GATE Overflow Test Series | Mixed Subjects | Test 3 | Question: 21

Question

The numbers of relations required when the below ER diagram is converted to Relational model is ________

 

Answer 1

This is a one-one relationship with partial participation on one side. Here, any staff manages zero or one branch. So, we can have a relation each for Staff and Branch and then include the Managing StaffNo in the Branch relation. Thus, only $2$ relations are required and we have no NULLs and no redundancies.

Comments

@gatecse sir. In the question it says one of the entity is having total participation in the one to one relationship, so one relationship table will be enough. I completely agree with your point that several NULL values will appear but most of the questions I have seen demands for a minimum number of tables and in the answer they consider NULL values. As given in the reference of this geeks for geeks page. So I am really confused which one to go for if the question is asked in the exam.

https://www.geeksforgeeks.org/minimization-of-er-diagrams/

https://gateoverflow.in/143588/minimum-number-of-tables-to-represent-er-diagram