I'm trying to execute an SQL stored procedure which does some inserts an updates, and I pass a parameter called lcLogSessionId to it. During the execution of the procedure this parameter is set to 1 if there are errors, and remains to 0 if everything worked correctly.
In my python script I need to retrieve that value at the end of the execution of the stored procedure.
This is my code:
stored_proc = "Exec [APP].[dataImport] #lcLogSessionId = %s"%(0)
conn = pyodbc.connect(connection_string, autocommit = True)
cursor = conn.cursor()
cursor.execute(stored_proc)
I've tried to fetch the cursor with row = cursor.fetchone(), but i get an error which says "No results. Previous SQL was not a query".
Is there a way to get the value of lcLogSessionId?
pyodbc does not currently implement the optional .callproc() method, so a workaround is required to retrieve output parameters and return values. For SQL Server that involves an anonymous code block to EXEC the stored procedure and then SELECT the values, e.g.,
sql = """\
DECLARE #out nvarchar(max);
EXEC [dbo].[test_for_pyodbc] #param_in = ?, #param_out = #out OUTPUT;
SELECT #out AS the_output;
"""
params = ("Burma!", )
crsr.execute(sql, params)
rows = crsr.fetchall()
while rows:
print(rows)
if crsr.nextset():
rows = crsr.fetchall()
else:
rows = None
More details at the pyodbc wiki:
https://github.com/mkleehammer/pyodbc/wiki/Calling-Stored-Procedures#output-parameters-and-return-values
Related
I am inserting JSON data into a MySQL database
I am parsing the JSON and then inserting it into a MySQL db using the python connector
Through trial, I can see the error is associated with this piece of code
for steps in result['routes'][0]['legs'][0]['steps']:
query = ('SELECT leg_no FROM leg_data WHERE travel_mode = %s AND Orig_lat = %s AND Orig_lng = %s AND Dest_lat = %s AND Dest_lng = %s AND time_stamp = %s')
if steps['travel_mode'] == "pub_tran":
travel_mode = steps['travel_mode']
Orig_lat = steps['var_1']['dep']['lat']
Orig_lng = steps['var_1']['dep']['lng']
Dest_lat = steps['var_1']['arr']['lat']
Dest_lng = steps['var_1']['arr']['lng']
time_stamp = leg['_sent_time_stamp']
if steps['travel_mode'] =="a_pied":
query = ('SELECT leg_no FROM leg_data WHERE travel_mode = %s AND Orig_lat = %s AND Orig_lng = %s AND Dest_lat = %s AND Dest_lng = %s AND time_stamp = %s')
travel_mode = steps['travel_mode']
Orig_lat = steps['var_2']['lat']
Orig_lng = steps['var_2']['lng']
Dest_lat = steps['var_2']['lat']
Dest_lng = steps['var_2']['lng']
time_stamp = leg['_sent_time_stamp']
cursor.execute(query,(travel_mode, Orig_lat, Orig_lng, Dest_lat, Dest_lng, time_stamp))
leg_no = cursor.fetchone()[0]
print(leg_no)
I have inserted higher level details and am now searching the database to associate this lower level information with its parent. The only way to find this unique value is to search via the origin and destination coordinates with the time_stamp. I believe the logic is sound and by printing the leg_no immediately after this section, I can see values which appear at first inspection to be correct
However, when added to the rest of the code, it causes subsequent sections where more data is inserted using the cursor to fail with this error -
raise errors.InternalError("Unread result found.")
mysql.connector.errors.InternalError: Unread result found.
The issue seems similar to MySQL Unread Result with Python
Is the query too complex and needs splitting or is there another issue?
If the query is indeed too complex, can anyone advise how best to split this?
EDIT As per #Gord's help, Ive tried to dump any unread results
cursor.execute(query,(leg_travel_mode, leg_Orig_lat, leg_Orig_lng, leg_Dest_lat, leg_Dest_lng))
leg_no = cursor.fetchone()[0]
try:
cursor.fetchall()
except mysql.connector.errors.InterfaceError as ie:
if ie.msg == 'No result set to fetch from.':
pass
else:
raise
cursor.execute(query,(leg_travel_mode, leg_Orig_lat, leg_Orig_lng, leg_Dest_lat, leg_Dest_lng, time_stamp))
But, I still get
raise errors.InternalError("Unread result found.")
mysql.connector.errors.InternalError: Unread result found.
