Question

Q4) In star schema with three dimensions (state, time, client) PK of FACT table will be .

A) combination of Pks of state and time

B) combination of Pks of state, time and client

C) there is no PK in Fact table

D) None of the above

Answer 1

Correct Answer: B

Explanation:

A candidate key is an attribute or set of attributes that uniquely and minimally identify an entity instance in an entity set or record in a table. In a single table, there may be more than one candidate keys.

The primary key is one of the selected candidate keys to identify the record uniquely.  

The option 'A' is incorrect because the star schema has three dimensions, so the primary key can't be the combination of two dimension's primary keys.

The option 'B' is correct because the star schema has three dimensions, so the primary key will be the combination of all three dimension's primary keys.

The option 'C' is incorrect because the fact table should have a primary key and that primary key will be a composite key.

The option 'D' is incorrect because the option 'B' is correct.

So, only the option 'B' is correct.