SQL 2005 is a relational database model and multiple
users can access the data sitting in the server box. Let us think there is an
organization conducting a survey by taking help from their employees. Lat us
say that the cumulative outcome of their reply is updated in a single row. Now,
when two employees (The client application they use for the survey) try to
update the same row does sql server discard an update from one person?
Let us take one more example. There is big stock
exchange system and a client web application is retrieving a row as an enquiry
of knowing how a particular business stands in the stock market. But let us
again assume when a row is read; an update is half a way. Now the situation
leads some columns of the row has older values and some columns has the updated
values.
SQL
Server tackles the above situation by using the Transaction Isolation.