What is the advantage of using XML with regards to SQL?

[Evellawen]

I've seen a few relational databases where the XML directly mirrors the SQL, and I was wondering if anyone could give me some insight as to why people use XML over other options. I was under the impression that it was more a personal preference, but I was told by a classmate that XML is considered "better" ie more efficient in certain cases. So I wanted to pose the question to you folks, because frankly I wanted a second opinion.The question: When would you use XML instead of ColdFusion or PHP (or other alternatives)? What are some inherent advantages that would make it a more desirable option? For example, this is what the XML might look like:\[code\]<data><dataObject name="Test"> <primaryKey>Num</primaryKey> <foreignKey dataObject="Test" key="Num"/> <datums> <datum type="integer" key="itemRecnum" label="Item Recnum" data="http://stackoverflow.com/questions/9282227/required"/> <datum type="string" key="status" label="Status" data="http://stackoverflow.com/questions/9282227/required"/> <datum type="integer" key="idnumber" label="ID Number" data="http://stackoverflow.com/questions/9282227/required"/> </datums> <constraints/></dataObject></data>\[/code\]So in the SQL server, each of these have a 1-1 correspondence, with each datum type being a column. Can someone please explain what the advantages of using XML to pull from the database are? What exactly is happening here and why is it used over CF or PHP? And how is it pushing and pulling from the database? What if you were to mix the two? Perhaps one would use coldfusion for inserts, and xml just for views?