SELECT COUNT(first_name) AS Totalemployees ,SUM(salary) AS TotalSalary FROM employees;
SELECT department_id, COUNT(first_name) AS TotalEmployees, MAX(salary), MIN(salary) FROM employees GROUP BY department_id;
SELECT DISTINCT job_title,COUNT(first_name),COUNT(salary) FROM employees JOIN jobs ON employees.job_id=jobs.job_id GROUP BY job_title;
SELECT department_id,AVG(salary) FROM employees WHERE hire_date > '1998-07-10' GROUP BY department_id;
SELECT department_id,COUNT(first_name) FROM employees  GROUP BY department_id HAVING COUNT(first_name) > 2;
SELECT manager_id,COUNT(first_name) FROM employees GROUP BY manager_id HAVING COUNT(first_name) < 5;
SELECT department_id,AVG(salary) FROM employees WHERE hire_date > '1980-01-01' GROUP BY department_id HAVING AVG(salary) > 4000 && AVG(salary) < 10000;