Does a T-SQL transaction get rolled back if cancelled?

Question

In haste, I stupidly ran a statement to update a table without qualifying it with a where statement. So it started to update all records in the table.

I immediately noticed the error and hit the 'Cancel Execution" button in SQL Server Management Studio, but it took a minute to stop running.

So my question is, did it roll back the changes or were they made until it was told to stop?

I can't tell which records were updated just by looking at them. I'd have to restore the table if it did make any changes.

Thanks.

I wanted to run:

Update tableA 
set newdate = '2019-01-01' 
where account = 'abc'

but instead I ran:

Update tableA 
set newdate = '2019-01-01'

The database is a transactional type database.

Answer 1

SQL Server has the default transaction behaviour by default. That means that each sentence you run in the query editor is like:

BEGIN TRANSACTION
<YOUR COMMAND>
COMMIT TRANSACTION

So, if you have cancelled before finished, the transaction should be rolled back.

Answer 2

If the query hasn't finished before being cancelled then yes, it was rolled back. Either whole update was executed or nothing was changed.