For some reason this has come up and I’d been attending to it in XSL but I really needed it strait out of TCC. Here is the projection that will give that to you.
<quer:projection alias="FileExtension" xmlns:quer="http://www.taleo.com/ws/integration/query"> <quer:substring> <quer:field path="FileName"/> <quer:customFunction name="instr"> <quer:field path="FileName"/> <quer:string>.</quer:string> <quer:integer>-1</quer:integer> </quer:customFunction> <quer:integer>99</quer:integer> </quer:substring> </quer:projection>