You probably wouldn’t store any of "tel:", "fax:", and "urn:msisdn:" in a database, because the column name “msisdn” is enough. Those would make sense only for

You probably wouldn’t store any of "tel:", "fax:", and "urn:msisdn:" in a database, because the column name “msisdn” is enough. Those would make sense only for data exchange, primarily links on websites.