chapter 1 - basic database

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Chapter 1Database Basics

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What is a database?

A database is a repository of information.

Primarily concerned with r elational databases the most

commonly used type of database in the world today

A RELATIONAL database

Stores data in tables which comprise rows and columns.

Enables you to retrieve or query  subsets of data from tab

Enables you to connect tables together for the purpose o

retrieving related data stored in different tables.

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What Is a Database Engine

The basic functions of a database are provided by a data

engine a software system that manages how data is stor

and retrieved.

The database engine covered in this subject is called Micro

Jet.

Jet isnt a commercial product; rather it is a subsystem tha

several Microsoft products use.

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What is a table?

Database comprise tables which in turn comprise record

which in turn comprise fields.

A table is a way of storing data that organizes information

a database.

Tables have a predefined structure; they contain data that

into this structure.

Tables organize information in rows and columns.

Within a table a row of data is called a r ecor d whereas col

of data are referred to as fields.

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What is a table?

A record represents a particular element of data such as a

persons entry in an address book or a single banking

transaction.

A field meanwhile represents a subdivision of data in a rec

A record that represents an entry in an address book migh

consist of fields for first and last name address city state zi

and telephone number.

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What Is a Recordset?

A r ecor dset is a data construct provided by the Jet datab

engine. It is conceptually similar to a table but includes s

important distinctive properties of its own.

When you work with recordsets in the Jet database eng

each recordset is represented as an object conceptually

similar to the user-interface objects (such as command

buttons and text boxes) that you might have worked wit

Visual Basic in the past.

Just like other types of Visual Basic objects recordset ob

have their own properties and methods.

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R 

E  C  OR D S E T 

T Y P E  S 

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What are data types?

Visual Basic is a w eakl y t yped language which means tha

arent usually required to declare the data types of the

variables you work with as you would have to do in a st r

t yped language.

If you choose not to type your variables explicitly they si

default to the Variant data type which is an easy metho

use.

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Creating a Database Schem

Although creating a list of tables and fields is a good way

nail down the structure of the database you will also wa

way to look at the tables and fields in a graphical format

Then you not only can see which tables and fields are av

to you but also how they relate to each other.

To do this you create a schema.

A schema is a road map to your database.

The schema diagrams all the tables fields and relationshipyour database

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T  o

 b  e c  on

 t  i  n u e d 

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