#1

SELECT 
    COUNT(*)
FROM
    employees;

#2

SELECT 
    COUNT(*)
FROM
    employees
WHERE
    department_id = 6;

#3

SELECT 
    COUNT(*)
FROM
    employees
WHERE
    job_id = 9;

#4

SELECT
	department_id,
	COUNT(*)
FROM
	employees
GROUP BY
	department_id;

#5

SELECT
	e.department_id,
	department_name,
	COUNT(*)
FROM
	employees e
INNER JOIN departments d ON d.department_id = e.department_id
GROUP BY
	e.department_id;

#6

SELECT
	e.department_id,
	department_name,
	COUNT(*)
FROM
	employees e
INNER JOIN departments d ON d.department_id = e.department_id
GROUP BY
	e.department_id
ORDER BY
	COUNT(*) DESC;

#7

SELECT
	e.department_id,
	department_name,
	COUNT(*)
FROM
	employees e
INNER JOIN departments d ON d.department_id = e.department_id
GROUP BY
	e.department_id
HAVING
	COUNT(*) > 5
ORDER BY
	COUNT(*) DESC;

#8

SELECT 
    COUNT(job_id)
FROM
    employees;

#9

SELECT 
    COUNT(DISTINCT manager_id)
FROM
    employees;