Usually this sort of thing is done in SQL:

select min(contact_date)
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However, if you have your heart set on comparing the dates in Perl, you can get the dates out of the database in whatever format you like (this formatstring is for oracle and may require tweaking for sqlserver):

select to_char( contact_date, 'YYYYMMDD' )
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If you get dates in this format, you don't need to use ParseDate or Date_Cmp - earlier dates will be numerically less than later dates.