Darren Neimke has an excellent article describing a couple of really interesting techniques for those of us working with Microsoft CRM's FetchXML query language.

He discusses using the IN operator as well as how to reverse-engineer a standard CRM QueryExpression to obtain the FetchXML code.

For those of you who are not developers and want to know what the heck I'm talking about: FetchXML is a method of generating an CRM database query using an series of pre-defined instructions written in XML.  You perform a query operation using the XML instructions and CRM will return to you a list of CRM records that match your criteria.

If you've ever used CRM's Advanced Find feature, then you've actually generated something similar to FetchXML during that process but never known it.