COMPUTER SCIENCE AND ENGINEERING
DATABASE MANAGEMENT SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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ID
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registration no
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Department ID
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Street
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Detailed explanation-1: -6. Which one of the following cannot be taken as a primary key? Explanation: Street is the only attribute which can occur more than once.
Detailed explanation-2: -A primary key is a field in a table which uniquely identifies each row/record in a database table. Primary keys must contain unique values. A primary key column cannot have NULL values.
Detailed explanation-3: -Street addresses or driver license numbers are examples of primary keys used to uniquely identify (respectively) locations or cars. As another example, a database must hold all of the data stored by a commercial bank.
Detailed explanation-4: -We have different types of keys in the database. The primary key is a particular type of key that can uniquely identify the table rows. Primary keys must contain unique values and cannot be NULL . We can only have one primary key in a table.