I have a postgres db running on docker. I am able to access this db via my sql client Dbeaver and when I run select statements I see the expected results.
I would like to be able to query this db via a Python script and after some searching found psycopg2 package.
When I run the code below it 'looks' like it's successful, the conn and cursor objects appear as a variables.
import pandas as pd
import psycopg2
# connect to db
conn = psycopg2.connect(
host="localhost",
database="postgres",
user="postgres",
password="example")
# create a cursor
cur = conn.cursor()
However, when trying to query the db using cur.connect(), , variable ex_data is None. This exact same query via my sql client returns a table of data.
ex_data = cur.execute('select * from myschema.blah limit 10;')
How can I query my db via Python using psycopg2? Desired result wold be a data frame with the result set from the query string above.
Related
I am trying to establish a connection to the impala database through a Python script using a keytab instead the normal user/password combination, but am unable to find any tutorials online whatsoever, the code I am currently using is:
conn = connect(host=impala_host, port=impala_port, use_ssl=True, auth_mechanism="PLAIN", user=username, password=pwd, database=impala_db)
cursor = conn.cursor()
However, I want to connect using keytab instead of my password.
It appears that you are trying to use that library: https://github.com/cloudera/impyla
Please have a look at Usage section in README.md there:
from impala.dbapi import connect
conn = connect(host='my.host.com', port=21050)
cursor = conn.cursor()
cursor.execute('SELECT * FROM mytable LIMIT 100')
print cursor.description # prints the result set's schema
results = cursor.fetchall()
...
...
I am creating a Python script to interact with schema permissions (and relative tables) on Redshift. As suggested in some other StackOverflow posts I am using psycopg2 library.
When I try to execute some simple SELECT FROM queries I have no problems: I can execute and see results with no issues.
Problem comes when for example I try to create a new schema or granting / revoking permissions. This kind of queries don't look like to produce any effect.
Here I show a very simple example in which I attempt to create a new schema:
conn_string = "dbname='{}' port='{}' host='{}' user='{}' password='{}'".format(DB_NAME, DB_PORT, DB_HOST, DB_USER, DB_PWD)
con = psycopg2.connect(conn_string)
sql = "CREATE SCHEMA new_schema"
cur = con.cursor()
cur.execute(sql)
But when I look into the Redshift DB I don't see any new schema called new_schema. Same behaviour happens when I try to run some permission grant / revoke query.
Anyone knows what is going on?
You have to commit the transaction.
con = psycopg2.connect(conn_string)
sql = "CREATE SCHEMA new_schema"
cur = con.cursor()
cur.execute(sql)
con.commit()
I'm using Visual Studio 2017 with a Python Console environment. I have a MySQL database set up which I can connect to successfully. I can also Insert data into the DB. Now I'm trying to display/fetch data from it.
I connect fine, and it seems I'm fetching data from my database, but nothing is actually printing to the console. I want to be able to fetch and display data, but nothing is displaying at all.
How do I actually display the data I select?
#importing module Like Namespace in .Net
import pypyodbc
#creating connection Object which will contain SQL Server Connection
connection = pypyodbc.connect('Driver={SQL Server};Server=DESKTOP-NJR6F8V\SQLEXPRESS;Data Source=DESKTOP-NJR6F8V\SQLEXPRESS;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=True;ApplicationIntent=ReadWrite;MultiSubnetFailover=False')
cursor = connection.cursor()
SQLCommand = ("SELECT ID FROM MyAI_DB.dbo.WordDefinitions WHERE ID > 117000")
#Processing Query
cursor.execute(SQLCommand)
#Commiting any pending transaction to the database.
connection.commit()
#closing connection
#connection.close()
I figured it out. I failed to include the right Print statement. Which was:
print(cursor.fetchone())
I also had the connection.commit statement in the wrong place (it was inserted even executing the Print statement). The final code that worked was this:
#importing module Like Namespace in .Net
import pypyodbc
#creating connection Object which will contain SQL Server Connection
connection = pypyodbc.connect('Driver={SQL Server};Server=DESKTOP-NJR6F8V\SQLEXPRESS;Data Source=DESKTOP-NJR6F8V\SQLEXPRESS;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=True;ApplicationIntent=ReadWrite;MultiSubnetFailover=False')
cursor = connection.cursor()
SQLCommand = ("SELECT * FROM MyAI_DB.dbo.WordDefinitions")
#Processing Query
cursor.execute(SQLCommand)
#Commiting any pending transaction to the database.
print(cursor.fetchone())
connection.commit()
#closing connection
#connection.close()
I'm using the Python package MySQLdb to fetch data from a MySQL database. However, I notice that I can't fetch the entirety of the data.
import MySQLdb
db = MySQLdb.connect(host=host, user=user, passwd=password)
cur = db.cursor()
query = "SELECT count(*) FROM table"
cur.execute(query)
This returns a number less than what I get if I execute the exact same query in MySQL Workbench. I've noticed that the data it doesn't return is the data that was inserted into the database most recently. Where am I going wrong?
You are not committing the inserted rows on the other connection.
I am testing Python and Mysql in that i am able to create and delete table's but i am unable to insert data in them.I searched stackoverflow and mostly they suggest to use
commit()
So i used it and even after i used the data is not inserted into the database.Please help me.
This is the code i use it creates the table but not inserting data
import MySQLdb
db = MySQLdb.connect("localhost","user","password")
cxn = MySQLdb.connect(db='test')
cursor = cxn.cursor()
cursor.execute("CREATE TABLE users(name VARCHAR(40),id VARCHAR(40))")
cursor.execute("INSERT INTO users(name,id) VALUES('John','1')")
db.commit()
print "Opertion completed successfully"
Are db and cxn connections to the same database?
You should establish your connection using following:
db = MySQLdb.connect(host="localhost",
db="test",
user="user",
passwd="password")
The cursor should then be derived from this connection via:
cursor = db.cursor()
I would hazard that your issue is coming from the ambiguity between db and cxn.