[Finished in 3.3s with exit code 1]
scratches head
EDIT 2 - when I print the ie.msg, I get -
No result set to fetch from
All that was required was for buffered to be set to true!
cursor = cnx.cursor(buffered=True)
The reason is that without a buffered cursor, the results are "lazily" loaded, meaning that "fetchone" actually only fetches one row from the full result set of the query. When you will use the same cursor again, it will complain that you still have n-1 results (where n is the result set amount) waiting to be fetched. However, when you use a buffered cursor the connector fetches ALL rows behind the scenes and you just take one from the connector so the mysql db won't complain.
I was able to recreate your issue. MySQL Connector/Python apparently doesn't like it if you retrieve multiple rows and don't fetch them all before closing the cursor or using it to retrieve some other stuff. For example
import mysql.connector
cnxn = mysql.connector.connect(
host='127.0.0.1',
user='root',
password='whatever',
database='mydb')
crsr = cnxn.cursor()
crsr.execute("DROP TABLE IF EXISTS pytest")
crsr.execute("""
CREATE TABLE pytest (
id INT(11) NOT NULL AUTO_INCREMENT,
firstname VARCHAR(20),
PRIMARY KEY (id)
)
""")
crsr.execute("INSERT INTO pytest (firstname) VALUES ('Gord')")
crsr.execute("INSERT INTO pytest (firstname) VALUES ('Anne')")
cnxn.commit()
crsr.execute("SELECT firstname FROM pytest")
fname = crsr.fetchone()[0]
print(fname)
crsr.execute("SELECT firstname FROM pytest") # InternalError: Unread result found.
If you only expect (or care about) one row then you can put a LIMIT on your query
crsr.execute("SELECT firstname FROM pytest LIMIT 0, 1")
fname = crsr.fetchone()[0]
print(fname)
crsr.execute("SELECT firstname FROM pytest") # OK now
or you can use fetchall() to get rid of any unread results after you have finished working with the rows you retrieved.
crsr.execute("SELECT firstname FROM pytest")
fname = crsr.fetchone()[0]
print(fname)
try:
crsr.fetchall() # fetch (and discard) remaining rows
except mysql.connector.errors.InterfaceError as ie:
if ie.msg == 'No result set to fetch from.':
# no problem, we were just at the end of the result set
pass
else:
raise
crsr.execute("SELECT firstname FROM pytest") # OK now
cursor.reset() is really what you want.
fetchall() is not good because you may end up moving unnecessary data from the database to your client.
The problem is about the buffer, maybe you disconnected from the previous MySQL connection and now it cannot perform the next statement. There are two ways to give the buffer to the cursor. First, only to the particular cursor using the following command:
import mysql.connector
cnx = mysql.connector.connect()
# Only this particular cursor will buffer results
cursor = cnx.cursor(buffered=True)
Alternatively, you could enable buffer for any cursor you use:
import mysql.connector
# All cursors created from cnx2 will be buffered by default
cnx2 = mysql.connector.connect(buffered=True)
cursor = cnx.cursor()
In case you disconnected from MySQL, the latter works for you.
Enjoy coding
If you want to get only one result from a request, and want after to reuse the same connexion for other requests, limit your sql select request to 1 using "limit 1" at the end of your request.
ex "Select field from table where x=1 limit 1;"
This method is faster using "buffered=True"
Set the consume_results argument on the connect() method to True.
cnx = mysql.connector.connect(
host="localhost",
user="user",
password="password",
database="database",
consume_results=True
)
Now instead of throwing an exception, it basically does fetchall().
Unfortunately this still makes it slow, if you have a lot of unread rows.
There is also a possibility that your connection to MySQL Workbench is disconnected. Establish the connection again. This solved the problem for me.
cursor.reset()
and then create tables and load entries
Would setting the cursor within the for loop, executing it, and then closing it again in the loop help?
Like:
for steps in result['routes'][0]['legs'][0]['steps']:
cursor = cnx.cursor()
....
leg_no = cursor.fetchone()[0]
cursor.close()
print(leg_no)
I have a php script that executes a python script and returns the data back and it is stored in mysql. It's working fine but when the data is stored in the database it inserts an additional blank row. My question would be, how could I make so that it stores only the actual data I recieve.
