<?xml version="1.0"?>
<schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Setup/Declaration/Schema/etc/schema.xsd">
    <!-- Add custom field to invoice table -->
    <table name="sales_invoice" resource="sales" engine="innodb" comment="Sales Flat Invoice">
        <column xsi:type="varchar" name="xml_filename" length="255" comment="XML filename" />
        <column xsi:type="varchar" name="hdr_filename" length="255" comment="HDR filename" />
    </table>

    <!-- Add custom field to creditmemo table -->
    <table name="sales_creditmemo" resource="sales" engine="innodb" comment="Sales Flat Invoice">
        <column xsi:type="varchar" name="xml_filename" length="255" comment="XML filename" />
        <column xsi:type="varchar" name="hdr_filename" length="255" comment="HDR filename" />
    </table>
</schema>