How to create query in inner query [sub query] ?

You gotta explain yourself

Can’t you keep chaining WixDataFilter methods? You can continue to refine the results by chaining, for example, multiple eq() calls together, checking that multiple columns match your criteria. I don’t think Wix Collections support the SQL concept of sub queries but I’m also not sure that’s particularly necessary. If you need a DB result to perform a further query, then do exactly that: wait for the result before creating the second one. Additionally you could process the initial results in Javascript.

Also what Carlos said. What are you actually trying to achieve?

i have 3 dataset’s in this one dataset i am creating reference fields .how to add form submission through inputs.