Retrieves all columns for a defined Data Extension in Salesforce Marketing Cloud

getColumns.xml

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soapenv:Header>
      <fueloauth xmlns="http://exacttarget.com">insertAccessTokenHere</fueloauth>
   </soapenv:Header>
  <soapenv:Body>
      <RetrieveRequestMsg xmlns="http://exacttarget.com/wsdl/partnerAPI">
        <RetrieveRequest>
            <ObjectType>DataExtensionField</ObjectType>
            <Properties>Name</Properties>
            <Filter xsi:type="SimpleFilterPart">
                <Property>DataExtension.CustomerKey</Property>
                <SimpleOperator>equals</SimpleOperator>
                <Value>insertDataExtensionExternalKeyHere</Value>
            </Filter>
        </RetrieveRequest>
      </RetrieveRequestMsg>
  </soapenv:Body>
</soapenv:Envelope>