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Author: xchen012

W4_manytomany.py

@@ -0,0 +1,70 @@
+# 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 is Many-to-Many relationship between User and Course, a junction table of Member was 
+#   created to form a pair of one-to-many relationships. 
+# The date used was in roster_data.json file. The results was stored in rosterdb.sqlite file.
+
+import json
+import sqlite3
+
+conn = sqlite3.connect('rosterdb.sqlite')
+cur = conn.cursor()
+
+# executescript(): execute multiply SQL statement with one call
+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];
+    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()