Normal Form (doubt)

Question

Here directly dependency not given. Which normal form it doesnot hold , how to eliminate it? I got here 1:m, or 1:1 dependency. Is it any value to ans this question?

Comments

is it in 1nf ..

eid mid is key .. there is partial dependency

i made few tuples according to given schema (e1 m1 s1),(e1 m2 s2) (e2 m1 s1) (e3 m3 s1)

if something wrong let me know

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no Sonam :)

Answer 1

I AM ALSO GETTING RELATIONSHIP AS 1:M 

AS SPECIALIZATION AS RELATIONSHIP AND EACH EMPLOYEE HAS MANY SPECALIZATION.

 

NOW ABOUT NORMAL FORM I AM THINKING IT IS 3NF NOT BCNF 

 

JUST CREATE TABLE AS

EMPID	SPECIALITY	MANGERID
A	1	C
A	2	B
C	1	C
D	2	M

(EMPID+ SPECIALITY) UNIQUE AS STATEMENT EMPLOYEE CAN HAVE MANY SPECIALITY. 

NOW MANAGER ID IS UNIQUE WITH RESPECT TO SPECIALITY AS EACH MANAGER ONE SPECIALITY.

SO THINK OD EMPID AS A AND SPECIAL AS B , MNGID AS C

SO AB------>C

 AND C-------------> B

SO BY THESE IT IS 3NF BUT NOT BCNF AS C NOT CANDIDATE KEY.

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IF ANYTHING WRONG LET ME KNOW :)

Comments

yepp :P thanku for correction it should be ab----------->c MISTAKENLY WRITE A------->BC

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it is duplicate of https://gateoverflow.in/222788/ace-question-8

one more thing is, with in one table ( relation of a RDBMS ), how you are saying it is 1:1 or M:1 or something else?

1:1 or M:1 or some thing else can be represented between two relations of RDBMS only

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@srestha, @Shaik Masthan  : So as per the FD’S : AB→ C, C→ B we got the relation should be in 3NF but not in BCNF. if this is the answer, then we should have atleast 2 compound keys. but here in this case, we don't have it. only key is AB. Can anyone please explain this? i want to know the reason.

Answer 2

The given relation is:

$emp(empid, speciality, managerid)$

The following functional dependencies hold:

$managerid \to speciality $

$empid,speciality \to managerid$

Thus, we see that (empid, speciality) is the candidate key.

Thus, the relation is in 3NF as the RHS of first dependency is prime attribute while the LHS of the second dependency is the superkey.