Past Year - 2 Mark Questions

Computer Science - Class 12
Chapter 8 - Database Concepts

## (i) In the above table, can we have Qty as primary key.

Primary key refers to a set of one or more attributes which can uniquely identify tuples in a relation.

In the above table, there is a duplication of values in the column Qty. So the attribute Qty cannot uniquely identify the tuples in a relation. Hence, we cannot set Qty as the primary key.

## (ii) What is the cardinality and degree of the above table?

• Cardinality refers to the number of tuples/rows in a table.
• Degree refers to the number of attributes/columns in a table.

So for the above table,

Cardinality = 5

Degree = 4

### Transcript

Observe the following table and answer the parts (i) and (ii): (i) In the above table, can we have Qty as primary key. Answer: Primary key refers to a set of one or more attributes which can uniquely identify tuples in a relation. In the above table, there is a duplication of values in the column Qty. So the attribute Qty cannot uniquely identify the tuples in a relation. Hence, we cannot set Qty as the primary key. (ii) What is the cardinality and degree of the above table? Answer: Cardinality refers to the number of tuples/rows in a table. Degree refers to the number of attributes/columns in a table. So for the above table, Cardinality = 5 Degree = 4