We will need more information than you have provided,

Can you post the DDL Create for the table and sample data, along with expected results.

EDIT : Ideally you should not be using a GUID (Unique identifier) for an ID column, as in larger schemas it makes looking up single data rows simpler.

eg

Apart from storage considerations, Which of the following is easier to understand?

SELECT * FROM aTable Where Id='9B91D096-2F5F-4C86-AFFE-A68019ADD89A';

--Or

SELECT * FROM aTable Where Id=14556';

You might not have control over the database or the schema but just for reference.