My ifnull is not working and commit and rollback

Hello guys,

I have a problem with using IFNULL, it isn't working.
 I solved the assignments , and when I run the script in the columns where I have null values nothing appears. It just prints evething except the columns with null values and theirs new values.

Also, I had a problem with Commit and Rollback. When I run this script:

select * from departments order by dept_no;
commit;
delete from departments where dept_no = 'd010';
select * from departments order by dept_no;
rollback ;
select * from departments order by dept_no;

In the end I should expect nothing to be changed right? And to be as at the beginning with d010?

But that doesn't happen and the value is still deleted.