Relational-Algebra
August 27, 2024Computer-Networks
August 28, 2024Database-Management-System
| Question 759 |
If R is a relation in relational data Model and A1,A2,..An are the attributes of relation R, what is the cardinality of R expressed in terms of domain of attributes?
| |R|<=|dom(A1)X dom(A2)..dom(An)| | |
| |R|>=|dom(A1)X dom(A2)..dom(An)| | |
| |R|=max(|dom(A1)|,|dom(A2)|,..|dom(An)|) | |
| |R|=min(|dom(A1)|,|dom(A2)|,..|dom(An)|) |
Question 759 Explanation:
● In the context of databases, cardinality refers to the uniqueness of data values contained in a column.
● Cardinality refers to a number. It gives the number of unique values that appear in the table for a particular column.
● For eg: you have a table called Person with column Gender. Gender column can have values either ‘Male’ or ‘Female”.
● Then the cardinality of Gender column is 2, since there are only two unique values that could possibly appear in that column – Male and Female.
● Cardinality refers to a number. It gives the number of unique values that appear in the table for a particular column.
● For eg: you have a table called Person with column Gender. Gender column can have values either ‘Male’ or ‘Female”.
● Then the cardinality of Gender column is 2, since there are only two unique values that could possibly appear in that column – Male and Female.
Correct Answer: A
Question 759 Explanation:
● In the context of databases, cardinality refers to the uniqueness of data values contained in a column.
● Cardinality refers to a number. It gives the number of unique values that appear in the table for a particular column.
● For eg: you have a table called Person with column Gender. Gender column can have values either ‘Male’ or ‘Female”.
● Then the cardinality of Gender column is 2, since there are only two unique values that could possibly appear in that column – Male and Female.
● Cardinality refers to a number. It gives the number of unique values that appear in the table for a particular column.
● For eg: you have a table called Person with column Gender. Gender column can have values either ‘Male’ or ‘Female”.
● Then the cardinality of Gender column is 2, since there are only two unique values that could possibly appear in that column – Male and Female.