select distinct 
	l1.Num as ConsecutiveNums
from 
	Demo_table l1,
	Demo_table l2,
	Demo_table l3
where 
	l1.Id = l2.Id - 1
	And l2.Id = l3.Id -1
	And l1.Num = l2.Num
	And l2.Num = l3,Num
	;