GUID

DECLARE @Guid1 UNIQUEIDENTIFIER = '00000000-0000-0000-0000-000000000000';
PRINT @Guid1;
DECLARE @Guid2 UNIQUEIDENTIFIER = CAST(CAST(0 AS BINARY) AS UNIQUEIDENTIFIER);
PRINT @Guid2;
DECLARE @Guid3 UNIQUEIDENTIFIER = CAST(0x0 AS UNIQUEIDENTIFIER);
--0x0 is a literal of datatype varbinary(1) and value 0x00. (A single byte with all bits set to 0).
PRINT @Guid3;

DECLARE @Guid1 UNIQUEIDENTIFIER = NEWID();
PRINT @Guid1;