Many_Students_in_Many_Courses

Author: runalb

Using Databases with Python/W4_Ass_1_Many_Students_in_Many_Courses.py

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+import json
+import sqlite3
+
+conn = sqlite3.connect('W4_Ass_1_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 = '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()
+
+sqlstr ='''
+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
+'''
+
+print()
+for row in cur.execute(sqlstr) :
+    print(str(row[0]))
+
+cur.close()