=head1 NAME
MySQL::Util::Lite::ColumnConstraint
=cut
=head1 ATTRIBUTES
=head2 REQUIRED
none
=cut
=head2 OPTIONAL
=head3 column_name
=cut
=head3 parent_column_name
=cut
=head3 parent_schema_name
=cut
=head3 parent_table_name
=cut
=head3 schema_name
=cut
=head3 table_name
=cut
=head1 METHODS