Using Databases with Python - Many students in many courses (produce database from json file)

This application will read roster data in JSON format, parse the file, and then produce an SQLite database that contains a User, Course, and Member table and populate the tables from the data file.

Download this file and save it as roster_data.json. Move the downloaded file into the same folder as your roster.py program.

Once you have made the necessary changes to the program and it has been run successfully reading the above JSON data, run the following SQL command:

SELECT hex(User.name || Course.title || Member.role ) AS X FROM 
    User JOIN Member JOIN Course 
    ON User.id = Member.user_id AND Member.course_id = Course.id
    ORDER BY X

Find the first row in the resulting record set and enter the long string that looks like 53656C696E613333.

import json
import sqlite3
#connects to database, creates a sqlite file
conn = sqlite3.connect('rosterdb.sqlite')
cur = conn.cursor()

# Do some setup
cur.executescript('''
DROP TABLE IF EXISTS User;
DROP TABLE IF EXISTS Member;
DROP TABLE IF EXISTS Course;

CREATE TABLE User (
    id     INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
    name   TEXT UNIQUE
);

CREATE TABLE Course (
    id     INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT UNIQUE,
    title  TEXT UNIQUE
);

CREATE TABLE Member (
    user_id     INTEGER,
    course_id   INTEGER,
    role        INTEGER,
    PRIMARY KEY (user_id, course_id)
)
''')

fname = raw_input('Enter file name: ') #fname = 'roster_data.json'
if ( len(fname) < 1 ) : fname = 'roster_data.json'


str_data = open(fname).read()
json_data = json.loads(str_data)

for entry in json_data:

    name = entry[0];
    title = entry[1];
    role = entry[2];

    print name, title, role

    cur.execute('''INSERT OR IGNORE INTO User (name)
        VALUES ( ? )''', ( name, ) )
    cur.execute('SELECT id FROM User WHERE name = ? ', (name, ))
    user_id = cur.fetchone()[0]

    cur.execute('''INSERT OR IGNORE INTO Course (title)
        VALUES ( ? )''', ( title, ) )
    cur.execute('SELECT id FROM Course WHERE title = ? ', (title, ))
    course_id = cur.fetchone()[0]

    cur.execute('''INSERT OR REPLACE INTO Member
        (user_id, course_id, role) VALUES ( ?, ?, ?)''',
        ( user_id, course_id, role ) )

    conn.commit()

cur.execute('''
SELECT hex(User.name || Course.title || Member.role ) AS X FROM
    User JOIN Member JOIN Course
    ON User.id = Member.user_id AND Member.course_id = Course.id
    ORDER BY X''')