IDENTITY vs UNIQUEIDENTIFIER COLUMN

IDENTITY

Sl No	Advantage	Disadvantage
1	Identity column stores numeric values. Numeric value column have better performance in joins, indexes and conditions.	Range of values stored in identity column based on data type : bigint 2^63 (-9,223,372,036,854,775,808) to 2^63-1 (9,223,372,036,854,775,807) int -2^31 (-2,147,483,648) to 2^31-1 (2,147,483,647) smallint -2^15 (-32,768) to 2^15-1 (32,767) tinyint 0 to 255 If table size is large, it is quite possible it will run out of it and after some numeric value there will be no additional identity to use.
2	Numeric values are easier to understand for application users if they are displayed.

UNIQUEIDENTIFIER

Sl No	Advantage	Disadvantage
1	·        Unique across server	Uniqueidentifier column has string value i.e. {BAE7DF4-DDF-3RG-5TY3E3RF456AS10}. String values are not as optimal as integer values for performance when used in joins, indexes and conditions.
2	·        Since it is unique across server , allows easy merging of records from different databases	More storage space is required than INT
3	·        Allows easy distribution of databases across multiple servers
4	·        You can generate IDs anywhere, instead of having to roundtrip to the database
5	Most replication scenarios require GUID columns anyway