Use DISTINCT and SUM in the same Query

Question

Good I have the following query:

SELECT
    SUM(a.valor - a.desconto - a.credito + a.frete)
FROM
    pedidos a,
    cadastro b
WHERE
    a.status = '2' 
    AND a.data >= '2019-03-29' 
    AND a.data <= '2019-04-29'
    AND a.id_cliente = b.id 
    AND b.id_cidade = '2378'

It returns me the value of 10.859,95. This value is correct. However I need to recover some more data and to do so assemble this query:

    SELECT
    SUM(a.valor + a.frete)
FROM
    pedidos a,
    cadastro b,
    produtos_pedidos c
WHERE
    a.status = '2' 
    AND a.data >= '2019-03-29' 
    AND a.data <= '2019-04-29'
    AND a.id_cliente = b.id 
    AND b.id_cidade = '2378'
    AND a.id = c.id_pedido
    AND c.grupo = '234'

The problem is that it returns me a much higher value, so I realized the error. The requests are being duplicated, because in a request I have several produtos_pedidos. How do I make the table SUM requests but without repeating the ID?

Answer 1

Tried to remove the table produtos_pedidos of join and using it in a filter with EXISTS?

SELECT
    SUM(a.valor + a.frete)
FROM
    pedidos a,
    cadastro b
WHERE
    a.status = '2' 
    AND a.data >= '2019-03-29' 
    AND a.data <= '2019-04-29'
    AND a.id_cliente = b.id 
    AND b.id_cidade = '2378'
    and EXISTS(
        SELECT 1
          FROM
              produtos_pedidos c
         WHERE
             c.id_pedido = a.id
             AND c.grupo = '234'
    )