First off, just to get it out of the way, Sybase does now support row level locking! (See Q6.1.11 for a description of the new features.) OK, that said and sone, if you think you need row level locking, you probably aren't thinking set based -- see Q6.1.1 for set processing.

The SQL Server uses locking in order to ensure that sanity of your queries. Without locking there is no way to ensure the integrity of your operation. Imagine a transaction that debited one account and credited another. If the transaction didn't lock out readers/writers then someone can potentially see erroneous data.

Essentially, the SQL Server attempts to use the least intrusive lock possible, page lock, to satisfy a request. If it reaches around 200 page locks, then it escalates the lock to a table lock and releases all page locks thus performing the task more efficiently.

There are three types of locks:

* page locks

* table locks

* demand locks