In the seventies and eighties, when computer scientists still wore brown tuxedo jackets and glasses with large, square frames, data were often stored in flat files. Flat files are text documents in which data are seperated by (usually) comma's or tabs.
What IT pro's looked like in the seventies. (The one in the lower left corner is Bill Gates)
Flat files are still in use today for the representation of simple lists of data. The Comma Seperated Values (CSV) format is very popular and widely supported by different software and operating systems. Microsoft Excel is one popular application that can handle CSV files. The data contained in a flat file can be read by a computer program.
Above is an example of what a flat file could look like. A program reading this flat file would have to be told that the data are separated by comma's. If it wanted to select the category that the 'Database Design Tutorial' is in, it would have to read the file line by line until it found the words 'Database Design Tutorial' and then it would have to read the next word after the comma to find the Software category.
Reading a flat file line by line is not very efficient. In a relational database data are stored in tables. The database table below contains the same data as the flat file. Each row or "record" contains one tutorial. Each column represents a property of the tutorial, in this case its title and its category.
A computer program could search the tutorial_id column of this table for a specific tutorial_id to quickly find the corresponding title and category. This is much faster than going over all the data line by line, like a computer program would do in a flat file.
Modern relational database are designed to enable advanced data selections from specific rows, columns and from multiple tables at once at very high speeds.
History of the relational model
The relational database model was invented in the seventies by Ted Codd, a British computer scientist. He wanted his model to overcome the shortcomings of the network database model and the hierarchical database model. He succeeded very well. The relational database model is now widely adopted and considered a powerful model for the efficient organisation of data.
Today, a wide range of relational database products are available, ranging from light-weight desktop applications to feature-packed server systems with highly optimized retrieval methods. Some of the best known Relational Database Management Systems (RDBMS) are listed below.
- Oracle. Mainly used for professional, large applications
- Microsoft SQL server. Microsofts' professional RDMS. MSSQL is available only for the Windows operating system.
- Mysql. Mysql is a very popular open source relational database system. Mysql is widely used in the open source community by both beginners and professionals worldwide. What's more, Mysql is available for free.
- IBM has a range of database system, from which DB2 is the best known.
- Microsoft Access is a RDBMS that is used in the office and at home. Microsoft Access is really more than a database. It is a tool that allows you to build a complete database application with a user interface.
On the next page of this database design tutorial you will learn about some of the the characteristics of relational databases.