The file approach to storing data is inefficient, especially for large data sets because it hinders access to information as data is stored in separate files and may even be stored in different formats. Data stored according to the file approach lacks interoperability because a specific application is needed to read the data. Moreover, the file approach can lead to duplication of data as well as outdated information, which occurs when a piece of data is updated in only one file rather than in all the files where it has been stored.
Databases are used to store very large, structured data sets. Databases are tools that allow the user to search through a large quantity of data and retrieve the information most useful to them. They eliminate the problem of data duplication because data storage is centralized. This feature also increases data security because access to the database is controlled by a database management system. Finally, data stored in a database is application independent, and therefore more accessible to users.
For the average user, the difficulty of formulating a syntactically-correct query presents one drawback of relational database technologies.
The general formula of a query in SQL is:
SELECT field(s)
FROM table(s)
WHERE condition(s)
(Lecture Notes, Session 7)
Click here for examples of two SQL queries I created and executed.
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