Does the row (table of database) lock hold during the transaction?

In a tranction,a update event happened, and it will lock the associated row of the table.after the update's completeness,and before the tranction rollbacks or commits,whether or not the row lock will hold?

I see from a book that in the following condition ,a dead lock will happen.

transaction 1:

UPDATE sales.parts SET onhand=onhand-10 WHERE id=1;        //lock 1
UPDATE sales.parts SET onhand=onhand-10 WHERE id=2;         //lock 2

transaction 2:
UPDATE sales.parts SET onhand=onhand-10 WHERE id=2; //lock 2
UPDATE sales.parts SET onhand=onhand-10 WHERE id=1; //lock 1
////waiting for transation 2 to release lock 1

And I infer from this ,the lock will hold until the transaction commits or rollbacks ,is it right? Received on Tue Jul 09 2002 - 03:36:31 CEST