[PHP] What if 1,000 people access the database at one time?

[Phil Schwarzmann]

So let's say Bill is accessing a MySQL table and is about to UPDATE some
information on a particular row.  Meanwhile, Al is doing a sort on that
same table.
 
Couldn't Al's sorting possibly screw up Bill's updating??  Or does
MySQL have some built in functions that prevent this?
 
Thanks!
Phil