Regarding your question about SQL queriers: you might want to have a look at OQL:
For external databases, the following might be of interest:
A possible solution would be to use an extra entity for your "Index" and associate the first one with it. You can choose the index you need via a refference selector, you can create new ones, delete old ones and show only your indices in a datagrid.
The benefit is also that you reduce redundancy.