Add values from a table field

Question

I have a table where I store the freight values, but when the cart is updated with the freight value, this value is also updated in the table. But if order #1111 has 3 products in the cart, it will include in this table the updated shipping values. See:

I would like to add the values of the Freight, but with the care of not adding 02 times the freight of the same order, which in case is 16.10. I tried that query, but it didn’t work:

SELECT SUM(ValorFrete) AS ValorTFrete FROM loja_carrinho WHERE StatusCompras = 'aguardando' GROUP BY ValorFrete

It returns me only a first value and does not sum the values.

When grouping by Request, returns this way:

Answer 1

First you must select the repeating items, and then add up the freight value, example:

SELECT SUM(ValorTFrete) FROM
(
    SELECT DISTINCT NumPedido, ValorTFrete           
    FROM loja_carrinho 
    WHERE StatusCompras = 'aguardando'
) AS t