如何打印左连接的结果

Question

I'm having issues showing the results of a left join in python. Here's the issue:

I have two tables. One Customers table and one Weights table that keep track of weights records for each customer.

Customers table:

pID   Name    
01    John
02    Charlotte

Weights table:

wID   pID    Weight
01    01     90
02    01     93
03    01     92
04    02     76
05    02     74

When i store my left join in a python cursor i get this result.

pID    Name    wID    Weight
01     John    01     90
01     John    02     93
01     John    03     92
02     John    04     76
02     John    05     74

My goal is to show:

pID: 01
Name: John
    wID: 01    Weight: 90
    wID: 02    Weight: 93
    wID: 03    Weight: 92

pID: 02
Name: Charlotte
    wID: 04    Weight: 76
    wID: 05    Weight: 74

Now the Python code. I have a Customer class that stores the person ID, Name and an array holding all of the weights registered for that person.

So this is my attemp to store all of the customers and their weights in a single list called customers.

    customers = []
    query = "SELECT * FROM customers LEFT JOIN weights ON customers.idcustomers = weigths.idcustomers"
    try:
        self.cur = self.connect()
        self.cur.execute(query)
        queryResults = self.cur.fetchall()
        self.desconectar()
    except Exception as e:
        print(e)
        pass
    for row in queryResults:
        found = False
        for cus in customers:
            if row[0] == cus.id:
                cus.weights.append(Weight(row[0],row[2],row[3]))
                found = True
        if found == False:
            newCustomer = Customer(row[0],row[1])
            newCustomer.weights.append(Weight(row[0],row[2],row[3]))
            customers.append(newCustomer)
    return customers

For some reason i get all of the weights added into each of the customers.

Results look like this:

pID: 01
Name: John
    wID: 01    Weight: 90
    wID: 02    Weight: 93
    wID: 03    Weight: 92
    wID: 04    Weight: 76
    wID: 05    Weight: 74

pID: 02
Name: Charlotte
    wID: 01    Weight: 90
    wID: 02    Weight: 93
    wID: 03    Weight: 92
    wID: 04    Weight: 76
    wID: 05    Weight: 74

I've been trying for a while to fix this and i don't really know why each person is storing every weight.

This code is a simplified version of the original script, i hope i didn't mess up!

Any help is welcome.. thanks in advance!

EDIT: The query results are right, i made a mistake translating the SQL line.

what's failing is the python code.

Answer 1

Make sure you join pID on both tables.

I'm not sure how you've defined the classes, but seems like the JOIN condition on your query it's joining pID with wID :

query = "SELECT * FROM customers LEFT JOIN weights ON customers.idcustomers = weighs.idweights"

So, check the result of your LEFT JOIN as it is to make sure the result it's as you expect.

Then, move onto the Python logic of appending the results. But I think that should be fine.

PS: Is there any difference between the classes Weight and Peso ?