题解 | #统计各个部门的工资记录数#

SELECT
    s1.dept_no,
    s1.dept_name,
    COUNT(s2.salary) sum
FROM
    (
        SELECT
            d1.emp_no,
            d1.dept_no,
            d2.dept_name
        FROM
            dept_emp d1
            INNER JOIN departments d2 ON d2.dept_no=d1.dept_no
            
		) s1
		INNER JOIN salaries s2 ON s1.emp_no = s2.emp_no    
GROUP BY
	s1.dept_no 
ORDER BY
  s1.dept_no 
ASC