题解 | #统计各个部门的工资记录数#

SELECT d.dept_no,d.dept_name,COUNT(*) sum
FROM 
                                   
    dept_emp de LEFT JOIN departments d ON de.dept_no=d.dept_no
    INNER JOIN salaries s ON de.emp_no=s.emp_no
                                   
GROUP BY d.dept_no
ORDER BY d.dept_no;