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Execute a multi-select SQL query using pyodbc

I'm trying to execute a multi-select SQL query using Pyodbc, but getting errors either about no results or no scalar variables. Since I need to create SQL variables that are used at different locations in the query, how could I get this to run in pyodbc?
Would this be feasible if I converted my SQL into a stored procedure?
It is not likely that I will be able to create the logic as a stored procedure as I do not have write access to the database.
Is there any possible way to get this type of query to run in python, or does it need to be modified in some way?
| ID | LNAME | FNAME | EMAIL |
| ----- | -------- | -------- | ------- |
| 1 | Smith | Bob | s#a.com |
| 2 | Davidson | Mike | d#a.com |
| 1 | Campbell | Brian | c#a.com |
This is what I tried so far but keep running into errors.
q = """
set ANSI_WARNINGS OFF;
declare #html varchar(MAX)
decalre #dedupedemails varchar(MAX)
decalre #esc_seq int
set #esc_seq = 5;
if object_id('tempdb.dbo.##dedupemail', 'U') is not null
drop table ##dedupemail;
with sub1 as (
select p.ID, p.LNAME, p.FNAME, p.EMAIL
from dbo.person p
),
sub2 as (
select
s1.*,
case when s1.ID = 1
then 'Yes'
else 'No'
end as IS_ADMIN
from sub1 s1
)
select distinct s2.* into ##dedupemail
from sub2 s2
where s2.IS_ADMIN = 'Yes'
set #html = 'abc';
select #dedupedemails = ltrim(stuff((
select '; ' + d.email
from ##dedupemail d
for xml path('')), 1,1,''));
select #dedupedemails as EMAIL_LIST, #html as EMAIL_BODY"""
try:
cnxn = pyodbc.connect(cnxn_str)
cursor = cnxn()
cursor.execute(q)
result = cursor.fetchall()
del cnxn
except pyodbc.Error as e:
print("Error caught: ", e)
The error:
Error caught: No results. Previous SQL was not a query.
Another error that I get refers to unknown scalars, but it always gives errors.

MySQL connector Python variables not registering

I'm currently using the mysql-connector-python package to execute database actions on Flask. It's been working so well until suddenly the variables don't seem to working correctly anymore. My code is here:
#bp.route('/addcart', methods=('OPTIONS', 'POST'))
def addcart():
...
userID = session.get("user_id")
reqDict = request.get_json()
itemCode = str(reqDict['itemCode'])
itemAmt = reqDict['itemAmt']
if userID is not None:
db = get_db()
cursor = db.cursor()
query = ('SELECT %s FROM cartdata WHERE id = %s')
cursor.execute(query, (itemCode, userID))
currentNum = cursor.fetchone()[0]
if currentNum is None:
stmt = ('UPDATE cartdata SET %s = 1 WHERE id = %s')
cursor.execute(stmt, (itemCode, userID))
else:
currentNum = int(currentNum) + int(itemAmt)
stmt = ('UPDATE cartdata SET %s = %s WHERE id = %s')
cursor.execute(stmt, (itemCode, currentNum, userID))
....
For some reason, I seem to having trouble with the itemCode variable. When I use it properly, like in the execution of 'query' or 'stmt', it doesn't work. Typically I will get an error saying
" 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 ''p1' = 1 WHERE id = 21'".
However, if I do this:
query = ('SELECT ' + itemCode + ' FROM cartdata WHERE id = %s')
...
stmt = ('UPDATE cartdata SET '+ itemCode +' = 1 WHERE id = %s')
...
It works properly as intended.
EDIT: I've checked my backend, and apparently the UPDATE statement does not actually update anything. So now I'm at a complete loss.
I don't understand why the connector suddenly breaks now for variables. I've checked this variables and its types, but they were the expected types. Any insight would be helpful.
My table schema for 'cartdata' looks something like this:
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| id | int(11) | NO | PRI | NULL | |
| p1 | int(8) | YES | | NULL | |
| p2 | int(8) | YES | | NULL | |
| p3 | int(8) | YES | | NULL | |
| p4 | int(8) | YES | | NULL | |
| p5 | int(8) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+

