How to undo a SQL Server UPDATE query?

Question

In SQL Server Management Studio, I did the query below.
Unfortunately, I forgot to uncomment the WHERE clause.
1647 rows were updated instead of 4.

Answer 1

If you can catch this in time and you don't have the ability to ROLLBACK or use the transaction log, you can take a backup immediately and use a tool like Redgate's SQL Data Compare to generate a script to "restore" the affected data. This worked like a charm for me. :)