Flask template with Left Join

index.html

{% set cur_msg_id = -1 %}
{% for row in rows %}
    {% if cur_msg_id != row['message_id'] %} 
        {% set cur_msg_id = row['message_id'] %}
        Message: {{ row['message_id'] }}<br/>
    {% endif %}
    {% if row['comment_id'] != None %}
        {{ row['first_name'] }} {{ row['last_name'] }}: {{ row['comment'] }}<br/>
    {% endif %}
{% endfor %}

server.py

from flask import Flask, render_template
# import the Connector function
from mysqlconnection import MySQLConnector
app = Flask(__name__)
# connect and store the connection in "mysql" note that you pass the database name to the function
mysql = MySQLConnector(app, 'mydb')
# an example of running a query
# print mysql.query_db("SELECT * FROM messages")

app.jinja_env.add_extension('jinja2.ext.loopcontrols')

@app.route('/')
def index():
    query = 'SELECT messages.id as message_id, message, comments.id as comment_id, comments.comment as comment, users.id as user_id, first_name, last_name, email FROM messages LEFT JOIN comments ON(messages.id = comments.message_id) LEFT JOIN users ON(comments.user_id = users.id)';

    rows = mysql.query_db(query);

    return render_template('index.html', rows=rows);
app.run(debug=True, host='0.0.0.0')