Do I need to call rollback if I never commit?

Question

I am connecting to a SQL Server using no autocommit. If everything is successful, I call commit. Otherwise, I just exit. Do I need to explicitly call rollback, or will it be rolled back automatically when we close the connection without committing?

In case it matters, I'm executing the SQL commands from within proc sql in SAS.

UPDATE: It looks like SAS may call commit automatically at the end of the proc sql block if rollback is not called. So in this case, rollback would be more than good practice; it would be necessary.

Final Update: We ended up switching to a new system, which seems to me to behave the opposite of our previous one. On ending the transaction without specifying committing or rolling back, it will roll back. So, the advice given below is definitely correct: always explicitly commit or rollback.

Answer 1

It should roll back on close of connection. Emphasis on should for a reason :-)

Proper transaction and error handling should have you always commit when the conditions for commit are met and rollback when they aren't. I think it is a great habit to always commit or rollback when done and not rely on disconnect/etc. All it takes is one mistake or incorrectly/not closed session to create a blocking chain nightmare for all :-)