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Chapter 11 Database Concepts Solutions

Question - 11 : -
A table ‘studentl’ has 4 columns and 10 rows and table ‘student 2’ has 5 columns and 5 rows.If we take cartesian product of these two tables,what is the degree and cardinally of the resultant table?

Answer - 11 : -

Degree-4 ×5=20[no.of columns]
Cardinally – 10×5 = 50 [no.of rows]

Question - 12 : -
Observe the following table and answer the parts (i) and (ii) :
ncert-solutions-for-class-12-computer-science-c-database-concepts-4-13
  1. In the above table, can we have Qty as primary key.[Answer as yes/no]. Justify your answer.
  2.  What is the cardinality and degree of the above table ?

Answer - 12 : -

  1. We cannot use Qty as primary key because there is dulication of values and primary key value cannot be duplicate.
  2. Degree = 4

Question - 13 : -
What do you understand by Union & Cartesian product in the relational algebra ?

Answer - 13 : -

Union of R and S : The Union of two relations is a relation that includes all the tuples that are either in R or in S or in both R and S. Duplicate tuples are eliminated.
Cartesian Product: The Cartesian Product is an operator which works on two sets. It combines the tuples of one relation with all the tuples of the other relation.
Example: Cartesian Product
 
The Union is an operator which works on two sets. It combines the tuples of one relation with all the tuples of the other relation such that there is no duplication.
 

Question - 14 : -
Explain the concept of union between two tables, with the help of appropriate example.

Answer - 14 : -

The union operation denoted by ‘U’ combines two or more relations. The resultant of union operation contain tuples that are in either of the table or in both tables.
For example :

Question - 15 : -
In the following 2 tables, find the union value of Student 1 and Student 2.

Answer - 15 : -

The resultant table is
 

Question - 16 : -
Observe the table ‘Club’ given below :
ncert-solutions-for-class-12-computer-science-c-database-concepts-4-17
  1. What is the cardinality and degree of the above given table ?
  2. If a new column contact_no has been added and three more members have joined the club then how these chages will affect the degree and cardinality of the above given table.

Answer - 16 : -

1. Cadinality: 4
Degree: 5
2. Cadinality: 7
Degree: 6

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