SQL & PL/SQL

Hello gurus,

      SELECT first_name || ' ' ||  last_name,level,

      employee_id,manager_id ,

      LPAD(' ', 2*level-1)||SYS_CONNECT_BY_PATH(last_name, '/') "Path"

      FROM employees

         START WITH manager_id  is null

         CONNECT BY PRIOR employee_id = manager_id;

I want to find out total number of employees working under King  which includes its immediate descendants plus childeren under that descendants until leaf.

Similarly for Kochhar total number of employees working under Kochhar which includes its immediate descendants plus childeren under that descendants until leaf.

I am trying to do it by sys connect by path , how can i achieve this , please assist