GATE Overflow Test Series | Mixed Subjects | Test 3 | Question: 22

Question

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

Answer 1

Here we have a ternary relation. A staff registers $0$ or more clients to a branch. So, we need a separate relation for Staff, Branch and Client and another relation for the "Registers" relation which will have ClientId, StaffId, branchNo. So, totally $4$ relations needed to avoid NULLs and redundancies.

Comments

still NULLs are possible in the relation table in some columns even with 4 tables, we need to have more than 4 to not allow nulls.

like a table for .staff client and and one more for branch and staff so that no Nulls possible. so total of 5 tables needed to avoid nulls.

let me know if I am wrong.

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But then how will Clients get mapped to Branch?
I think those null values can’t be avoided in 4^th table