Hierarchical Query Oracle PLSQL

SQL>
SQL> CREATE TABLE employee (
  2    employee_id INTEGER,
  3    manager_id INTEGER,
  4    first_name VARCHAR2(10) NOT NULL,
  5    last_name VARCHAR2(10) NOT NULL,
  6    title VARCHAR2(20),
  7    salary NUMBER(6, 0)
  8  );
Table created.
SQL>
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 1         ,0            , 'James'  ,'Smith'  ,'CEO',800000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 2         , 1         ,'Ron'     ,'Johnson','Sales Manager',600000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 3         , 2         ,'Fred'    ,'Hobbs'  ,'Sales Person',200000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 4         , 1         ,'Susan'   ,'Jones'  ,'Support Manager',500000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 5         , 2         ,'Rob'     ,'Green'  ,'Sales Person', 40000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 6         , 4         ,'Jane'    ,'Brown'  ,'Support Person',45000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 7         , 4         ,'John'    ,'Grey'   ,'Support Manager',30000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 8         , 7         ,'Jean'    ,'Blue'   ,'Support Person',29000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 9         , 6         ,'Henry'   ,'Heyson' ,'Support Person',30000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 10        , 1         ,'Kevin'   ,'Black'  ,'Ops Manager',100000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 11        , 10        ,'Keith'   ,'Long'   ,'Ops Person',50000);
1 row created.
SQL>
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 12        , 10        ,'Frank'   ,'Howard' ,'Ops Person',45000);
1 row created.
SQL>
SQL> insert into employee (EMPLOYEE_ID, MANAGER_ID,FIRST_NAME,LAST_NAME,TITLE,SALARY)
  2                 values( 13        , 10        ,'Doreen'  ,'Penn'   ,'Ops Person',47000);
1 row created.
SQL>
SQL>
SQL>
SQL>
SQL> select * from employee;
EMPLOYEE_ID MANAGER_ID FIRST_NAME LAST_NAME  TITLE                    SALARY
----------- ---------- ---------- ---------- -------------------- ----------
          1          0 James      Smith      CEO                      800000
          2          1 Ron        Johnson    Sales Manager            600000
          3          2 Fred       Hobbs      Sales Person             200000
          4          1 Susan      Jones      Support Manager          500000
          5          2 Rob        Green      Sales Person              40000
          6          4 Jane       Brown      Support Person            45000
          7          4 John       Grey       Support Manager           30000
          8          7 Jean       Blue       Support Person            29000
          9          6 Henry      Heyson     Support Person            30000
         10          1 Kevin      Black      Ops Manager              100000
         11         10 Keith      Long       Ops Person                50000
         12         10 Frank      Howard     Ops Person                45000
         13         10 Doreen     Penn       Ops Person                47000
13 rows selected.
SQL>
SQL>
SQL> --Using the LEVEL Pseudo-Column:display the level in the tree
SQL>
SQL> SELECT LEVEL, employee_id, manager_id, first_name, last_name
  2  FROM employee
  3  START WITH employee_id = 1
  4  CONNECT BY PRIOR employee_id = manager_id
  5  ORDER BY LEVEL;
     LEVEL EMPLOYEE_ID MANAGER_ID FIRST_NAME LAST_NAME
---------- ----------- ---------- ---------- ----------
         1           1          0 James      Smith
         2          10          1 Kevin      Black
         2           2          1 Ron        Johnson
         2           4          1 Susan      Jones
         3          13         10 Doreen     Penn
         3           7          4 John       Grey
         3          11         10 Keith      Long
         3           5          2 Rob        Green
         3           3          2 Fred       Hobbs
         3          12         10 Frank      Howard
         3           6          4 Jane       Brown
         4           8          7 Jean       Blue
         4           9          6 Henry      Heyson
13 rows selected.
SQL>
SQL>
SQL>
SQL> drop table employee;
Table dropped.
SQL>
SQL>