Search Between Dates

Hello: I'm looking to create a search function that can take a starting and ending date from a user, and compare that with other start and end dates in a database. I would like it to check if any of the days within the users start and end dates fall within any days in the start and end dates within the database. I'm not sure if this can be accomplished on the SQL query, or if it needs to later check for this in an IF statement. Any help would be appreciated. Thanks, Kyle kyle@thedip.net