em 
that we would like it to enforce a few rules on us. These rules
help us from making mistakes and introducing incorrect data into 
out tables. When we create our tables:
</font><pre><font size="4" color="blue">
cur.execute("'CREATE TABLE IF NOT EXISTS People 
    (id INTEGER PRIMARY KEY, name TEXT UNIQUE, retrieved INTEGER)"')
cur.execute("'CREATE TABLE IF NOT EXISTS Follows 
    (from_id INTEGER, to_id INTEGER, UNIQUE(from_id, to_id))"')
</font></pre><font color="black">We indicate that the <tt>name</tt