diadvantage & advantage of identy column

[farhad28]

dear sir/madam
please tell me about diadvantage & advantage of using identy column.

sincerely yours

[anaphaxeon]

an identity column allows for all of the records in your table to have a unique identifier. Without this you run the risk of having duplicate records, which means that you won't be able to run a delete statement, and go through a lot of hell to get the duplications out. The only tables that I don't use identifiers in are lookup tables that are used for many to many relationships. All tables should have primary keys, and all tables if not a lookup table should have a unique identifier.