# NCERT Solutions Class 12 Computer Science Database Concepts

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Chapter - Database Concepts

Question 1: What is relation? Define the relational data model.

Answer: A relation is a table having atomic values, unique row and unordered rows and columns. The relational mode represent data and relationship among data by a collection of tables known as relation, each of which has a number of columns with unique names.

Question 2: What are all the domain names possible in gender ?

Question 3: Give a suitable example of a table with sample data and illustrate Primary and Candidate Keys in it.

Answer: A table may have more than one such attribute/ group of attribute that identifies a row/tuple uniquely, all such attribute(s) are known as Candidate Keys. Out of the Candidate keys, one is selected as Primary Key,

Question 4: Differentiate between cardinality and degree of a table with the help of an example.

Answer: Cardinality is defined as the number of rows in table. Degree is the number of columns in a table, eg: Consider the following tables

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