We Keep Coding

Comparing SQL results with Python

I was looking for a way to my program to take 2 values from my database, compare them and update or insert some value.
I tried in sqlite3 but I didn't find a good solution and I tried on python, but when I run the program, the values are different and never match. I already look on google, here on stack overflow, but didn't find anything.
cursor.execute("select * from [Sistema]")
Teste = cursor.fetchall()
cursor.execute("select [SistemaOperacional] from [Sistema] where [SistemaOperacional] = 'teste'")
comparacao = cursor.fetchall()
testando = comparacao
for row in Teste:
#I was checking the values to see if they where equal
print(comparação[0]) #Value ('teste',)
print(row[0]) #Value 'teste'
if row[0] == comparação[0]:
cursor.execute("Update [Sistema] set [SistemaOperacional] = '1' where [VersaoBanco] = 3")
print('Executado')
break
else:
cursor.execute("insert into [Sistema] values ('9','9','1')")
print('não')
break
the output whas
('teste',)
teste
não
I wasn't finding a solution for this in sql, that's why I tried with python, but I'm open to listen any other suggestion than python

It's a pretty common problem for people unfamiliar with Python/MySQL to run into troubles receiving tuples back from querying. comparacao[0] is a tuple. Tuples are compared lexicographically by element, so you'd have to retrieve the first element (like #Gwyn Evans said) e.g. comparação[0][0] in order to compare it to your string row.
Here is a link to Python docs about comparisons: https://docs.python.org/2.0/ref/comparisons.html

I could be on the wrong track here, but isn't your comparação[0] itself a tuple, so you probably want to be comparing comparação[0][0] with row[0].

Python SQLite :IndexError: list index out of range

conn = database_connect()
if(conn is None):
return None
cur = conn.cursor()
try:
# Try executing the SQL and get from the database
sql = """SELECT *
FROM user
WHERE user_id**strong text** =%s AND password =%s"""
cur.execute(sql, (employee_id, password))
r = cur.fetchone()# Fetch the first row
rr = cur.fetchall()
cur.close() # Close the cursor
conn.close() # Close the connection to the db
except:
# If there were any errors, return a NULL row printing an error to the debug
print("Error Invalid Login")
cur.close() # Close the cursor
conn.close() # Close the connection to the db
return None
user_info = []
if rr is None:
print("worry")
return []
for n in rr:
user_info.append(n)
test = {
'info1': user_info[0],
'info2': user_info[1],
'info3': user_info[2],
'info4': user_info[3],
}
return test
Here is my code. First Implement the login function, and then get the user information, but there is a IndexError: list index out of range. How do I fix this?

Here:
r = cur.fetchone()# Fetch the first row
rr = cur.fetchall()
The call to fetchone() will consume the first row, so rr will contain n-1 rows.
Also, if your database allow duplicated user_id then you have a serious db design issue - whether user_id is (suppoed to be) the primary key or the "username" (loging name), it should really be unique. If it isn't, then you want to change your schema, and if it is indeed unique then obviously your query can only return (at most !) one single row, in which case rr is garanteed to always be empty (since you consumed the first row with the fetchone() call.
As a side note, here are some possible improvements:
this :
for n in rr:
user_info.append(n)
is completely useless - you are just building a shallow copy of rr, wo just work directly with rr instead.
Then do not assume you will always have four rows in your query result, so at least build your test dict dynamically:
test = {}
# enumerate(seq) yields an index, value tuple
# for each value in `seq`.
for num, row in enumerate(rr, 1):
key = "info{}.format(num)
test[key] = row
or more succintly:
test = {"info{}".format(num):row for num, row in enumerate(rr, 1)}
Note that this dict doesn't add much value compared to rr - you have "info" keys instead of numeric indexes and that's about all, so you could just directly use the rr list instead.
Last but not least, your try/except clause is too broad (too much code in the try block), the except clause will eat very valuable debugging information (the exact error message and the full traceback) and even worse, the error message you display assumes way too much about what really happens. Actually you probably shouldn't even have an except clause here (at least not until you really know what errors can happen here AND be properly handled at this point) so better to let the error propagate (so you get the full error message and traceback), and use the finally clause to close your connection instead:
sql = """SELECT *
FROM user
WHERE user_id**strong text** =%s AND password =%s"""
try:
cur.execute(sql, (employee_id, password))
r = cur.fetchone()# Fetch the first row
rr = cur.fetchall()
finally:
# this will always be executed whatever happens in the try block
cur.close() # Close the cursor
conn.close() # Close the connection to the db

