Other monks have given you help towards a solution, but I noticed a misunderstanding that will not help you: you do not have two primary keys, you have one primary key that happens to be a 2-tuple of (lat, lon) values. While you will have to match it piecewise, it is conceptually a single datum.

In reply to Re: Update XML Values using two primary keys by jcb
in thread Update XML Values using two primary keys by pratikpooja

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