DBMS Finding the Super Keys involving normalization concept

Question

Consider an entity employee with attributes (EmpID, Empname, Deptname, Salary, mobno, Project ID, Designation) No two employee with same name and No two employee with same ID. An employee can have more than 1 mobileno and can work on one project only. A relation is designed satisfying the requirement of 2NF. The number of super keys there in the table containing attribute project ID are __________.

Comments

48 ?

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how ??

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2 candidate keys are there. Total 6 attributes in the table. Total superkeys will be : $2^5 + 2^5 - 2^4$ = 48

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It is mentioned “An employee can have more than 1 mobileno and can work on one project only. A relation is designed satisfying the requirement of 2NF.”. but we haven’t used anywhere in the solution. Can anyone plz provide the detailed solution. covering all the points mentioned in Question text.

Answer 1

There r total 7 attributes first seperate Project ID now we have 6 attributes 
now we have 2 candidate keys EmpID, Empname as given in question
  super keys using EmpID =2⁵=32
 super keys using Empname 2⁵=32
repeated superkeys =2⁴ =16
 so by using principle of enclusion-exclusion 
n(EmpID U Empname)=32+32-16=48
now add Project ID to all these 48 
ans =48

Comments

the statement "A relation is designed satisfying the requirement of 2NF. " where it has used as given .

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As per given information we have 2 nontrivial dependency one for EmpID nd other for Empname
nd both r super key (every cand key is also super key) so it is in bcnf hence it is in 2NF also...

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Can you please let me know the source of your understanding? I mean this explanation is great but it didn't occur naturally to me.

 

And also it's mentioned that phone number is multi-valued, shouldn't we do anything about that?