Fact to Fact Join in Cognos Framework Manager Or Stitch Query?

What is a Stitch Query?

A stitch query is the name given to the type of query that IBM Cognos BI produces when a user creates a query that contains two or more fact tables. A stitch query consists of independent sub-queries for each fact that are then joined together on common dimensions. This joining process is done using an outer join to ensure no data from any fact sub-query is lost during the stitch.

Please see the below links:

http://www.ibm.com/developerworks/data/library/cognos/reporting/advanced_report_design/page605.html
http://blogs.perficient.com/ibm/2012/05/17/cognos-concepts-stitch-query-in-cognos-reporting-explained/