Sorry, don't have ready access to my sql queries as I am in a cafe for the next several hours. But, the way we store the data are as "periods" which have starting age and ending age. Once again, the following may describe the dataset well -- 'a' lies completely within 'b'. However, 'b' started sometime during 'c' and ended sometime during 'd'. 'c', in turn, lies completely within 'e'... and so on.

I am looking for alternative ways to store such data, and then use Perl to query it so that given a "period", I can find the most nearest period that completely contains it.

If the above is not enough to convey the question clearly, I will submit more information, probably toward the end of the day, or tomorrow, with hopefully some of the sql queries.