Convert from UniqueIdentifier to BigInt and Back?

Question

declare @uu uniqueidentifier =  'C50B0567-F8CC-4219-A1E1-91C97BD9AE1B'
select @uu
declare @zaza bigint = ( select convert(bigint, convert (varbinary(8), @uu, 1)) )
select @zaza
select CONVERT( uniqueidentifier , convert( varbinary(16) , @zaza , 1 ) )

I thought I had a fast way to convert Unique Identifier values to a Big Int, and back. But there is a problem in my second convert. Can anyone comment on the right way to fully convert a GUID to a number and back? I am only getting part of the GUID and not the whole thing when I try to convert it back from the numeric representation to its original GUID.

I want to pass an integer (I think it would be classified as a "Large BigInt" in MSSQL?) to a remote system and just use characters 0-9, and still get the random uniqueness of NewId().

Solution

There is no problem with your second convert. When I run your SQL statement in SQL management studio, I get:

------------------------------------
C50B0567-F8CC-4219-A1E1-91C97BD9AE1B

(1 row(s) affected)


--------------------
7423352504965404994

(1 row(s) affected)


------------------------------------
C50B0567-F8CC-4219-0000-000000000000

(1 row(s) affected)

Since you are converting 8 byte value to 16-byte guid, half of guid will be zeroes, which is exactly what you are seeing.