How to Give unique user id when many users registered at same time

thanx for ur advice marimuthu!!!

I'm generating random numbers as bruce told but i'm scared of  replication  still....

to create unique number in DB, u can use the below one.
CREATE TABLE Users
(
  ID          Int          NOT NULL IDENTITY CONSTRAINT PK_UserID PRIMARY KEY,
  UserName Varchar(50)  NULL
)

Thanx Bruce!!!
 
But i dont have any idea about using GUId..... is there any possibilities of replication if we generate integer random numbers...??

Syed,

Instead of assigning the next column ID, why not generate a random number?  Generate the number, then query your database to ensure that the number hasn't been used already.  If it hasn't, insert the new record (to reserve the new number) and update the record after the user enters the required details.  Do that instead of using an auto-incrementing column in the database.

Another way to do it would be to create another column that would be large enough to fit a GUID and use that instead.  Those are pretty much guaranteed to be unique because they're fairly long strings - but as a UserID (at-least internally) it would be pretty sure to prevent collisions.  Then just require the user to create a unique login based on their name or something.

-Bruce