Consider you have a website visited by millions of people. 50 people or so fill in a registeration form and both press submit at exactly the same moment. Can SQL deal with all these requests at the same time, is there any chance it will accidentally generate the same primary key more than once or completely break?
How can it deal with so many continuous requests, if it will mess up the records in the table or insert incorrectly then is there something which can be done to overcome it?