Jody,
Thanks for such a quick reply. I was indeed going for this functionality to prune the branches of the union. Graphical view is an option, but as there are too many branches, it would have been easier to write the CE script.
Input parameter is not a good option for my use case. The beauty of union with constant value in a graphical view is that the filtering can be done by the end user directly on the displayed data (Ex: Analysis office) and get the benefit of branch pruning in the union.
I hope future versions of HANA can provide this functionality in CE script.
Regards,
Ramana