Cannot validate query results

query = "SELECT serialno from registeredpcs where ipaddress = "
usercheck = query + "'%s'" %fromIP
#print("query"+"-"+usercheck)
print(usercheck)
rs = cursor.execute(usercheck)
print(rs)
row = rs
#print(row)
#rs = cursor.rowcount()
if int(row) == 1:
query = "SELECT report1 from registeredpcs where serialno = "
firstreport = query + "'%s'" %rs
result = cursor.execute(firstreport)
print(result)
elif int(row) == 0:
query_new = "SELECT * from registeredpcs"
cursor.execute(query_new)
newrow = cursor.rowcount()+1
print(new row)
What I am trying to do here is fetch the serialno values from the db when it matches a certain ipaddress. This query if working fine. As it should the query result set rs is 0. Now I am trying to use that value and do something else in the if else construct. Basically I am trying to check for unique values in the db based on the ipaddress value. But I am getting this error
error: uncaptured python exception, closing channel smtpd.SMTPChannel connected
192.168.1.2:3630 at 0x2e47c10 (**class 'TypeError':'int' object is not
callable** [C:\Python34\lib\asyncore.py|read|83]
[C:\Python34\lib\asyncore.py|handle_read_event|442]
[C:\Python34\lib\asynchat.py|handle_read|171]
[C:\Python34\lib\smtpd.py|found_terminator|342] [C:/Users/Dev-
P/PycharmProjects/CR Server Local/LRS|process_message|43])
I know I am making some very basic mistake. I think it's the part in bold thats causing the error. But just can't put my finger on to it. I tried using the rowcount() method didn't help.

rowcount is an attribute, not a method; you shouldn't call it.

"I know I am making some very basic mistake" : well, Daniel Roseman alreay adressed the cause of your main error, but there are a couple other mistakes in your code:
query = "SELECT serialno from registeredpcs where ipaddress = "
usercheck = query + "'%s'" % fromIP
rs = cursor.execute(usercheck)
This part is hard to read (you're using both string concatenation and string formatting for no good reason), brittle (try this with `fromIP = "'foo'"), and very very unsafe. You want to use paramerized queries instead, ie:
# nb check your exact db-api module for the correct placeholder,
# MySQLdb uses '%s' but some other use '?' instead
query = "SELECT serialno from registeredpcs where ipaddress=%s"
params = [fromIP,]
rs = cursor.execute(query, params)
"As it should the query result set rs is 0"
This is actually plain wrong. cursor.execute() returns the number of rows affected (selected, created, updated, deleted) by the query. The "resultset" is really the cursor itself. You can fetch results using cursor.fetchone(), cursor.fetall(), or more simply (and more efficiently if you want to work on the whole resultset with constant memory use) by iterating over the cursor, ie:
for row in cursor:
print row
Let's continue with your code:
row = rs
if int(row) == 1:
# ...
elif int(row) == 0:
# ...
The first line is useless - it only makes row an alias of rs, and badly named - it's not a "row" (one line of results from your query), it's an int. Since it's already an int, converting it to int is also useless. And finally, unless 'ipadress' is a unique key in your table, your query might return more than one row.
If what you want is the effective value(s) for the serialno field for records matching fromIP, you have to fetch the row(s):
row = cursor.fetchone() # first row, as a tuple
then get the value, which in this case will be the first item in row:
serialno = row[0]

How to check if record exists with Python MySQdb

Im creating a python program that connects to mysql.
i need to check if a table contains the number 1 to show that it has connected successfully, this is my code thus far:
xcnx.execute('CREATE TABLE settings(status INT(1) NOT NULL)')
xcnx.execute('INSERT INTO settings(status) VALUES(1)')
cnx.commit()
sqlq = "SELECT * FROM settings WHERE status = '1'"
xcnx.execute(sqlq)
results = xcnx.fetchall()
if results =='1':
print 'yep its connected'
else:
print 'nope not connected'
what have i missed? i am an sql noob, thanks guys.

