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.
