While I was reviewing other programmer's work, I found out that most of the SELECT statements contain this keyword - "WITH (NOLOCK)". So, I posted this question to the programmer who is handling the job. His answer is quite simple, "we need this to reduce the query response time and then our program will run faster". And the actual fact is that, the programmer does not know the side effect of this keyword.
Yes, the query will run faster because it does not require to lock all the necessary records before reading it from the table. But, the side effects is that the data returned by the query might be "dirty" (i.e., the changes have not been committed).
If the program has read the data which have been rolled back by other user, it could lead to many unpredictable situation. This could lead to unsolvable mystery.
