I have a problem getting the query results from my Python-Code. The connection to the database seems to work, but i always get the error:
"InterfaceError: No result set to fetch from."
Can somebody help me with my problem? Thank you!!!
cnx = mysql.connector.connect(
host="127.0.0.1" ,
user="root" ,
passwd="*****",
db="testdb"
)
cursor = cnx.cursor()
query = ("Select * from employee ;")
cursor.execute(query)
row = cursor.fetchall()
If your problem is still not solved, you can consider replacing the python mysql driver package and use pymysql.
You can write code like this
#!/usr/bin/python
import pymysql
db = pymysql.connect(host="localhost", # your host, usually localhost
user="test", # your username
passwd="test", # your password
db="test") # name of the data base
# you must create a Cursor object. It will let
# you execute all the queries you need
cur = db.cursor()
query = ("SELECT * FROM employee")
# Use all the SQL you like
cur.execute(query)
# print all the first cell of all the rows
for row in cur.fetchall():
print(row[0])
db.close()
This should be able to find the result you want
add this to your code
for i in row:
print(i)
you did not print anything which is why that's not working
this will print each row in separate line
first try to print(row),if it fails try to execute using the for the loop,remove the semicolon in the select query statement
cursor = connection.cursor()
rows = cursor.execute('SELECT * FROM [DBname].[dbo].TableName where update_status is null ').fetchall()
for row in rows:
ds = row[0]
state = row[1]
here row[0] represent the first columnname in the database
& row[1] represent the second columnname in the database & so on
Related
So currently when I execute SELECT query and retrieve data I have to get results like this:
connection = psycopg2.connect(user="admin",
password="admin",
host="127.0.0.1",
port="5432",
database="postgres_db")
cursor = connection.cursor()
cursor.execute("SELECT * FROM user")
users = cursor.fetchall()
for row in users:
print(row[0])
print(row[1])
print(row[2])
What I want to do is, use column names instead of integers, like this:
for row in users:
print(row["id"])
print(row["first_name"])
print(row["last_name"])
Is this possible, and if it is, then how to do it?
You need to use RealDictCursor, then you can access the results like a dictionary:
import psycopg2
from psycopg2.extras import RealDictCursor
connection = psycopg2.connect(user="...",
password="...",
host="...",
port="...",
database="...",
cursor_factory=RealDictCursor)
cursor = connection.cursor()
cursor.execute("SELECT * FROM user")
users = cursor.fetchall()
print(users)
print(users[0]['user'])
Output:
[RealDictRow([('user', 'dbAdmin')])]
dbAdmin
no need to call fetchall() method, the psycopg2 cursor is an iterable object you can directly do:
cursor.execute("SELECT * FROM user")
for buff in cursor:
row = {}
c = 0
for col in cursor.description:
row.update({str(col[0]): buff[c]})
c += 1
print(row["id"])
print(row["first_name"])
print(row["last_name"])
I am struggling to establish a connection inside data iteration. Means I am running a select query to postgres and iterating the return data. after some transformation I am writing it to another table. But it is not working. Sample python code is below.
conn = pgconn(------)
cursor = pgconn.Cursor()
query1 = "select * from table"
query2 = "select * from table2 where Id=(%s);"
cursor.execute(query1)
result = query1.fetchall()
for row in result:
If row.a == 2:
cursor.execute(query2, [row.time])
In the above python code I can't able to extract the data by running query2 and passing query1 result as a parameter. It seems cursor is blocked by the query1 so query2 execution is not happening. Please some one help in this issue.
First of all you can write a join statement to do this and can get the data easily
select * from table join table2 where table2.id == table.time
Also why this is not working maybe because the cursor object is getting override inside the for loop and thus the query results get changed.
Use RealDictCursor, and correct the syntax on your inside call to execute():
import psycopg2
import psycopg2.extras
conn = pgconn(------)
cursor = conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor)
query1 = "select * from table"
query2 = "select * from table2 where Id=(%s);"
cursor.execute(query1)
result = query1.fetchall()
for row in result:
If row.a == 2:
cursor.execute(query2, (row['time'],))
1. install psycopg2 and psycopg2.extras. ( pip install)
Then set up your Postgres Connection like:
def Postgres_init(self):
try:
conn = psycopg2.connect(host=os.environ['SD_POSTGRES_SERVER'],
user=os.environ['SD_POSTGRES_USER'],
password=os.environ['SD_POSTGRES_PASSWORD'],
port=os.environ['SD_POSTGRES_PORT'],
database=os.environ['SD_POSTGRES_DATABASE'])
logging.info("Connected to PostgreSQL")
except (Exception, psycopg2.Error) as error:
logging.info(error)
2. Connect your Cursor with the defined connection
cursor = conn.cursor()
3. Execute your query:
cursor.execute("""SELECT COUNT (column1) from tablename WHERE column2 =%s""", (
Value,)) # Check if already exists
result = cursor.fetchone()
Now the value is stored in the "result" variable. Now you can execute the next query like:
cursor.execute("""
INSERT INTO tablename2
(column1, column2, column3)
VALUES
(%s, %s, %s)
ON CONFLICT(column1) DO UPDATE
SET
column2=excluded.column2,
column3=excluded.column3;
""", (result, column2, column3)
)
Now the result of query 1 is stored in the second table in the first column.
