Explain the subqueries with comparison operators.
Comparison operators can be used (like <, >, =, !> etc). Sub queries used with comparison operators must return a single value rather than a list to avoid error. Hence the nature of the database must be knows before executing such sub queries.
Example: To display employees who have been referred by John whose id 276
SELECT employeeID FROM employee. employee_name WHERE referenceID = (SELECT referenceID FROM employee.firstname WHERE EmpID = 276)
Example: names of all employees whose salary is greater than the average salery
SELECT Employee_ID FROM Employee.Emp_name WHERE salary > (SELECT AVG (salary) FROM Employee.Emp_name)
