It refers to an attribute that is shown in the oval shape box. The student number is shown in this oval shape. This will actually determine the necessary details that are dependent on it and can be derived from it. Primary Key is such an attribute that decides the fate or the completeness of deriving the solution linked with the relational database. There could be one or more than one primary database. Primary Keys may not be just the attributes rather the other parameters or the databases have to be entered in them in order to derive the data from it. This is therefore a key or keys that will actually determine the entire relationship in the complete database. This key could be associated with each kind of data or the report that has to be prepared in various ways. This key unless entered will not revealed the other data related with the student data.
These are said to be the keys that help in developing relationships among the various kinds of tables or the data that are presented. For example say in the student relational database in case any student information has to be found out based on the course in which he or they are. In this case the foreign key would actually be creation of the relationship between the student id’s and the course in which they have been studying in the university. This key will surely help in establishing the data among the various entities and the parameters that are linked with the student details of the Northampton School of Business.
In the case where student attendance has to be mapped, the student id or the name could be used as a primary key whereas the course could be related as a foreign key with that of the course in which they have been studying in the university. Based on the reports that would be generated from the various entities, the business decisions could be taken by the school management.