Outer join from Parent to Child Tabular Model

[Merri]

Has anyone had any success in creating an outer join from a parent tabular model to a child TM?
I created a filter in the parent TM in the form:
where child.ItemID is null or child.ItemID = parent.ItemID

which should accomplish an outer join, but returns only the inner join part.
When I created a filter in the form:
where parent.ItemID not in (child.ItemID) or parent.ItemID in (child.ItemID)

I get the correct result set, but of course the performance is horrible because this is doing a cross join.
A further issue is that even though the latter filter returns the correct result set when running the TM, it returns nothing to the report itself.

Has anyone struck this problem? Any ideas how to solve this? I'm using 1.1 MR2.

[hksharma]

use tabular set with two tabular models with parent.itemid=child.itemid and parent.itemid not in child.itemid,union