重复行的SQL和值到第一个（或最后一个）

I want to merge the duplicated rows (with same doctype, docnum and item) and sum the value of their 'qtd' column to the first one or the last one. Then delete the duplicate rows keeping just the one that caries the total value. (The line number is not important after deleting it can allow not sequential numbers)I want to merge the duplicated rows (with same