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<H2>1.1. What is a database?</H2>
<p>
You can define a database as a collection of data on one topic. It is organised in a way allowing to easily browse the information, make changes or add new items.
</p>
<p>
Look at this diagram for one of the above examples: a simple phone book.
<br><img src="img/01_02_example.png">
<br>A diagram of a phone number database<br><br>
The above picture shows a set of two contacts each of which is presented on a separate card. It appears that such a card can constitute a single line in a table:
</p>
<p>
<table border="1" cellspacing="0" cellpadding="2">
<tr><td colspan="2"><b>Contacts</b></td></tr>
<tr><td><b>Name</b></td><td><b>Tel No.</b></td></tr>
<tr><td>Joan</td><td>699 23 43 12</td></tr>
<tr><td>Adam</td><td>711 19 77 21</td></tr>
</table>
</p>
<p>
<b>Terms and definitions</b>: A single data which constitutes a part of a greater collection can be called a <b>line</b> or more professionally a <b>record</b>. The collection is narmally called a <b>table</b>. Moreover, the most natural name for the table is one describing the data it offers/stores which is <b>Contacts</b>. Furthermore, each line in the table consists of <b>columns</b> often also called <b>fields</b>. In the table <em>Contacts</em> there are two columns (fields): <em>Name</em> and <em>Tel No.</em>.
</p>
<p>
For simple uses a single table can make up a <b>database</b>. Many people consider these two equivalent. As you will see, for real databases we usually need more than one table.
</p>
<p>
To sum up, you have already got a simple database with one table <em>Contacts</em>.
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</p>
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