Hi All,

Is uniqueidentifier is always unique ?

e.g I have a database named "mydatabse" ,where there are 7 table with uniqueidentifier are set to the Primary key Columns.They have default newid() that creates unique identifier for those primary key columns.

Now in one of my SP i have created temp table like

DECLARE @UserProfile table(NewKeyID uniqueidentifier,UserGUID varchar(36), UserName varchar(50))
insert into @UserProfile values(newid(),'A1','B1');
insert into @UserProfile values(newid(),'A2','B2');
insert into @UserProfile values(newid(),'A3','B3');
insert into @UserProfile values(newid(),'A4','B4');

select * from @UserProfile

Now "NewKeyID" which is unique identifier column will always have a unique value??(and it will not match with the other primary key column value)??

Any input or pointer would be a great help!!

Cheers :)

vinod

__________________
Cheers :)

vinod

As near as I can remember the GUID in SQL Server is based off of the MAC address of the NIC and the current system time so yes the GUID *should* always be unique. (I believe there is some mathmatical inprobablity whereby you can wind up with a duplicate guid but the chances are so low it isn't worth worrying about)

To this end I see nothing wrong with the structure you have shown in your post, in fact I am currently working in a system where we employ this very same technique and have not had an issue with it thus far.

hth.
-Doug

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They used to be created from MAC but no longer. They are supposed to unique in space and time but there's always the chance that two are created the same and the they are also both used in your application. According to quantum physics there's also the chance that a cold cup of water can start to boil without being externally heated, both events are about as equally unlikely.

--

Joe (Microsoft MVP - XML)

Thank you Doug and Joe..



Cheers :)

vinod

Hahaha, thanks for that. I am sure that will come in handy if I have to explain the same question to someone...

Imar


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Imar Spaanjaars
http://Imar.Spaanjaars.Com
Everyone is unique, except for me.
Author of Beginning ASP.NET 3.5 : in C# and VB, ASP.NET 2.0 Instant Results and Dreamweaver MX 2004
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