That's because when MySQL connector injects your variables into the SQL statement, it formats them according to their type.
You can actually see it in the error message that you get:
"p1' = 1 WHERE id = 21'"
^
So probably, your SQL query looks like this:
SELECT 'p1' FROM cartdata WHERE id = someId
Which is syntactically invalid SQL...
Your second option however seems okay. Btw, it seems weird to adapt the column you want to select depending on the user's input... I'd highly recommend to validate this value with something efficient...
Details
You cannot use %s for column names since this injects a string value in your SQL query and this results in a non valid SQL syntax (column names are not string values).
As above:
SET %s = ...
Generates:
SET 'colName' = ...
which is not valid because you are attempting to affect a value to another value...
That would be the same as trying to do the following in python:
'foo' = 'bar'
or
'foo' = 4
You can use %s when setting values (using SET colName = %s) or filtering values (using WHERE colName = %s) because the type of the values in the column colName is actually a string.
As above:
WHERE colName = %s
Generates:
WHERE colName = 'fooBar'
which is valid because you filter on the values that are equal to the string fooBar.
By the way, you might want to check what
SELECT %s FROM cartdata WHERE id = %s
gives you as a result. That could result problems... Actually MySQL won't tell you anything, but you result will probably be exactly the value of itemCode. (it is valid SQL SELECT 'hello', it just returns 'hello').

How to pass id from flask app to mysql database

I have a flask application that is connected to the MySQL database.
NOTE
database name = evaluation
table name = evaluation
columns = eval_id, eval_name, date
I have an 'evaluation table' with field eval_id, eval_name and date in it.
mysql> use evaluation;
mysql> describe evaluation;
+-----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| eval_id | int(11) | NO | PRI | NULL | |
| eval_name | varchar(20) | NO | | NULL | |
| date | datetime(6) | NO | | NULL | |
+-----------+-------------+------+-----+---------+-------+
How can I write an API to get a particular evaluation by its id?
I tried the below, but it doesn't work.
#app.route('/getEval/<int:eval_id>', methods=['GET'])
def getEvalByID(eval_id):
cur.execute('''select * from evaluation.evaluation where eval_id=eval_id''')
res = cur.fetchall()
return jsonify({'test':str(res)})
How can I correct this and get only the evaluation based on the eval_id mentioned in the app.route.

You need to place the eval_id not as String but as a VAR.
#app.route('/getEval/<int:eval_id>', methods=['GET'])
def getEvalByID(eval_id):
cur.execute('select * from evaluation.evaluation where eval_id=' + str(eval_id))
res = cur.fetchall()
return jsonify({'test':str(res)})

try with cur.execute('select * from evaluation.evaluation where eval_id={}'.format(eval_id))

Using MySQLdb to return values - Python

I have a table called coords and it is defined as:
mysql> describe coords;
+-----------+--------------+------+-----+------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+--------------+------+-----+------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| location | varchar(150) | NO | UNI | NULL | |
| latitude | float(20,14) | YES | | 0.00000000000000 | |
| longitude | float(20,14) | YES | | 0.00000000000000 | |
-----------------------------------------------------------------------------
I am using the MySQLdb import in my Python script. The purpose of this table is to store (as you can guess, but for clarity) location coordinates (but only when I do not have the coordinates already for a particular location).
I will be querying this table in my Python program to see if I already have coordinates for a pre-requested location. I'm doing this to speed up the use of the geopy package that interrogates Google's Geolocation Service.
How do I store the returned floats that correspond to a location? So far I have the following:
myVar = cur.execute("SELECT latitude, longitude FROM coords WHERE location ='" + jobLocation + "';")
if myVar == 1:
print(cur.fetchone())
else:
try:
_place, (_lat, _lon) = geos.geocode(jobLocation, region='GB', exactly_one=False)
print("%s: %.5f, %.5f" % _place, (_lat, _lon))
except ValueError as err:
print(err)
The code works (well, not really...) but I have no idea of how to get the returned coordinates into separate float variables.
Can you help?

