A Relational Model

Welcome to this segment on ‘A Relational Model’. In this segment, you will understand the concept of a relational model and the characteristics of a table in it.

A Relational Model

A relational model stores data in the form of tables; these tables are called relations. A relational model is based on the fact that tables are related to each other.

Every table in a relational model has the following characteristics:

1. In a relational model database, the name of every table must be unique.
2. The name of every attribute of a table must be unique to that table.
3. Every table must have a key attribute. The value of this key attribute cannot be the same for any two rows of that table.
4. The data type for each attribute must be defined.
5. The order of the rows does not matter in relation.
6. The order of the attributes does not matter in relation.

Every row or a tuple in a table represents one data record — information about one particular type of entity. Consider Product as a table.

1. Product name and Product Brand as columns.
2. One row in this table will represent one product each.
3. Columns contain the value of each product’s properties.

A relational model is a more detailed implementation of the E-R model. E-R models identify real-world objects, finds properties relevant to business requirements and identify a relation between these real-world objects.

The E-R model is more of a design that is built to understand the business requirements and data the business wants to store. A relational model is more detailed in how actually the schema will be implemented in a system. An entity becomes a table, an attribute becomes a column and the relations are established using foreign keys.