Question

In order to use newid() in a UDF, I’ve created a view that can help me:

create view RandomUUID as select newid() as UUID

In this way, UDFs can now get access to newid(). Cool.

My question, however, is what is the best way to select this? Does it make sense to add a TOP 1 or (nolock) to the query in my UDF? As in:

select UUID from RandomUUID

vs.

select top 1 UUID from RandomUUID (nolock) -- Or any other combo of query modifiers

UPDATE:

This SqlFiddle demonstrates how this is being used.

Answer 1

There is no reason to add (nolock) because there is no record involved to lock! For the record, (NOLOCK) should be written as WITH (nolock) from SQL Server 2008 onwards (or was it 2005).

TOP (1) will add a SORT operator here that will be extraneous, since there is only ever one row created.

---

You can create it like this:

create view RandomUUID as select newid() as UUID;
GO

create function give_me_a_new_id ()
returns uniqueidentifier as
begin
return (select UUID from RandomUUID);
end;
GO

Note: (nolock) will be optimized away, but TOP(1) adds a SORT operation as seen here (expand the Execution plans).