er model,databases

Question

IF A RELATION HAS ______________ CARDINALITY, THEN NO MINIMIZATION CAN TAKE PLACE.

a) 1:n

b)m:m

c)n:1

d) none

Comments

it depends on situation if it is asking about 1NF and there is total participation then it will be combine otherwise no.

Answer 1

IF A RELATION HAS m:n CARDINALITY than we are not abke to combine the table .

(B) option ans.

Comments

suppose employee table with(eid,ename,blah blah blah) with eid as primary key and department table with (dno,dname,blah blah blah) with dno as primary key, then we can surely combine eid and dnotogether combined as primary key and make a seperate table. so the no of tables are becoming 3. so does this mean since we cant do it in 2 tables so not minimized?(please recheck)

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yeah@vijaycs i think the same too, thats what the question is asking

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@resilient. yes, thats what asked.

Answer 2

I guess answer should be none. 

Because we can combine any CARDINALITY relations in worst case it will contain REDUNDANT data only. It is not advisible to store M*N reltion on 1 table but it doesnt mean we cant store in 1 table.

Hence, answer is D but here we have redundant data.

Kunal and Vijaycs feel free to correct me :)

Answer 3

For 1:m, m:1 and 1:1 we can perform merging for minimization of tables but it’s not possible for m:n relationship, instead we need to make one table in which we add primary keys of neighbouring entities. So, no minimization possible for m:n relationship. Hence, option B is correct answer.