Now you can close your connection:
conn.close()
I query a table then loop through it to Update another table.
The console Prints shows correct data.
Not sure how to debug the cursor.execute for the UPDATE query.
It is not updating on the table. It's not a permission issue. If I run update command on my SQL workbench it works fine.
cursor = conn.cursor()
cursor.execute("Select Account_Name FROM dsf_CS_WebAppView")
for row in cursor.fetchall():
try:
cursor.execute("Select fullpath FROM customerdesignmap WHERE
fullpath LIKE '%{}%'".format(row.Account_Name))
rows = cursor.fetchall()
print(len(cursor.fetchall()))
if len(rows) > 0:
for rowb in rows:
print(rowb.fullpath)
print(row.Account_Name)
if len(row.Account_Name) > 2:
cursor.execute("UPDATE customerdesignmap SET householdname = {}, msid = {} WHERE fullpath LIKE '{}'".format(row.Account_Name, row.UniqueProjectNumber, rowb.fullpath))
conn.commit()
except:
pass
Consider a pure SQL solution as SQL Server supports UPDATE and JOIN across multiple tables. This avoids the nested loops, cursor calls, and string formatting of SQL commands.
UPDATE m
SET m.householdname = v.Account_Name,
m.msid = v.UniqueProjectNumber
FROM customerdesignmap m
JOIN dsf_CS_WebAppView v
ON m.fullpath LIKE CONCAT('%', v.Account_Name, '%')
In Python, run above in a single cursor.execute() with commit() call.
cursor.execute('''my SQL Query''')
conn.commit()
I am trying to execute the following script. but I don't get neither the desired results nor a error message ,and I can't figure out where I'm doing wrong.
import pyodbc
cnxn = pyodbc.connect("Driver={SQL Server Native Client 11.0};"
"Server=mySRVERNAME;"
"Database=MYDB;"
"uid=sa;pwd=MYPWD;"
"Trusted_Connection=yes;")
cursor = cnxn.cursor()
cursor.execute('select DISTINCT firstname,lastname,coalesce(middlename,\' \') as middlename from Person.Person')
for row in cursor:
print('row = %r' % (row,))
any ideas ? any help is appreciated :)
You have to use a fetch method along with cursor. For Example
for row in cursor.fetchall():
print('row = %r' % (row,))
EDIT :
The fetchall function returns all remaining rows in a list.
If there are no rows, an empty list is returned.
If there are a lot of rows, *this will use a lot of memory.*
Unread rows are stored by the database driver in a compact format and are often sent in batches from the database server.
Reading in only the rows you need at one time will save a lot of memory.
If we are going to process the rows one at a time, we can use the cursor itself as an interator
Moreover we can simplify it since cursor.execute() always returns a cursor :
for row in cursor.execute("select bla, anotherbla from blabla"):
print row.bla, row.anotherbla
Documentation
I found this information useful to retrieve data from SQL database to python as a data frame.
import pandas as pd
import pymssql
con = pymssql.connect(server='use-et-aiml-cloudforte-aiops- db.database.windows.net',user='login_username',password='login_password',database='database_name')
cursor = con.cursor()
query = "SELECT * FROM <TABLE_NAME>"
cursor.execute(query)
df = pd.read_sql(query, con)
con.close()
df
import mysql.connector as mc
connection creation
conn = mc.connect(host='localhost', user='root', passwd='password')
print(conn)
#create cursor object
cur = conn.cursor()
print(cur)
cur.execute('show databases')
for i in cur:
print(i)
query = "Select * from employee_performance.employ_mod_recent"
emp_data = pd.read_sql(query, conn)
emp_data
I tried to fill a table in a database using MySQLdb. It did not give any errors, and once gave the warning
main.py:23: Warning: Data truncated for column 'other_id' at row 1
cur.execute("INSERT INTO map VALUES(%s,%s)",(str(info[0]).replace('\n',''), str(info[2].replace('\n','').replace("'",""))))
so I thought it was working fine. However, when it was finished and I did a row count it turned out that nothing was added. Why was the data not added to the database? The code is below
def fillDatabase():
db = MySQLdb.connect(host="127.0.0.1",
user="root",
passwd="",
db="uniprot_map")
cur = db.cursor()
conversion_file = open('idmapping.dat')
for line in conversion_file:
info = line.split('\t')
cur.execute("INSERT INTO map VALUES(%s,%s)",(str(info[0]).replace('\n',''), str(info[2].replace('\n','').replace("'",""))))
def test():
db = MySQLdb.connect(host="127.0.0.1",
user="root",
passwd="",
db="uniprot_map")
cur = db.cursor()
cur.execute("SELECT COUNT(*) FROM map")
rows = cur.fetchall()
for row in rows:
print row
def main():
fillDatabase()
test()
You need to do a db.commit() after adding all of the entries. Even if the update is not transactional, the DBAPI imposes an implicit transaction on every change.