, 16 - for replication codes.

  • Logical. Used only for the value - 0 (no) and minus 1 (yes). You can configure different recording options - check mark or manual selection (size - 1 byte).

  • Date Time.The name of the data type speaks for itself. Data can be output in seven different formats. 8 bytes.

  • Monetary.Defines currency values. This data type appeared to prevent rounding in calculations. Also 8 bytes.

  • OLE object field.Accepts objects of different formats - graphics, audio, etc. Size - up to one gigabyte.

  • Hyperlink.Addresses of Internet pages, sites. Up to 64 thousand characters.

  • Substitution wizard.In advance assumes the bound tables. Allows you to select a value from another table or from a combo box. The type of the selected value is automatically set. Has a primary key size. No more than 4 bytes.

Keys

MS Access databases in MS Access have one main thing in the tables - the key - the field. By default, it is, as already mentioned, a must-fill. In addition, it imposes the need to be unique, which means that the value already entered in the key field cannot be entered in the key field of another entry in the same table. If necessary, you can add an additional key field, with less stringent rules - the uniqueness is chosen by the database developer. With the help of key fields make connections between database tables.subd microsoft access

Keys are divided into:

  • primary (main) - directly the connection itself;

  • secondary (external) - a method of communication.

Table links

Database Database Access can contain tables that interact with each other. For this purpose, links that are of the following types are used:

  • One to one.This means that each record from the first linked table corresponds to one record from the second.

  • One to many.Each entry from the first table corresponds to a few (two or more) from the second.

  • Many to one.Many records from the first table are associated with one of the second.

  • Many to many.The set of records of the first table corresponds to the set of the second.subd access objects

Name Restrictions

Microsoft Access places restrictions on the names of fields and controls, they also affect Access database objects:

  • the name must not contain more than 64 characters;

  • do not use a period, exclamation mark, superscript character or square brackets;

  • the name cannot begin with a space;

  • control characters cannot be used in the name (codes from 0 to 31 in ASCII);

  • The name cannot include direct quotes.

Objects

Objects of MS Access are a user interface of the database. It allows you to directly manage it and its data.

Tables

The main object, which has already been mentioned many times in this article. They define the structure of the entire database. They store data that can be changed, deleted or added. Tables can be interconnected. On the basis of this object, all the others are built, with the help of them the basic operations with data are carried out.

Requests

objects ms access

Allow to process data from tables. A query can be a selection of some feature from one or several tables. You can also sort or filter information, analyze data, extract and present it to the user in a convenient way.The result of the query is a temporary new table.

Forms

Used as a means to enter new information in the table. The advantage of forms is their user-friendly look - the developer can use the form layout or create a completely new one. On this object you can put buttons, switches and more. Among others, special attention attracts to itself the button form, which is a modified task manager, compiled by the user "for themselves." On it you can put the main functions of working with the database - input, output, filling in tables, viewing data. Conventional forms can also be included in the button.creating subd access

Reports

Represent the end result. Designed for subsequent printing, because they have the appropriate formatting. Allow you to make selections and groupings. Clearly reflect the information embedded in the database.

Access database technology

Development of the database in Access is performed using the following points:

  • Determine the purpose of database development It is necessary to determine the purpose, find out which direction to go - how they intend to use the database, what results they want to get, what functions should be implemented.

  • Determine the approximate number of tables in the database - the information needs to be systematized and “decomposed”. Do not add too many fields in one table: it’s better to split the data into two and link them. Each table should contain only one topic.

  • Define all fields and their data types in tables. The data in the cells must correspond to the types, so that later there will be no problems with calculations, grouping and sorting.

  • Determine the ratios of the table-field.

  • Mark the primary and (if necessary) secondary keys in the tables.

  • Build a data schema for the database, reflecting the relationships between the tables. Maximize the interaction between data using these links.

  • Improve the structure by visually looking at all the available information and its possible systematization.

  • Use the analysis of Access itself for the next check.

Creating a database in Access is possible in two ways:

  • use the database wizard to create the necessary objects;

  • create an empty database, complementing it with new objects yourself.

MS Access allows you to expand the database after it has been created, but the basic structure needs to be thought out in advance: things like data types, later, especially after filling in the table, will not be possible to change.

A well-designed data scheme can be implemented using the appropriate tab in the DBMS. Each type of connection is clearly shown in Access. Links can be modified or even deleted.

Related news

Database Database Access image, picture, imagery


Database Database Access 56


Database Database Access 19


Database Database Access 23


Database Database Access 35


Database Database Access 6


Database Database Access 93


Database Database Access 61


Database Database Access 78