I WANT TO RETRIEVE MAX VALUE FROM TWO COLUMN - SQL TABLE : WANT TO GET MAX VALUE FROM COLUMN COL1 AND COL2

Emp_id	col1	                    col1
1251	2019-01-25 00:01:35.000	   2019-01-25 08:56:30.000
1251	2019-01-25 15:15:06.000	   2019-01-25 16:09:25.000
1251	2019-01-25 18:00:26.000	    NULL