This isn't so much a Perl question, I'd say.

Anyway, if you know the date ranges are exactly the same on all tables, but don't know the ranges, you only need to run two queries:

1) select all dates from table 1.
2) and as you loop through all the dates, select rows from all tables where date = the date in the row you're on in query 1.

In other words, normalize the tables!

-imran