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Relational Databases

Elsewhere in this website I have talked about flat file databases and the size problems you can have when you need multiple intances of the same thing against a record.  Relational database structures alleviate you of this problem.

If you database is relational you have more than one table as opposed to a flatfile database which only has one table.  Each table is linked by a 'primary key' to another table which holds a 'foreign key'  A primary key is a unique identifier in a particlar field in your table.  There can only be one of each instance within that table  Often this primary key is a number and designated as an auto number.  A Foreign key is a field in another database which directly corresponds to the primary key in another table.  If these two keys are the same they link the records from one table to another.  These tables can only link if the relationship is a one to many.  For example one customer have many orders belonging to it.  If you have many parts to a table such as an order then you require another table which holds the dtials of that order or instance.

The diagram below indicates how the tables may link together.

Diagram to show how tables link together in a relational database structure

Splitting out your data in this way makes the database much more efficient in file size as you are only keeping the information you require and not reserving space for lots of empty cells as a flat file database would.

You can gather all your information together from the tables using queries.

database query showing how tables link togeter

To find out how we can help you build a database of revise one already in action, contact us.


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