How to subtract hours from a date in Oracle so it affects the day also

Question

I\'m trying to subtract date from Oracle so it even effect the day as well. For example, if the timestamp is 01/June/2015 00 hours and if I subtract 2 hours, I want to be able

Answer 1

Others have commented on the (incorrect) use of 2/11 to specify the desired interval.

I personally however prefer writing things like that using ANSI interval literals which makes reading the query much easier:

sysdate - interval '2' hour

It also has the advantage of being portable, many DBMS support this. Plus I don't have to fire up a calculator to find out how many hours the expression means - I'm pretty bad with mental arithmetics ;)