jeudi 21 janvier 2016

What to do next?

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.

This code is incomplete as I need to modify the program to store the role column in the Member table to complete the problem. And I cannot understand how to do it.

import json
import sqlite3

conn = sqlite3.connect('rosterdb.sqlite')
cur = conn.cursor()

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: ')
if ( len(fname) < 1 ) : fname = 'roster_data.json'

# [
#   [ "Charley", "si110", 1 ],
#   [ "Mea", "si110", 0 ],

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

for entry in json_data:

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

    print name, title

    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) VALUES ( ?, ? )''', 
        ( user_id, course_id ) )

    conn.commit()

Once the necessary changes are made to the program and it has been run successfully reading the given 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.

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