psycopg2 query returns None

Question

I am new to python and programming in general. This bit of code will eventually be used in a larger application. I apologize ahead of time for any mistakes. I am trying to make a simple query from a table in a postgresql database. The only result comes back as None. Even though I know there is data there. Thank you in advance for any assistance.

import psycopg2

def connect():
    """Connects to the database so you can query the stats you require"""

    conn= psycopg2.connect("dbname='Nascar_Stats' user='postgres' \
                       host='localhost' password='xxxxxxxx'")
    print('Connected to DB')

    cur = conn.cursor()
    cur.execute("SELECT 'Track_Length' FROM t_tracks \
                     WHERE 'Track_ID' = 'Daytona';")

    length = cur.fetchone()
    print('Track Length = ', length)

    conn.close()

alecxe · Accepted Answer · 2017-12-11 05:01:21Z

1

The problem is the quotes around the Track_Length and Track_ID. Because of the quotes, column names are currently interpreted as actual strings leading to an unsatisfied comparison between strings Track_ID and Daytona. Which leads to 0 rows matching the query and length getting the None value.

Remove the single quotes around the column names:

cur.execute("""
    SELECT Track_Length 
    FROM t_tracks
    WHERE Track_ID = 'Daytona'
""")

answered Dec 11, 2017 at 5:01

alecxe

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1 Comment

Shadow Over a year ago

Or use double quotes around table names.

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