Question

My goal is to check if an e-mail already exists in the mysql database. I am pulling the information into the variable from a webform (string). I currently have the following code:

import MySQLdb

db = MySQLdb.connect("localhost","username","password","databasename")
cursor = db.cursor()
if cursor.execute("select count(*) from registrants where email = " + "'"emailvar"'") == 0:
    print "it doesn't exist"

When I attempt to access the page I get an internal server error. I narrowed down the error to the “‘”emailvar”‘”, and the code works fine, but e-mails have “@” and “.” which cause SQL syntax errors. I attempt to escape them utilizing “‘” “‘” opening and closing parenthesis, but it does not work and crashes the web page.

Answer 1

You want:

query = 'select count(*) from registrants where email=%s'
cursor.execute(query, emailvar)
if next(cursor, None) is None:
    # whatever

But would look at .fetchone() which should work, and also EXISTS in SQL (whereby it should have a unique constraint and let the DB work it out) and return a boolean-esque empty result.