Question 114012 in PostgreSQL Question posted in
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Postgresql – psycopg2 – sum of prices

I seem to have relatively easy question, but I have a little problem. I would like to iterr through the column prices in table products and then sum the prices.
I know an easy solution would be to change sql query -> sum(price), but in my exercise I need to avoid this solution.

import psycopg2

connection = psycopg2.connect(
    host='host',
    user='user', 
    password='password',  
    dbname='dbname', 
)

cursor = connection.cursor()
sql = "select price from products"
cursor.execute(sql)

for price in cursor:
    print(sum(price))
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    figured it out:

    sum = 0
for price in cursor:
    sum = sum + price[0]
print(sum)

  2. 0

    You can iterate over the cursor directly:

        column_sum = sum(row[0] for row in cursor)

    Or you can use one of the various "fetch" methods to access the results and save them to a variable first.

    Your cursor has 3 methods for fetching:

    1. fetchone() returns a single row
    2. fetchmany(n) returns a list of n many rows
    3. fetchall() returns a list of all rows
        results = cursor.fetchall()
    column_sum = sum(row[0] for row in results)

    Note that in all cases one row of data is a tuple. This is the case even if you’re only selecting one column (a 1-tuple).

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