CONNECT BY PRIOR - Hierarchical queries

CREATE TABLE emp (eid NUMBER(3), ename VARCHAR2(20), mgr NUMBER(3));

        BEGIN
        INSERT INTO emp VALUES(100 , 'Murugappan', NULL);
        INSERT INTO emp VALUES(101 , 'Senthil'   , 100);
        INSERT INTO emp VALUES(102 , 'Karthic'   , 101);
        INSERT INTO emp VALUES(103 , 'John'      , 102);
        INSERT INTO emp VALUES(104 , 'Nagaraj'   , 100);
        INSERT INTO emp VALUES(105 , 'Selva'     , 104);
        END;
        /

Sample 1:

        SELECT eid, ename, mgr, PRIOR ename, LEVEl
        FROM emp
        CONNECT BY PRIOR eid = mgr
        START WITH mgr IS NULL;   
                
Sample Output

      
              
Sample 2:
       
        SELECT lpad(' ',5*level-1)||ename as ename
        FROM    emp
        START WITH mgr IS NULL
        CONNECT BY NOCYCLE PRIOR eid = mgr;

Sample output

    -----------------------
           ENAME        
    -----------------------
     Murugappan         
        Senthil               
             Karthic         
                  John        
        Nagaraj             
             Selva            
    -----------------------         
            
Sample 3: 

        SELECT eid, LPAD(' ', LEVEL*5, ' ')||ename NAME , mgr, PRIOR ename, LEVEL
        FROM emp
        CONNECT BY PRIOR eid = mgr
        START WITH mgr IS NULL;

Sample output

        
       
        DROP TABLE emp;