Update data on SQL with form submit

[AlesonITC]

Hi, I have got an SQL table with this columns for example:

ID

Month

Price1

Price2

Where pk is ID + Month.

Then I got 200 rows with data. When I tap or click in some row, and press "edit" button, it navigates to another screen with a form with the data of the row tapped or clicked loaded. The next step would be change "Price1" or "Price2" and submit the form to update the row. 

When I do it, it says that there are a registry with this pk because it tries to insert a new row with the data I wrote instead of modify the existent row.

Anyone knows how can I update the row instead of insert a new one with the editform?

Thx a lot. Regards.