To achieve the first normal form the primary key focus is changed in order to discriminate repeated groups. Fr example for the following un-normalized entity the focus is on the Dept# as a primary key. T achieve second normal form full functional dependencies are to be observed. Atributes that are not fully dependant are isolated as another entity with the respective primary key. Fr example for the above mentioned entity, Wile there are significant non key attributes that are fully dependent on “Department” entity, terefore to achieve second a new entity namely department is introduced with its respective primary key and dependent attributes.
Te two entities namely Student and Course are linked to each other in a many – many relationship. 0highlights the respective relationship. Astudent can take multiple courses while a course can be taken by multiple students. Hwever it is possible that a course is not opted by any student. O the other side a student must opt for at least a course to maintain the status of a student. Te process of registration explains between these two entities to a greater extent.
1highlights that a student gets registered with a course and a course is offered to students for registration. Smilarly the relationship between section and courses exists in the same manner. Mltiple courses are taught in a section while a course may be taught in multiple sections. Te respective elaborated ER diagram is presented in Figure 2. Te relationship of students with their department and their section are of same type i. oe – many. Adepartment or a section may have students a student may get associated with a single section or department at a time.
Hwever for a section to exist at least one student is required to study into it while there is no such restriction for the existence of a department. Te relationship between Student and Grade Report will always be one – one. I general there will always be one grade report for each student but this case is a bit tricky. I the grades are recorded course wise or semester wise the there may multiple records the id of each student.
Tis is done in order to allow gradual updates. Te fact is that whenever a student’s marks report is queried there will be just one up to date consolidated report. 3highlights the E – R model. Te entities “Instructor” and “Section” are linked in a many – many. ..
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