Is possible to use a sub-table from a sub-table?? Is this a good practice?
Yes you can add nested sub tables as long as it makes sense.
So just make sure that each sub table is a good collection of items belonging logically to the same parent.
Good examples are:
Users
Addresses
Orders
Lines
Cars
Images
Owners
Contacts
The problem I found us that in que query builder you only see the first subtable. You cant see the nested subtable in subtable.
In your example you cant see Contacts table.
Yes this is per design. You see for each query the first sub tables level.
Adding this sub table to the results will enable you to do a double click on it and open a nested query.
So this way your are doing a nested query per sub table level.
So your sub table data is being returned nicely nested just as the sub tables.