How can I ignore the transactions that it was loaded previously?

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Hi,

In my data load, is there a way to ignore a transaction that it already was loaded previously in the last data load?

i'm asking this because:

1 - If I load the transactions without "Key" field, my transactions will be duplicated and
2 - If I load the transactions with "Key" field, the data load will be fail when it face with a transaction loaded previously and it will not load all the transactions including new transactions of my file.

Thanks

Regards,

Tales