Databases
There are two main types of databases:
-
Flat file databases – all the data is stored in a single file and the sorting and searching
of reports is done in this single file. This kind of a database is easy to maintain but is suitable for small
amounts of data only.
-
Relational databases – they use a DBMS to link independent files together. Two databases can
have a common field which is used to relate the two files.
A database query function allows you to extract information according to certain conditions or criteria.
The sort, search and logical conditions used in a database are:
- Sort ascending
- Sort descending
- Is equal to (=)
- Is less than (<)
- Is greater than (>)
- Is less than or equal to(<=)
- Is greater than or equal to (>=)
- Is not equal to (<>)
- AND
- OR
- NOT
For example a logic condition AND is used when we need to search for information using two criteria.
Status = Age > 30 years AND Average salary > £6,000
Typical applications of databases:
- Creating and maintaining personal lists (students, customers, patients…)
- List of suppliers to a company
- Library catalogues
- Details of careers available with qualification requirements
- etc.
