Hello Sunil,
Join the two analytic view fields(each from separate projections P1 and P2) in a third projection P3. In P3, create a 'calculated column' Field C with the following expression,
IF(Isnull(FieldA),FieldB, FieldA)
You can find the details of the these expressions and functions in HANA SQL help.
Try this, read the help document and let us know if you run into errors or need more help.
Benedict