Relational Database

A relational database allows the user to set up data structures that include the relationships between data entities. When an attribute of one entity relates to another entity then a link can be defined. Thus, if the music issue were being implemented in a relational database, membership number would be defined as a link between member and part. When a part record was being examined, the relational database would use this link to allow the user to view data relating to the member who had the part on loan.

A piece of data is only stored ONCE in the database. In a relational database if a members name is needed in two tables it is found in the second table by linking it to the first. This means two things in practice, the database is smaller and thus more efficient. Secondly if the members name changes say due to marriage, then only one piece of data must be changed.  

Instead of files, a relational database is made up of tables. Each line of a table corresponds to a record and each column to a field. The user will define table names and column names and specify link fields to establish relationships between the various tables. Once this has been done the relational database management program will allow the user to manipulate data in several tables at once. The program will use the links to allow access to the different tables. The tables themselves are flat files but the links impose an additional structure on these flat files by defining the relationships between them.

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