子查询 Oracle

Show all employees who were hired on the day of the week on which the highest number of employees were hired.
---查询在星期几入职的员工最多并显示出有哪些员工？
---解释：判断条件在员工表中先找出在”哪一天“，哪一天的判断条件是在员工表中找出”入职人数最多“的那一天
SELECT last_name, TO_CHAR(hire_date, 'DAY') day
  FROM employees
WHERE TO_CHAR(hire_date, 'DAY') =
       (SELECT TO_CHAR(hire_date, 'DAY')
          FROM employees
         GROUP BY TO_CHAR(hire_date, 'DAY')
        HAVING COUNT(*) = (SELECT MAX(COUNT(*))
                            FROM employees
                           GROUP BY TO_CHAR(hire_date, 'DAY')));