GUID (Globally Unique Identifier) in SQL Server
The GUID (uniqueidentifier) data type is one of the most interesting data types available. uniqueidentifier column holds a GUI, a string of 32 random hexa-decimal characters (0-9, A-F) in blocks separated by hyphens. A GUID will look like
5166AA1D-A18F-4D3C-A7CA-3F3CBF8CEE2B
EDCF4B8A-4154-449B-972A-2224F8450BF1
CEA4C383-51FD-4B99-A67D-F5C34D5F1013
5D9FDC84-632D-4450-B183-04CBBEE87DC6
GUIDs have both Pros and cons. GUIDs are pretty big in size and require 16 bytes of storage. This usually makes it slow during joins of large dataset.
Now you might think, What is so great about GUID? Although it occupies lot of space there are several advantages. First, a GUID will be a completely unique value and no other GUID in the world will share the same string. This means that you can use GUIDs as PKs on your tables if you will be moving data between databases. This technique prevents duplicate PKs when you actually copy data. GUIDs are widely used in Microsoft products to identify interfaces, replica sets, records, and other objects.
In Sql Server, you can create a new GUID by using the function NEWID(). This function is a non-deterministic function. It generates a new value every time you execute function .
Select NEWID()
the datatype is named in SQL as “uniqueidentifier”