Wednesday February 6, 2008

During the last class we spoke about implementing a user interface, accessing database files and database management software.

What were the database management software we discussed?

Oracle, Informix, Microsoft SQL, Ingres,  Postgres, Access, DB2 etc.

What is a relational database?

A relational database is a collection of organized data in which there are relationships between the various data members.  For instance two tables within a database that relate to each other.  In the example of an academic information systems database you could have one table that holds all location information (street address, town, phone number) that could relate to both the student table and the staff/professor table.

Contributed by Brendan from Wikipedia- A relational database is a database that conforms to the relational model, and refers to a database's data and schema (the database's structure of how that data is arranged).

  Today we are going to be going over student demonstrations .

What are the four database functions?  Add (append) , Delete (purge), Modify (update), Search

Bill's Database Demo

The first thing you need to do when organizing/designing your database application is to sit down and write out what your requirements are.

Terms that are important for database design are

Relational Database- A collection of data items organized and a set of formally described tables from which data can be accessed or reassembled in many different ways without having to reorganize the database tables. (http://searchsqlserver.techtarget.com/sDefinition/0,,sid87_gci212885,00.html)

Tuple-  Is a finite sequence (also known as an "ordered list") of objects, each of a specified type (see record)

Record- row—also called a record or tuple—represents a single, implicitly structured data item in a table

table  A collection of data in defined rows and columns.  We have included an example of a table below from page 289 in the textbook. 

Why should we have more than one table?  

bit- A bit is a binary digit, taking a value of either 0 or 1. For example, the number 10010111 is 8 bits long,
 

byte In computer science a byte (pronounced "bite", IPA: /baɪt/) is a unit of measurement of information storage, most often consisting of eight bits.
 

primary key- In relational database design, a unique key or primary key is a candidate key to uniquely identify each row in a table.

 In an database application you need to have two layers.  The application design layer and the user layer..

We also looked at XML eXtensible Markup Language formats for relational databases

Here is a sample.

In the XML you makeup your own data tags to delimit the fields.  In this example we have the table AUTHORS.   Each record is surrounded by the the tag <author> and ends with the tag </author> indicating the end of the record.   Each column in the record is also surrounded by data tags so the field name is surrounded by <name> to indicate the start of the field and the tag </name> to indicate the end of the field.

<!doctype mydata "http://www.w3.org/mydata">
<mydata>

<authors>
<author>
<name>Robert Roberts</name>
<address>10 Tenth St, Decapolis</address>
<editor>Ella Ellis</editor>
<ms type="blob">ftp://docs/rr-10</ms>
<born>1960/05/26</born>
</author>

<author>
<name>Tom Thomas</name>
<address>2 Second Av, Duo-Duo</address>
<editor>Ella Ellis</editor>
<ms type="blob">ftp://docs/tt-2</ms>
</author>

<author>
<name>Mark Marks</name>
<address>1 Premier, Maintown</address>
<editor>Ella Ellis</editor>
<ms type="blob">ftp://docs/mm-1</ms>
</author>
</authors>

<editors>
<editor>
<name>Ella Ellis</name>
<telephone>7356</telephone>
</editor>
</editors>

</mydata>