I have to say I avoid JOINs in Autodesk Infrastructure Map Server since it is always hit or miss (mostly miss) with getting them to work.
For example: I have a SQL Sever database with two simple tables one with INT/GEOM and the other with INT/NVARCHAR - 2 columns in each table and want to join on the two INT columns.
Do the two simple INT columns join? no.
So, I end up creating views in SQL Server and then struggle with the Schema Overrides (which expire when I add new tables etc to the database because I have to re-create the Schema Overrides each time the structure changes)
Or finally, since Joins don't work out the box, and VIEWS are a stuggle, I end up completely duplicating my data using Safe's FME Desktop to join my two data sources together.
All because the JOINs don't work very well, if at all, in Autodesk Infrastructure Map Server (versions 2006,2007,2008,2009,2010,2011,2012,2013 and 2014).