Python MySQL data manipulation
<p>i have an assignment for uni, i've run into a wall, and i can't seem to get it working no amtter what i try.</p>

<p>So, this assignment is focused on accessing a MySQL database from Python, and viewing and arranging the data. The database is called inb104 and two tables exist, cars_for_sale and car_details.</p>

<p>Here is my code</p>

<pre><code>def top_N_expensive(num_of_highest):
connection = MySQLdb.connect(host='localhost', user='root', passwd='root',\
                                                                 db='inb104')
cursor = connection.cursor()
sql = "SELECT cars_for_sale.make, cars_for_sale.model, +'$'+car_details.price \
            FROM cars_for_sale, car_details WHERE cars_for_sale.CarId = car_details.CarId \
            ORDER BY price DESC,price LIMIT " + str(num_of_highest)
cursor.execute(sql) 
rows = cursor.fetchall()
for row in rows:
    print row[0], row[1], row[2]
cursor.close()
connection.close()
</code></pre>

<p>Now when i run this code the test cases fail, this is just one of the test cases but the rest are the same</p>

<pre><code>File "__main__", line 4, in __main__
Failed example:
top_N_expensive(10)
Expected:
VOLKSWAGEN GOLF $1300000
MERCEDES-BENZ SL $329990
BMW 3 $299990
MERCEDES-BENZ SL $249990
PORSCHE 911 $249990
MERCEDES-BENZ SL $224990
PORSCHE 911 $219990
PORSCHE 911 $190000
PORSCHE 911 $184990
BMW M5 $180000
Got:
VOLKSWAGEN GOLF 1300000.0
MERCEDES-BENZ SL 329990.0
BMW 3 299990.0
MERCEDES-BENZ SL 249990.0
PORSCHE 911 249990.0
MERCEDES-BENZ SL 224990.0
PORSCHE 911 219990.0
PORSCHE 911 190000.0
PORSCHE 911 184990.0
BMW M5 180000.0
</code></pre>

<p>As you can see, it's failing because there is a zero at the end and there is no $ at the beginning, anyone know the problem?</p>

<p>EDIT: After adding this new code</p>

<pre><code>for row in rows:
    print "%s %s $%d" % (row[0], row[1], row[2]) 
</code></pre>

<p>I got 3/4 test case passes, i don't know why the last one isnt passing, but here is the test case dump</p>

<pre><code>Trying:
top_N_expensive(10)
Expecting:
VOLKSWAGEN GOLF $1300000
MERCEDES-BENZ SL $329990
BMW 3 $299990
MERCEDES-BENZ SL $249990
PORSCHE 911 $249990
MERCEDES-BENZ SL $224990
PORSCHE 911 $219990
PORSCHE 911 $190000
PORSCHE 911 $184990
BMW M5 $180000

Warning (from warnings module):
File "Z:\Documents\top_N_expensive.py", line 82
cursor.execute(sql)
Warning: Truncated incorrect DOUBLE value: '$'
ok
Trying:
top_N_expensive(15)
Expecting:
VOLKSWAGEN GOLF $1300000
MERCEDES-BENZ SL $329990
BMW 3 $299990
MERCEDES-BENZ SL $249990
PORSCHE 911 $249990
MERCEDES-BENZ SL $224990
PORSCHE 911 $219990
PORSCHE 911 $190000
PORSCHE 911 $184990
BMW M5 $180000
MERCEDES-BENZ E55 $179990
MERCEDES-BENZ CLS $179990
PORSCHE 911 $165000
PORSCHE 911 $164900
PORSCHE 911 $161950
**********************************************************************
File "__main__", line 17, in __main__
Failed example:
top_N_expensive(15)
Expected:
VOLKSWAGEN GOLF $1300000
MERCEDES-BENZ SL $329990
BMW 3 $299990
MERCEDES-BENZ SL $249990
PORSCHE 911 $249990
MERCEDES-BENZ SL $224990
PORSCHE 911 $219990
PORSCHE 911 $190000
PORSCHE 911 $184990
BMW M5 $180000
MERCEDES-BENZ E55 $179990
MERCEDES-BENZ CLS $179990
PORSCHE 911 $165000
PORSCHE 911 $164900
PORSCHE 911 $161950
Got:
VOLKSWAGEN GOLF $1300000
MERCEDES-BENZ SL $329990
BMW 3 $299990
MERCEDES-BENZ SL $249990
PORSCHE 911 $249990
MERCEDES-BENZ SL $224990
PORSCHE 911 $219990
PORSCHE 911 $190000
PORSCHE 911 $184990
BMW M5 $180000
MERCEDES-BENZ CLS $179990
MERCEDES-BENZ E55 $179990
PORSCHE 911 $165000
PORSCHE 911 $164900
PORSCHE 911 $161950
Trying:
top_N_expensive(1)
Expecting:
VOLKSWAGEN GOLF $1300000
ok
Trying:
top_N_expensive(0)
Expecting nothing
ok
1 items had no tests:
__main__.top_N_expensive
**********************************************************************
1 items had failures:
1 of   4 in __main__
4 tests in 2 items.
3 passed and 1 failed.
***Test Failed*** 1 failures.
</code></pre>

<p>So, don't know why this is failing now, very strange.</p>

<p>Heres the updated Query</p>

<pre><code>def top_N_expensive(num_of_highest):
connection = MySQLdb.connect(host='localhost', user='root', passwd='root',\
                                                                 db='inb104')
cursor = connection.cursor()
sql = "SELECT cars_for_sale.make, cars_for_sale.model, +'$'+car_details.price \
            FROM cars_for_sale, car_details WHERE cars_for_sale.CarId = car_details.CarId \
            ORDER BY price DESC, make, model DESC" + str(num_of_highest)
cursor.execute(sql) 
rows = cursor.fetchall()
for row in rows:
    print "%s %s $%d" % (row[0], row[1], row[2]) 
cursor.close()
connection.close()
</code></pre>

<p>Test cases</p>

<pre><code>Trying:
top_N_expensive(10)
Expecting:
VOLKSWAGEN GOLF $1300000
MERCEDES-BENZ SL $329990
BMW 3 $299990
MERCEDES-BENZ SL $249990
PORSCHE 911 $249990
MERCEDES-BENZ SL $224990
PORSCHE 911 $219990
PORSCHE 911 $190000
PORSCHE 911 $184990
BMW M5 $180000
**********************************************************************
File "__main__", line 4, in __main__
Failed example:
top_N_expensive(10)
Exception raised:
Traceback (most recent call last):
  File "C:\Program Files\Python27\lib\doctest.py", line 1254, in __run
    compileflags, 1) in test.globs
  File "&lt;doctest __main__[0]&gt;", line 1, in &lt;module&gt;
    top_N_expensive(10)
  File "Z:\Documentstop_N_expensive.py", line 82, in top_N_expensive
    cursor.execute(sql)
  File "C:\Program Files\Python27\lib\site-packages\MySQLdb\cursors.py", line 174, in execute
    self.errorhandler(self, exc, value)
  File "C:\Program Files\Python27\lib\site-packages\MySQLdb\connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DESC10' at line 1")
</code></pre>
