Lakhasly

3.The Relational Data Model and Relational Database Constraints The relational model was first introduced by Ted Codd in 1970, and attracted immediate attention due to its simplicity and mathematical foundations.3.1 Relational Model Concepts The relational model represents the database as a collection of relations.The model uses the concept of a mathematical relation, which looks like a table of values as its basic building block.

3. The Relational Data Model and Relational Database Constraints
   The relational model was first introduced by Ted Codd in 1970, and attracted immediate
   attention due to its simplicity and mathematical foundations. The model uses the concept of
   a mathematical relation, which looks like a table of values as its basic building block.
   3.1 Relational Model Concepts
   The relational model represents the database as a collection of relations. Informally, each
   relation looks like a table of values or a “flat” file of records. For example, the database of
   files that was shown in Figure 3.1 and 3.2 is similar to the basic relational model
   representation. When a relation is thought of as a table of values, each row in the table
   represents a collection of related data values. Each row in the table represents a fact that
   typically corresponds to a real world entity or relationship. The table name and column names
   are used to help to interpret the meaning of the values in each row.
   Figure 3.1: An example of a database that stores student records and their grades.
   For example, the first table of Figure 3.2 is called STUDENT because each row represents facts
   about a particular student entity. The column names—Name, Student_number, Class, and
   Major—specify how to interpret the data values in each row, based on the column each value
   is in. All values in a column are of the same data type.