Hi Shanti,
I believe you have already checked this article where we said how you will be able to find the template that has been used for a project:
CA PPM Tuesday Tip: Which template was a project created or copied from?
However, here I guess your requirement is a bit different, and you want to know if a task is used in a Project Template, that is existing in your system, or not. If my understanding is correct, then this is something you can try:
You can check in the PRTASK table as that will give you the parent project (as PRPROJECTID), and then you can use the same in INV_PROJECTS table and check if the IS_TEMPLATE column is 1 or 0.
So basically, you have to join the PRTASK and INV_PROJECTS tables to get what you want.
Hope this helps. Let me know if there is anything I missed. Will try to answer that as well.
Thanks,
Abhisek Dhar