I believe the most efficient "does it exist" query is just to do a count:
sqlq = "SELECT COUNT(1) FROM settings WHERE status = '1'"
xcnx.execute(sqlq)
if xcnx.fetchone()[0]:
# exists
Instead of asking the database to perform any count operations on fields or rows, you are just asking it to return a 1 or 0 if the result produces any matches. This is much more efficient that returning actual records and counting the amount client side because it saves serialization and deserialization on both sides, and the data transfer.
In [22]: c.execute("select count(1) from settings where status = 1")
Out[22]: 1L # rows
In [23]: c.fetchone()[0]
Out[23]: 1L # count found a match
In [24]: c.execute("select count(1) from settings where status = 2")
Out[24]: 1L # rows
In [25]: c.fetchone()[0]
Out[25]: 0L # count did not find a match
count(*) is going to be the same as count(1). In your case because you are creating a new table, it is going to show 1 result. If you have 10,000 matches it would be 10000. But all you care about in your test is whether it is NOT 0, so you can perform a bool truth test.
Update
Actually, it is even faster to just use the rowcount, and not even fetch results:
In [15]: if c.execute("select (1) from settings where status = 1 limit 1"):
print True
True
In [16]: if c.execute("select (1) from settings where status = 10 limit 1"):
print True
In [17]:
This is also how django's ORM does a queryObject.exists().

If all you want to do is check if you have successfully established a connection then why are you trying to create a table, insert a row, and then retrieve data from it?
You could simply do the following...
sqlq = "SELECT * FROM settings WHERE status = '1'"
xcnx.execute(sqlq)
results = xcnx.fetchone()
if results =='1':
print 'yep its connected'
else:
print 'nope not connected'
In fact if your program has not thrown an exception so far indicates that you have established the connection successfully. (Do check the code above, I'm not sure if fetchone will return a tuple, string, or int in this case).
By the way, if for some reason you do need to create the table, I would suggest dropping it before you exit so that your program runs successfully the second time.

When you run results = xcnx.fetchall(), the return value is a sequence of tuples that contain the row values. Therefore when you check if results == '1', you are trying to compare a sequence to a constant, which will return False. In your case, a single row of value 0 will be returned, so you could try this:
results = xcnx.fetchall()
# Get the value of the returned row, which will be 0 with a non-match
if results[0][0]:
print 'yep its connected'
else:
print 'nope not connected'
You could alternatively use a DictCursor (when creating the cursor, use .cursor(MySQLdb.cursors.DictCursor) which would make things a bit easier to interpret codewise, but the result is the same:
if results[0]['COUNT(*)]':
# Continues...
Also, not a big deal in this case, but you are comparing an integer value to a string. MySQL will do the type conversion, but you could use SELECT COUNT(*) FROM settings WHERE status = 1 and save a (very small) bit of processing.

I recently improved my efficiency by instead of querying select, just adding a primary index to the unique column and then adding it. MySQL will only add it if it doesn't exist.
So instead of 2 statements:
Query MySQL for exists:
Query MySQL insert data
Just do 1 and it will only work if it's unique:
Query MySQL insert data
1 Query is better than 2.

In Python what could cause a for loop to randomly go backwards in value?

What can cause an iterator to go forwards in a loop, and then backwards?
This is the code I'm using to loop through the table's primary key field. The primary key is being used to populate initial values in a separate table.
For loop:
for row in sampleDB.select_fromTable():
print row[0]
sampleDB.insert_toTable(row[0], 2.0)
sqllite insert statement:
def insert_toTable(self, primaryKey, initial):
c = self.conn.cursor()
c.execute('insert into insert_toTable VALUES(?, ?)', (primaryKey, initial))
if c.rowcount == 1:
print "Updated row.\n"
else:
print "Row does not exist.\n"
self.conn.commit()
c.close()
The select statement that creates the tuple to loop through:
def select_fromTable(self):
c = self.conn.cursor()
c.execute('select * from sampleTable')
c.close
return c
Here is an example table:
Primary Key Text
0 John
1 Sue
2 Bill
3 Tyler
Running the loop without the insert statement prints each unique key once, but if I add the call to the insert function (insert_toTable) I get this phenomenon:
0
Updated row.
1
Updated row.
0
Traceback (most recent call last):
sqlite3.IntegrityError: column urlid is not unique
The next iteration of the loop should be to the unique value "2" not back to "0"....
I can provide more sections of code if needed.

I suspect the results of this code may change depending on exactly which versions of sqlite and python are used.
Notice that your call to c.close in the select_fromTable method should be c.close(). This is a fortunate error, since you cannot iterate over the results of the query after the cursor is closed. However, the result is that you have two open cursors in the loop.
Try changing your select_fromTable method to:
def select_fromTable(self):
c = self.conn.cursor()
c.execute('select * from sampleTable')
results = c.fetchall()
c.close()
return results
and see what happens. I believe it will fix your problem.