key field
It's a piece of data in a database that is unique to a particular record.
For example, in a file of all the children in a school, a record would be all the data about a particular pupil. The key field would be Pupil Number which would be a number set up so that each so that each pupil is allocated a different number when they join the school.
This is important so two pieces of extremely similar data do not get mixed up.
flat files
A database which consists of only one table
One advantage is that it is very simple, and easy to view basic information from.
2 disadvantages are:
- There is often a lot of duplicate data in the table.
- When a record is deleted, a lot of data that is still useful may also be deleted.
Relational database
A database which consists of more than one table
2 advantages are:
- The book's details and the customer's details only need to be entered into the database once.
- Because of this, mistakes are less likely to happen and if there were a mistake in a customer's record, for example, correcting it will correct the mistake database-wide.