Best way to find updates in xml feed

I have an xml feed that I have to check periodically for updates. The xml consists of many elements and I'm looking to figure it out which is the best (and probably faster) way to find out which elements suffered updates from last time I've checked.

What I think of is to check first the lastBuildDate for modifications and if it differs from the previous one to start parse the xml again. This would involve keeping each element with all of its attributes in my database. But each elemen开发者_开发问答t can have different number of attributes as well as other nested elements. So if it would be to store each element in my database what would be the best way to keep them ?

That's why I'm asking for your help :) Thank you.

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Most modern databases will store your XML as a blob if you like. (You tagged PHP... MySQL? If so, use MEDIUMTEXT.) Store your XML and generate a diff when you get a new one. If you don't have an XML diff tool, canonicalize both XML listings then run a text diff.