How to select only 1 record per month with SQL

Question

I have a sales chart and would like to select customers' sales, but if the customer made more than one sale per month, I would like you to bring the oldest just, how could I do that?

I don’t have an SQL code to provide because I don’t know where to start, but I have the table in question:

How I wish it was the return:

Notice that line 2 is gone, because the customer "João" made 2 purchases in January and brought only the oldest purchase of it.

I’m just studying, these tables are just fictitious.

Answer 1

The way I understand it if you want the minimum value of the date per month (which is the oldest purchase) of a given name, example:

SELECT t1.id, 
    t1.nome,
    t1.data_compra, 
    t1.valor_compra 
FROM Compras t1
INNER JOIN (SELECT nome, MONTH(data_compra) as m, 
            MIN(data_compra) as c FROM Compras t2   
            GROUP BY nome, MONTH(data_compra)) AS t2 
  ON t1.nome = t2.nome AND t1.data_compra = t2.c

See online example

I made based on the two tables and with a INNER JOIN brought the most recent values by name, month and date.