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pythonmysql
Jesse485
Jesse485

Reputation: 13

Removing quotes from mysql query in Python

I know that this question has been asked in the past, but thorough searching hasn't seemed to fix my issue. I'm probably just missing something simple, as I'm new to the Python-mysql connector supplied by mysql.

I have a Python script which accesses a mysql database, but I'm having issues with removing quotes from my query. Here is my code:

import mysql.connector

try:
    db = mysql.connector.connect(user='root', password='somePassword', host='127.0.0.1', database='dbName')
    cursor = db.cursor()
    query = "select * from tags where %s = %s"
    a = 'tag_id'
    b = '0'
    cursor.execute(query, (a, b))
    print cursor
    data = cursor.fetchall()
    print data
except mysql.connector.Error as err:
    print "Exception tripped..."
    print "--------------------------------------"
    print err

cursor.close()
db.close()

My database is set up properly (as I'll prove shortly).

My output for this program is:

MySQLCursor: select * from tags where 'tag_id' = '0'
[]

Yet when I change my query to not use variables, for example:

cursor.execute("select * from tags where tag_id = 0")

Then my output becomes:

MySQLCursor: select * from tags where tag_id = 0
[(0, u'192.168.1.110')]

To me, this means that the only difference between my Cursor queries are the quotes.

How do I remove them from the query?

Thanks in advance.

Upvotes: 0

Views: 2838

Answers (2)

Sun Lemuria
Sun Lemuria

Reputation: 61

I encountered a similar problem using pymysql and have shown my working code here, hope this will help.

What I did is overwrite the escape method in class 'pymysql.connections.Connection', which obviously adds "'" arround your string.

better have shown my code:

from pymysql.connections import Connection, converters


class MyConnect(Connection):
    def escape(self, obj, mapping=None):
        """Escape whatever value you pass to it.

        Non-standard, for internal use; do not use this in your applications.
        """
        if isinstance(obj, str):
            return self.escape_string(obj)  # by default, it is :return "'" + self.escape_string(obj) + "'"
        if isinstance(obj, (bytes, bytearray)):
            ret = self._quote_bytes(obj)
            if self._binary_prefix:
                ret = "_binary" + ret
            return ret
        return converters.escape_item(obj, self.charset, mapping=mapping)


config = {'host':'', 'user':'', ...}
conn = MyConnect(**config)
cur = conn.cursor()

Upvotes: 0

user94559
user94559

Reputation: 60133

I personally believe this code is correct and safe, but you should be extremely skeptical of using code like this without carefully reviewing it yourself or (better yet) with the help of a security expert. I am not qualified to be such an expert.

Two important things I changed:

  1. I changed b = '0' to b = 0 so it ends up as a number rather than a quoted string. (This part was an easy fix.)
  2. I skipped the built-in parameterization for the column name and replaced it with my own slight modification to the escaping/quoting built in to mysql-connector. This is the scary part that should give you pause.

Full code below, but again, be careful with this if the column name is user input!

import mysql.connector

def escape_column_name(name):
    # This is meant to mostly do the same thing as the _process_params method
    # of mysql.connector.MySQLCursor, but instead of the final quoting step,
    # we escape any previously existing backticks and quote with backticks.
    converter = mysql.connector.conversion.MySQLConverter()
    return "`" + converter.escape(converter.to_mysql(name)).replace('`', '``') + "`"

try:
    db = mysql.connector.connect(user='root', password='somePassword', host='127.0.0.1', database='dbName')
    cursor = db.cursor()
    a = 'tag_id'
    b = 0
    cursor.execute(
        'select * from tags where {} = %s'.format(escape_column_name(a)),
        (b,)
    )
    print cursor
    data = cursor.fetchall()
    print data
except mysql.connector.Error as err:
    print "Exception tripped..."
    print "--------------------------------------"
    print err

cursor.close()
db.close()

Upvotes: 2

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