Database Reference
In-Depth Information
The data-set shown in tabular form in following figure is said to be an unnormalised data
set. This can be seen, if the data-item SubjectName is chosen as the key of this data-set and
underline it to indicate this.
A given cell of the table for the attributes StudentID, StudentName and MarksObt have
multiple values. In above table StudentID, StudentName and MarksObt all repeat with re-
spect to SubjectName. The attributes StudentID, StudentName and MarksObt are clearly
not functionally dependent on the primary key SubjectName. The attributes TeacherID and
TeacherName clearly are. This means that we have to form two tables: one for the func-
tionally dependent attributes, and one for the non-dependent attributes. SubjectName and
StudentID are declared as primary key of this second table Results.
