-- https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/MIN.html
SELECT manager_id, last_name, hire_date, salary,
       MIN(salary) OVER(PARTITION BY manager_id ORDER BY hire_date
         RANGE UNBOUNDED PRECEDING) AS p_cmin
  FROM employees
  ORDER BY manager_id, last_name, hire_date, salary;