I have a gridview that has several collums.users select product and then see their selection in this gridview.in this gridview users can input their quantity of every product and then the id of that product and quantity and name of that user must to store in database.if a user select a 4 quantity for a book for example , and i have 10 book in my databese I want to the number of book in my database change to 6.how should I do this?
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