Unit 18 - P1

Databases are collections of data that are well organised, allowing them to be accessed and updated quickly and easily. There are different types of databases, classified by their content; they can be either bibliographic, full-text, statistical or multimedia databases.

The main features of databases are tables that are used to store information, an index to allow users to find the information they want quickly and efficiently, relationships between the tables for organisation, and queries which are used to read and write data into the tables.

There are many different types of data; I have picked out the main ones:

• Text/Alphanumeric – data including text, symbols and numbers. Examples include names, addresses and postcodes.
• Number/Numeric – only data in numeric form. Can be whole numbers, negative numbers and decimals, such as height in centimetres and number of pupils in a class.
• Currency – any data that is related to money; £49.50, $20.99 etc.
• Date/Time – data used to store dates or certain times of day, for example; 11/03/2004 or 07:34.
• Boolean – data that can only have 1 of 2 possible outcomes, such as True/False or Yes/No.
• Image – used to store data in image form.

Some databases have their information split into several, more easily manageable groups, these are called relational databases. These separate tables can then be linked together, creating a relationship. Relational databases reduce data duplication, meaning the database will be smaller than if it was all lumped into a single flat file database.

Electronic databases are far more efficient than their paper-based counterparts; massive amounts of information can be searched in just seconds, whereas it could take hours with a large paper-based database. Electronic databases can be copied and backed up at the press of a button, a paper database would have to be photocopied or possibly even written out again. Another advantage of electronic databases is that they can be spell and grammar checked easily, with a paper database, someone would have to read through all of the information to ensure it was correct, and if errors were found, they would not be as easy to change as they are in an electronic database.

Interfaces are essential for databases; a user interface is how the user will see the database interface. A good interface will allow the user to find the information they require in a short amount of time. Badly designed user interfaces will make it difficult for people to perform even the simplest actions. Good interfaces will allow the user to interact easily with the database. 

Macros are small programs (or pieces of script) that can tell an application a whole range of things it can do and how to go about doing them. They can be attached to a command button, and whenever that button is clicked, the macro will run its set of commands. They are often used as a quick way to open reports or run queries.

Reports are used to summarise and present data in the tables. They usually answers specific questions, such as "How much money did we receive from each customer this year?" A report can be run at any time, and will always reflect the current data in the database.

Forms are sometimes referred to as "data entry screens." They are the interfaces you use to work with your data, and they often contain command buttons that perform various commands. Using forms allow you to control how other users interact with the data in the database. For example, you can create a form that shows only certain fields and allows only certain operations to be performed. This helps protect data and to ensure that the data is entered properly.