P5/M3

P1 update

What Is A Database?
A database is a structured collection of data that is organized in a certain structure so it can be easily accessed.    You do this by using tables which consist of columns and rows where different data types are stored. Databases can be classified according to types of content: bibliographic, full-text, numeric, and images.

Main features of a database;
- Tables
- relationships
- Data entry forms

Data Types;

- Text/Alphanumeric: This is simply known as text. It also consists of symbols and numbers and is used for all software.  

Numeric Data:

- Numeric data consists of numbers. It can also have decimals, fractions and positive and negative numbers.

Date/Time:

Is simply just date and time.

Boolean:

Boolean date can only consist of two values, Yes/No True/False On/Off 

Database Relationships

• One-to-many and many-to-one relationships 
• An employee can work in only one department; this relationship is single-valued for employees. On the other hand, one department can have many employees; this relationship is multi-valued for departments. The relationship between employees (single-valued) and departments (multi-valued) is a one-to-many relationship. 
• Many-to-many relationships 
• A relationship that is multi-valued in both directions is a many-to-many relationship. An employee can work on more than one project, and a project can have more than one employee. 
• One-to-one relationships 
• One-to-one relationships are single-valued in both directions.

Electronic and Paper Databases

A paper based system can only be used in one way which cannot be easily searched, modified, or accessed. A lot of written databases are now being put on computerized systems as it is more efficient but takes a lot of effort. 

Electronic databases are a lot easier to handle than a paper based database as it eliminates all of the problems a paper database has. An electronic database has it's advantages and disadvantages, If a document on a computer is erased it is automatically put into the recycle bin therefore it is never really deleted. A disadvantage would be if a database was put on a memory stick and was not saved correctly and the stick was lost that database would be gone forever.   

Interfaces
These are tools that are used by a software engineer, developers and programmers which are the middle man of components. Forms, reports and switchboards are the interfaces used inside a database and help to organize and communicate with the data base as the forms are used to log in information.

Report
A report is used when data form a database is summarised and presented so it is easy to read. A question would be put into the database like "how much profit did we make in july?" and the answer would apear in a structured form. 

Forms
A form is an interface that someone uses to create a database. It has a wide range of different command buttons that perform to certain demands. The button can be designed to how to user wants and which information is displayed on the form.

Switchboards

This acts as a menu button which enables standard commands to be run. for example if a button called "films" is pressed then all the films should appear in a form.

P7 (CORRECTED)