   0  WITH temp as (   0  SELECT 'A' as master , 0 Col from dual   0  UNION SELECT 'A' , 0  from dual   0  UNION SELECT 'B' , 0 from dual   0  UNION SELECT 'B' , 0 from dual   0  UNION SELECT 'C' , 0 from dual   0  UNION SELECT NULL , 0 from dual   0  UNION SELECT NULL , 0 from dual)   0  SELECT 