Issues updating a MySQL table using Python's MySQLdb.

Question

I am trying to UPDATE a MySQL table using Python's MySQLdb module. Although the query seems fairly simple it just won't update the information. Here is my code:

for username,info in users.iteritems():
  if info[0] > 0 and info[1] > 0:
    month = 8
    year = 2010
    cursor.execute("""
        UPDATE users_disk
        SET
            bytes = %s,
            quota_in_mb = %s
        WHERE
            username = %s AND
            month = %s AND
            year = %s
        """, (info[0], info[1], username, month, year))
    print "Username: %s; Rowcount: %d" % (username, cursor.rowcount)

The output looks like this:

Username: niu666; Rowcount: 0
Username: antuan; Rowcount: 0
Username: tuyo; Rowcount: 0
Username: angela; Rowcount: 0
Username: felipe; Rowcount: 0
Username: Meni; Rowcount: 0
Username: tronco; Rowcount: 0
Username: queque; Rowcount: 0
Username: cerel; Rowcount: 0

Which means none of the rows have been updated! The table has the following contents:

mysql> select * from users_disk;
+----+----------+-------+------+---------+-------------+
| id | username | month | year | bytes   | quota_in_mb |
+----+----------+-------+------+---------+-------------+
|  1 | niu666   |     8 | 2010 |   28672 |     1024000 | 
|  2 | antuan   |     8 | 2010 |   77824 |     4608000 | 
|  3 | tuyo     |     8 | 2010 |   28672 |     1024000 | 
|  4 | angela   |     8 | 2010 |   45056 |     2048000 | 
|  5 | felipe   |     8 | 2010 |   53248 |      307200 | 
|  6 | Meni     |     8 | 2010 |   86016 |     4096000 | 
|  7 | tronco   |     8 | 2010 | 3067904 |     1024000 | 
|  8 | queque   |     8 | 2010 |   61440 |     4608000 | 
|  9 | cerel    |     8 | 2010 |  110592 |     5632000 | 
+----+----------+-------+------+---------+-------------+
9 rows in set (0.00 sec)

And users is a dictionary with the following contents:

{'niu666': (28672, 1024000), 'tutk': (-1, -1), 'antuan': (77824, 4608000), 'tolin': (-1, -1), 'tuyo': (28672, 1024000), 'angela': (45056, 2048000), 'felipe': (53248, 307200), 'Meni': (86016, 4096000), 'tronco': (3067904, 1024000), 'queque': (61440, 4608000), 'cerel': (110592, 5632000), 'carok': (-1, -1), 'niu': (-1, -1)}

I think the issue might be related to username because if I remove it the update works. But of course I need to use it...

Any pointers/recommendations will be highly appreciated.

Thank you so much,

Unai Rodriguez

-------------------------- update -------------------------

Guys, I am using the following "ugly" workaround... that works:

for username,info in users.iteritems():
    if info[0] > 0 and info[1] > 0:
        # The user has positive values, its valid!
        cursor.execute("DELETE FROM " + dbtable + " WHERE username = %s AND month = %s AND year = %s", \
            (username, month, year))
        cursor.execute("INSERT INTO " + dbtable + " (id, username, month, year, bytes, quota_in_mb) VALUES (NULL, %s, %s, %s, %s, %s)", \
                                            (username, month, year, info[0], info[1]))

Still I am interested in knowing what is wrong with the UPDATE (first implementation). I will leave the script like that for now. Thank you so much.

Answer 1

Did you try COMMIT command after update as following?

cursor.execute("UPDATE animals SET species=%s WHERE name=%s",('TEST', 'Rollo'))

cursor.connection.commit();

Answer 2

Can you check if username in table and username from query have same length? If there is any padding (with space character) in table it may not show up in the SQL command prompt and will cause the update to match zero rows.

Also can you pass in the primary key of the table (id) along with the year and month rather than username?