SQL View - Union Between Two Feature Classes

Hi all,
Forgive me here, I've been looking online, but I can't seem to find the answer...

I'm trying to create a view, with the Union operator within my SDE Database to effectively combine multiple feature classes together.

The tables have the same schema but I'm getting the below error message:

Microsoft SQL Server Native Client 10.0: The geometry data type cannot be selected as DISTINCT because it is not comparable.

This is the syntax I'm using for the view...

SELECT * FROM GDA94_LL_NT_GNAF_GNAF_point
UNION
SELECT * FROM GDA94_LL_SA_GNAF_GNAF_point

I've gone through and tried selecting the Shape field out individually and I'm not having much joy at this stage.

I am organising SQL Training for myself, but until then, I've just hit a small brick wall.

Any help would be greatly appreciated!

Cheers,

Cory