Microsoft Access has the look and feel of other Microsoft Office products as far as its layout and navigational aspects are concerned, but MS Access is a database and, more specifically, a relational database.
Before MS Access 2007, the file extension was *.mdb, but in MS Access 2007 the extension has been changed to *.accdb extension.
Early versions of Access cannot read accdb extensions but MS Access 2007 and later versions can read and change earlier versions of Access.
An Access desktop database (.accdb or .mdb) is a fully functional RDBMS.
It provides all the data definition, data manipulation, and data control features that you need to manage large volumes of data.
You can use an Access desktop database (.accdb or .mdb) either as a standalone RDBMS on a single workstation or in a shared client/server mode across a network.
A desktop database can also act as the data source for data displayed on webpages on your company intranet.
When you build an application with an Access desktop database, Access is the RDBMS.
Let us now understand what Data Definition is −
In document or a spreadsheet, you generally have complete freedom to define the contents of the document or each cell in the spreadsheet.
In a document, you can include paragraphs of text, a table, a chart, or multiple columns of data displayed with multiple fonts.
In spreadsheet, you can have text data at the top to define a column header for printing or display, and you might have various numeric formats within the same column, depending on the function of the row.
An RDBMS allows you to define the kind of data you have and how the data should be stored.
You can also usually define rules that the RDBMS can use to ensure the integrity of your data.
For example, a validation rule might ensure that the user can’t accidentally store alphabetic characters in a field that should contain a number.
Working with data in RDBMS is very different from working with data in a word processing or spreadsheet program.
In a word processing document, you can include tabular data and perform a limited set of functions on the data in the document.
You can also search for text strings in the original document and, with ActiveX controls, include tables, charts, or pictures from other applications.
In a spreadsheet, some cells contain functions that determine the result you want, and in other cells, you enter the data that provides the source information for the functions.
An RDBMS provides you many ways to work with your data. For example,
You can search a single table for information or request a complex search across several related tables.
You can update a single field or many records with a single command.
You can write programs that use RDBMS commands to fetch data that you want to display and allow the user to update the data.
Access uses the powerful SQL database language to process data in your tables. Using SQL, you can define the set of information that you need to solve a particular problem, including data from perhaps many tables.
Spreadsheets and word processing documents are great for solving single-user problems, but they are difficult to use when more than one person needs to share the data.
When you need to share your information with others, RDBMS gives you the flexibility to allow multiple users to read or update your data.
An RDBMS that is designed to allow data sharing also provides features to ensure that no two people can change the same data at the same time.
The best systems also allow you to group changes (which is also known as transaction) so that either all the changes or none of the changes appear in your data.
You might also want to be sure that no one else can view any part of the order until you have entered all of it.
Because you can share your Access data with other users, you might need to set some restrictions on what various users are allowed to see or update.