This is part of the python script
##ser.write(sync)
ser.write(counters)
a = ser.read(30)
state = binascii.hexlify(a)
asd = re.sub(rb'([0-9, a-z, A-Z])(?!$)', rb'\1,', state)
url = 'http://127.0.0.1/sastest/meters.php'
x = requests.post(url, data = asd)
print(asd)
And this is from the PHP
passthru("meters.py");
$incomingData = file_get_contents("php://input");
$qry1 = "INSERT INTO machtest(data)
values('".$incomingData."')";
mysqli_query($conn,$qry1);
From comments we discover the overall process:
When I call meters.php it activates meters.py. meters.py interrogates a devices and sends the data back to meters.php
Because PHP's passthru does not support output return but a similar function exec does as array object with each line as elements, use that instead and do not have Python post back a response. Of course, always run parameterization when interacting with databases and passing input values.
Python (meters.py)
ser.write(counters)
a = ser.read(30)
state = binascii.hexlify(a)
asd = re.sub(rb'([0-9, a-z, A-Z])(?!$)', rb'\1,', state)
print(asd)
PHP (meters.php)
// USE output ARG
exec(command = "meters.py", output = $incomingData);
// USE PARAMETERIZATION
$qry = "INSERT INTO machtest (data) VALUES (%s)";
$stmt = mysqli_prepare($qry);
mysqli_stmt_bind_param($stmt, "s", $incomingData[0]);
mysqli_stmt_execute($stmt);
See mysqli prepared statement docs
Alternatively, have Python run all processing including device and database interaction. Then, have PHP call the .py script:
Python (meters.py)
import mysql.connector # USE ANY MySQL DB-API. THIS IS AN EXAMPLE
...
### INTERROGATE DEVICE
ser.write(counters)
a = ser.read(30)
state = binascii.hexlify(a)
asd = re.sub(rb'([0-9, a-z, A-Z])(?!$)', rb'\1,', state)
### APPEND TO DATABASE
# OPEN CONNECTION AND CURSOR
conn = mysql.connector.connect(host='localhost', database='mydatabase',
user='root', password='pwd')
cur = conn.cursor()
# USE PARAMETERIZATION
qry = "INSERT INTO machtest (data) VALUES (%s)"
cur.execute(qry, (asd,))
conn.commit()
cur.close()
conn.close()
See MySQL cursor execute docs
PHP (meters.php)
// NO NEED FOR output
passthru(command = "meters.py");
I have a Python application, in which I'm calling a MySQL stored procedure from my view, like so:
import mysql.connector
proc = 'audit_report'
parms = [data['schoolid'], dateToISO(data['startdatedefault'],'from'), dateToISO(data['enddatedefault'],'to'), joinIntList(data['studypgms'], joinWith), joinIntList(data['fedpgms'], joinWith), joinIntList(data['statuses'], joinWith), data['fullssndefault']]
conn = mysql.connector.connect(user='usr', database='db', password='pwd')
cursor = conn.cursor(dictionary=True)
cursor.callproc(proc, parms)
for result in cursor.stored_results():
print(result.fetchall())
I am getting the data returned as a list of tuples, the standard output. Since I'm using connector version 2.1.7, the docs say adding
dictionary=True
to the cursor declaration should cause the rowset to be returned as a list of dictionaries, with column name as the key of each dictionary. Main difference between my application and the example in the docs is that I'm using cursor.callproc(), whereas the examples use cursor.execute() with actual sql code.
I tried
print(cursor.column_names)
to see if I could get the column names that way, but all I get is
('#_audit_report_arg1', '#_audit_report_arg2', '#_audit_report_arg3', '#_audit_report_arg4', '#_audit_report_arg5', '#_audit_report_arg6', '#_audit_report_arg7')
which looks more like the input parameters to the stored procedure.
Is there any way to actually get the column names of the returned data? The procedure is somewhat complex and contains crosstab-type manipulation, but calling the same stored procedure from MySQL Workbench happily supplies the column names.
Normally, knowing what the output is supposed to be, I could hard-code column names, except this procedure crosstabs the data for the last few columns, and it is unpredictable what they will be until after the query runs.
Thanks...
