SQL like querying on a DB with more than 1 key in a table

Question

We know that there is the concept of a primary key in traditional RDBMS systems. This primary key is basically used to index records in the table on this particular key for faster retrieval. I know that there are NOSQL stores like Cassandra which offer secondary key indexing but is there a way or an existing DB which follows exactly the same schema as in traditional RDBMS systems (i.e. a DB split into various tables to hold different kinds of data) but provides indexing on 2 or more keys.

An example of a use case for the same is:

There is a one-to-one mapping between 10 different people's names and their ages. Now if I keep this information in a table with the name of the person being the primary key, then retrieval of age given the name of a person is relatively faster than retrieving the name given the age of the person. If i could index both the columns, then the second case also would have been faster. An alternative to doing this with traditional RDBMS would be to have 2 tables with the same data with just the difference that the primary key in one of them is the name and in the other, it is the age but that would be a wastage of a large amount of space in case of large number of records.

Answer 1

It is sad to see no response on this question for a very long time. In all this time of doing some research on the same , I found FastBit Index as one of the plausible solutions for doing indexing on virtually every column of the record in a table. It also provides SQL like semantics for querying data and delivers performance of the order of a few milliseconds when queried on millions of rows of data (of the order of GBs).

Please suggest if there are any other NOSQL or SQL DBs which can deliver similar kind of functionality with a good performance level.