sql, i tried to do this but i couldn't get the result, can anyone help me how to do this : Starting with the date/time of July 20, 2001 10:40:12, display the following result table. Use the Dual table.

subtract 2 days
18-jul-01 10:40:12

add half a day
20-jul-01 22:40:12

add 4and half hours
20-jul-01 15:10:12