You can use pymysql in python3 and it should work fine !!
import pymysql.cursors
connection = pymysql.connect(host='',
user='',
password='',
db='test',
charset='utf8mb4',
cursorclass=pymysql.cursors.DictCursor)
try:
with connection.cursor() as cursor:
# Read a single record
sql = "query"
cursor.execute(sql)
result = cursor.fetchone()
num_fields = len(cursor.description)
field_names = [i[0] for i in cursor.description]
print (field_names)
finally:
connection.close()
I am trying to fetch data from AWS MariaDB:
cursor = self._cnx.cursor()
stmt = ('SELECT * FROM flights')
cursor.execute(stmt)
print(cursor.rowcount)
# prints 2
for z in cursor:
print(z)
# Does not iterate
row = cursor.fetchone()
# row is None
rows = cursor.fetchall()
# throws 'No result set to fetch from.'
I can verify that table contains data using MySQL Workbench. Am I missing some step?
EDIT: re 2 answers:
res = cursor.execute(stmt)
# res is None
EDIT:
I created new Python project with a single file:
import mysql.connector
try:
cnx = mysql.connector.connect(
host='foobar.rds.amazonaws.com',
user='devuser',
password='devpasswd',
database='devdb'
)
cursor = cnx.cursor()
#cursor = cnx.cursor(buffered=True)
cursor.execute('SELECT * FROM flights')
print(cursor.rowcount)
rows = cursor.fetchall()
except Exception as exc:
print(exc)
If I run this code with simple cursor, fetchall raises "No result set to fetch from". If I run with buffered cursor, I can see that _rows property of cursor contains my data, but fetchall() returns empty array.
Your issue is that cursor.execute(stmt) returns an object with results and you're not storing that.
results = cursor.execute(stmt)
print(results.fetchone()) # Prints out and pops first row
For the future googlers with the same Problem I found a workaround which may help in some cases:
I didn't find the source of the problem but a solution which worked for me.
In my case .fetchone() also returned none whatever I did on my local(on my own Computer) Database. I tried the exact same code with the Database on our companies server and somehow it worked. So I copied the complete server Database onto my local Database (by using database dumps) just to get the server settings and afterwards I also could get data from my local SQL-Server with the code which didn't work before.
I am a SQL-newbie but maybe some crazy setting on my local SQL-Server prevented me from fetching data. Maybe some more experienced SQL-user knows this setting and can explain.
I have the following python code, it reads through a text file line by line and takes characters x to y of each line as the variable "Contract".
import os
import pyodbc
cnxn = pyodbc.connect(r'DRIVER={SQL Server};CENSORED;Trusted_Connection=yes;')
cursor = cnxn.cursor()
claimsfile = open('claims.txt','r')
for line in claimsfile:
#ldata = claimsfile.readline()
contract = line[18:26]
print(contract)
cursor.execute("USE calms SELECT XREF_PLAN_CODE FROM calms_schema.APP_QUOTE WHERE APPLICATION_ID = "+str(contract))
print(cursor.fetchall())
When including the line cursor.fetchall(), the following error is returned:
Programming Error: Previous SQL was not a query.
The query runs in SSMS and replace str(contract) with the actual value of the variable results will be returned as expected.
Based on the data, the query will return one value as a result formatted as NVARCHAR(4).
Most other examples have variables declared prior to the loop and the proposed solution is to set NO COUNT on, this does not apply to my problem so I am slightly lost.
P.S. I have also put the query in its own standalone file without the loop to iterate through the file in case this was causing the problem without success.
In your SQL query, you are actually making two commands: USE and SELECT and the cursor is not set up with multiple statements. Plus, with database connections, you should be selecting the database schema in the connection string (i.e., DATABASE argument), so TSQL's USE is not needed.
Consider the following adjustment with parameterization where APPLICATION_ID is assumed to be integer type. Add credentials as needed:
constr = 'DRIVER={SQL Server};SERVER=CENSORED;Trusted_Connection=yes;' \
'DATABASE=calms;UID=username;PWD=password'
cnxn = pyodbc.connect(constr)
cur = cnxn.cursor()
with open('claims.txt','r') as f:
for line in f:
contract = line[18:26]
print(contract)
# EXECUTE QUERY
cur.execute("SELECT XREF_PLAN_CODE FROM APP_QUOTE WHERE APPLICATION_ID = ?",
[int(contract)])
# FETCH ROWS ITERATIVELY
for row in cur.fetchall():
print(row)
cur.close()
cnxn.close()