Indexing question

In SQL, given a table T, with two fields f1, f2,

is it possible to create an index such that the same record is indexed in the index, once with field f1 and once with field f2. (I am not looking for a compound index in which the key would look like <f1, f2>, instead there should be two entries in the index <f1> and <f2>).

we have a few use cases for the above, perhaps we need to alter the schema somehow to accommodate the above,

any advice is greatly appreciated ..

thanks