When you do cur.fetchone(), you need to store the result somewhere:
row = cur.fetchone()
print row[0], row[1]
Now row[0] will contain the latitude, and row[1] the longitude.
If you do this when connecting:
cur = con.cursor(mdb.cursors.DictCursor)
you can then use a dictionary to refer to the columns by name:
row = cur.fetchone()
print row["latitude"], row["longitude"]

MySQL Python Insert strange?

I dont see why it's not working. I have created several databases and tables and obviously no problem. But I am stuck with this table which is created from django data model. To clarify what I have done, created new database and table from mysql console and try to insert from python and working. But, this one is strange for me.
class Experiment(models.Model):
user = models.CharField(max_length=25)
filetype = models.CharField(max_length=10)
createddate= models.DateField()
uploaddate = models.DateField()
time = models.CharField(max_length=20)
size = models.CharField(max_length=20)
located= models.CharField(max_length=50)
Here is view in mysql console
mysql> describe pmass_experiment;
+-------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| user | varchar(25) | NO | | NULL | |
| filetype | varchar(10) | NO | | NULL | |
| createddate | date | NO | | NULL | |
| uploaddate | date | NO | | NULL | |
| time | varchar(20) | NO | | NULL | |
| size | varchar(20) | NO | | NULL | |
| located | varchar(50) | NO | | NULL | |
+-------------+-------------+------+-----+---------+----------------+
8 rows in set (0.01 sec)
Above pmass_experiment table is created by django ORM after python manage.py syncdb
Now I am trying to insert data into pmass_experiment through python MySQLdb
import MySQLdb
import datetime,time
import sys
conn = MySQLdb.connect(
host="localhost",
user="root",
passwd="root",
db="experiment")
cursor = conn.cursor()
user='tchand'
ftype='mzml'
size='10MB'
located='c:\'
date= datetime.date.today()
time = str(datetime.datetime.now())[10:19]
#Insert into database
sql = """INSERT INTO pmass_experiment (user,filetype,createddate,uploaddate,time,size,located)
VALUES (user, ftype, date, date, time, size, located)"""
try:
# Execute the SQL command
cursor.execute(sql)
# Commit your changes in the database
conn.commit()
except:
# Rollback in case there is any error
conn.rollback()
# disconnect from server
conn.close()
But, unfortunately nothing is inserting. I am guessing it's may be due to primary_key (id) in table which is not incrementing automatically.
mysql> select * from pmass_experiment;
Empty set (0.00 sec)
can you simply point out my mistake?
Thanks

sql = """INSERT INTO pmass_experiment (user,filetype,createddate,uploaddate,time,size,located)
VALUES (user, ftype, date, date, time, size, located)"""
Parametrize your sql and pass in the values as the second argument to cursor.execute:
sql = """INSERT INTO pmass_experiment (user,filetype,createddate,uploaddate,time,size,located)
VALUES (%s, %s, %s, %s, %s, %s, %s)"""
try:
# Execute the SQL command
cursor.execute(sql,(user, ftype, date, date, time, size, located))
# Commit your changes in the database
conn.commit()
except Exception as err:
# logger.error(err)
# Rollback in case there is any error
conn.rollback()
It is a good habit to always parametrize your sql since this will help prevent sql injection.
The original sql
INSERT INTO pmass_experiment (user,filetype,createddate,uploaddate,time,size,located)
VALUES (user, ftype, date, date, time, size, located)
seems to be valid. An experiment in the mysql shell shows it inserts a row of NULL values:
mysql> insert into foo (first,last,value) values (first,last,value);
Query OK, 1 row affected (0.00 sec)
mysql> select * from foo order by id desc;
+-----+-------+------+-------+
| id | first | last | value |
+-----+-------+------+-------+
| 802 | NULL | NULL | NULL |
+-----+-------+------+-------+
1 row in set (0.00 sec)
So I'm not sure why your are not seeing any rows committed to the database table.
Nevertheless, the original sql is probably not doing what you intend.