Does SQL Server allow constraint violations (i.e. deferred constraints) in a transaction as long as the transaction has not been committed yet?

I have a running, uncommitted transaction and while this transaction is running, I will change my data so that it will violate some constraints (like having duplicate primary keys for example). When I commit the transaction, the data will be in consistent, valid state. Is this generally allowed in SQL and specifically in MS SQL Server?

sql sql-server transactions constraints
Edit
Report