my_app-1.1.xml

<?xml version="1.1" encoding="UTF-8" standalone="no"?>
<databaseChangeLog 
    xmlns="http://www.liquibase.org/xml/ns/dbchangelog" 
    xmlns:ext="http://www.liquibase.org/xml/ns/dbchangelog-ext" 
    xmlns:pro="http://www.liquibase.org/xml/ns/pro" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog-ext 
                        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-ext.xsd 
                        http://www.liquibase.org/xml/ns/pro 
                        http://www.liquibase.org/xml/ns/pro/liquibase-pro-4.1.xsd 
                        http://www.liquibase.org/xml/ns/dbchangelog 
                        http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-4.1.xsd">
    <changeSet author="Darin Pope" id="addColumn-countries-1">
      <addColumn tableName="countries">
        <column name="abc_xyz" type="VARCHAR(3)">
          <constraints nullable="false"/>
        </column>
      </addColumn>
    </changeSet>
</databaseChangeLog>