I expect a pass thru query to be "pass thru", which imply that what ever that database underneath the query you pass will be supported as long as it complies with the database. With the query below, it took me a while to build it to pass all the exception that would allow it to almost be executed. But at the end I got below:
SELECT VALUE T FROM DATA_ENTRYs AS T WHERE T.RUN_NUMBER = @RUN_NUMBER AND T.THROUGH_DATE IS NULL AND T.DEVICE_ALIAS IN ( SELECT Q.NAME FROM DEVICESs AS Q WHERE Q.NAME = \"AABB - Bill\"
Exception:
The element type 'Edm.String' and the CollectionType 'Transient.collection[Transient.rowtype[(NAME,Edm.String(Nullable=True,DefaultValue=,MaxLength=Max,Unicode=True,FixedLength=False))](Nullable=True,DefaultValue=)]' are not compatible. The IN expression only supports entity, primitive, and reference types. , near IN set expression, line 1, column 117
So, this is kinda pass thru query. I think what I need is a documentation on the limitations and what are the supported operators, etc. that DevForce EF can understand.