As has already ben stated, the autoincrement key is the best approach. If you are forced to increment it yourself:

select max(CustomerNumber + 1) from CustomerList
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Here is an easy way to get the newly created/incremented key using DBI, if you are working with an autoincremented field. Ater your insert, do this:

my $customer_number = $dbh->{'mysql_insertid'};
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