What is a relational model?

Answer 1

A relational model is the means of ordering elements that relates to one another, called a tuple.

Multiple tuples of similar structure can be seen as a table, with rows that describe each tuple, and similar elements ordered in columns.

All operation are described as binary operation as in calculus, e.g. "Insert" is the same as addition, as a new relation is added, where the elements in the relation constitutes a new unique group of values.

Any tuple can have a relation to another tuple - such as "they belong together" or "one comes after the other".

That relations can be represented as tables is used by a number of application building tools, such as MS Access. These refer to the similar elements - the column by assigning them names. They will usually also assume a similar datatype (int, numeric text, float, code, text, etc). The relation model is entirely based on mathematics, relational calculus and relational algebra developed by Chris Data and Ted Codd at Watson Height, IBM Research Center.

The relational model does not relate to any relationship between the tables, and relationships needs to be coded by the application programmer that use codes to make e.g. a parent relates to child. The database system can implement constraints such as that every child has a parent, while not every person has a child.

The model is then used by application developers to create the user interface.

The competing model is the CODASYL network model that was made to satisfy the requirements for application support. This will provide "pointers" that can link a child to a parent, and an order line to a order. However, these does not lend themselves to allow generic tools such MS Access to make the applications, as it does not support the flexibility needed to "just make it".