Data comparison

Hi,

Good day to you.


1)I  have data feed in excel which I am converting to xml.And then I validate the xml data and insert data into sql server 2000.

2)Say If i am getting data for january  , My data feed will have data for january only.

But for February I will be getting the data both for jauray and february.For march I will be getting from january till march.SO this happenens for every month.SO the data feed will keep growing.

Questions for expert
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1)Since I am validating the data  in xml (as mentioned in step 1 above) Whats the best way I can Ignore the previous months record.Please note I am having data with 27000 records.

2)Then i have to update database ,SO whats the best way to ignore data not changed.

NOte this application is written in c#.net and sql server 2000.

Thanks for your help.

Narendra