3.5 Other kinds of data
All the data we have had so far in the database has been text or numbers. I have mentioned that another type of data might be dates. Modern databases, however, can store other kinds of data than text, numbers and dates. They can also store graphics, moving pictures and sounds.
Activity 12 (exploratory)
What complications might there be when incorporating pictures, sound clips and moving pictures in a database?
The following three points occur to me:
Files for pictures, sound clips, etc., are often very big. This is not an insuperable problem, but often, rather than incorporate the file in the database, a link to it is incorporated. This is a pointer to where the file might be found.
Users of the database need to be able to view the data. This is not usually a problem if the data is text, numbers or dates, but needs special provision if it is not. Imaging and audio software might need to be incorporated, therefore, in the database software so that users can see graphics or hear sound.
Users of databases need to be able to search for data. With graphics, sound or video files it is usual to store associated descriptive text (or keywords) along with the file so that a search can find it.
A common example of a database that incorporates non-text and non-numerical data is the photograph-album software that comes with many digital cameras. This enables the user to archive their digital photographs, along with textual data, such as title, date, camera settings and so on. On a bigger scale, databases relating to large groups of individuals, such as library users, employees, criminals and so on, increasingly include such non-text items as photographs, vocal recordings, fingerprints and iris scans. These are examples of biometric data, which we shall look at in the next section. Biometric data is used to help identification – photographs being perhaps the most obvious example.
Activity 13 (self-assessment)
What are the two main types of database?
What is an entity?
What is the purpose of a joining table?
Flat databases and relational databases.
An entity is a distinct thing for which we wish to store information.
A joining table is a means of relating entities by relating the records of each table through their keys.