simple_queries.sql

-- Number of employees retiring
SELECT COUNT(first_name)
FROM employees
WHERE (birth_date BETWEEN '1952-01-01' AND '1955-12-31')
AND (hire_date BETWEEN '1985-01-01' AND '1988-12-31');

-- Join departments and dept_manager tables
SELECT d.dept_name,
	dm.emp_no,
	dm.from_date,
	dm.to_date
FROM departments AS d
INNER JOIN dept_manager AS dm
ON d.dept_no = dm.dept_no
WHERE dm.to_date = ('9999-01-01');

-- Employee count by department number
SELECT COUNT(ce.emp_no), de.dept_no
FROM current_employees AS ce
LEFT JOIN dept_emp AS de
ON ce.emp_no = de.emp_no
GROUP BY de.dept_no
ORDER BY de.dept_no;

-- Sales employees
SELECT ce.emp_no,
	ce.first_name,
	ce.lASt_name,
	d.dept_name
FROM current_employees AS ce
	INNER JOIN dept_emp AS de
		ON (ce.emp_no = de.emp_no)
	INNER JOIN departments AS d
		ON (de.dept_no = d.dept_no)
WHERE d.dept_name = 'Sales';