Consider a table with following structure: Employee(Emp_id, Emp_name, Dept, Desig, basic) In this table which attribute can be used as a primary key?
(a) Emp_id
(b) Emp_name
(c) Dept
(d) Desig
A primary key is an attribute which can uniquely identify the records in a relation/table.
Checking the options
(a) Emp_id - No two employees can have the same employee id, so it can be used as a primary key.
(b) Emp_name - 2 or more employees can have the same name, so it cannot be used as a primary key.
(c) Dept - There could be more than 1 employee in a department, so it cannot be used as a primary key.
(d) Desig - There could be more than 1 employee with the same designation, so it cannot be used as a primary key.
From the above explanation, it is clear that only Emp_id can be used as a primary key.
So, the correct answer is (A)
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