PostgreSQL | EXAMPLES | AGGREGATE FUNCTIONS

Create a table employee with fields (EmpID, EName, Salary, Department, and Age).
Insert some records. Write SQL queries using aggregate functions and group by clause

A. Display the total number of employees.
B. Display the name and age of the oldest employee of each department.
C. Display the average age of employees of each department
D. Display departments and the average salaries
E. Display the lowest salary in employee table
F. Display the number of employees working in purchase department
G. Display the highest salary in sales department;
H. Display the difference between highest and lowest salary