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Postgres connection in python

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()

Python and MySQL - fetchall() doesn't show any result

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

cursor.execute returns 1 int

When running a query to a mysql database using MySqlHook, cursor.execute(query) returns int 1
My code is
import logging
from airflow.hooks.mysql_hook import MySqlHook
query = "SELECT col1, col2 FROM myschema.mytable LIMIT 1"
mysql = MySqlHook(mysql_conn_id=conn_id)
conn = mysql.get_conn()
cursor = conn.cursor()
result_cursor = cursor.execute(query)
logging.info(result_cursor) # this prints out "INFO - 1" in the log
df = pd.DataFrame(result_cursor.fetchall(), columns=result_cursor.keys()) # this triggers error "ERROR - 'int' object has no attribute 'fetchall'"
I would have expected result_cursor to return a "fetchable" result, since the query is working fine.

Cursor.execute() return value is not defined by the db-api spec, but for most implementations it returns the number of rows affected by the query.
To retrieve data, you have to either iterate over the cursor or call .fetchall().

It seems I cannot save cursor.execute(query) into variable result_cursor.
To make the code work, I simply needed to define the data for the data-frame as cursor.fetchall()
cursor.execute(query)
df = pd.DataFrame(list(cursor.fetchall()), column=[col[0] for col in cursor.description])

pyodbc not updating table

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()

Inserting rows while fetching(from another table) in SQLite

I'm getting this error no matter what with python and sqlite.
File "addbooks.py", line 77, in saveBook
conn.commit()
sqlite3.OperationalError: cannot commit transaction - SQL statements in progress
The code looks like this:
conn = sqlite3.connect(fname)
cread = conn.cursor()
cread.execute('''select book_text from table''')
while True:
row = cread.fetchone()
if row is None:
break
....
for entry in getEntries(doc):
saveBook(entry, conn)
Can't do a fetchall() because table and column size are big, and the memory is scarce.
What can be done without resorting to dirty tricks(as getting the rowids in memory, which would probably fit, and then selecting the rows one by one)?.

The problem is that you've left the connection in auto-commit mode. Wrap a single transaction around the whole lot so that a commit only happens after you've done all the updates, and it should all work fine.

Don't know if this count as "dirty tricks" too ;-)
My solution to this problem is to use SELECT... LIMIT clause, assumed you have primary key integer field id
current_id = 0
while True:
cread.execute('''select book_text from table where id > %s limit 2''' % current_id)
results = cread.fetchall()
if results is None:
break;
for row in results:
... (save book) ...
current_id = row.id

The problem is that there should be no more than a single active cursor for a connection.
The solution is to use a new connection for the updates.
Unfortunatelly I do not remember the exact place in docs where I read it, so I can not prove it.
UPD:
The following code works on my Windows XP:
import sqlite3
import os
conn1 = sqlite3.connect('test.db')
cursor1 = conn1.cursor()
conn2 = sqlite3.connect('test.db')
cursor2 = conn2.cursor()
cursor1.execute("CREATE TABLE my_table (a INT, b TEXT)")
cursor1.executemany("INSERT INTO my_table (a, b) VALUES (?, NULL);", zip(range(5)))
conn1.commit()
cursor1.execute("SELECT * FROM my_table")
for a, b in cursor1:
cursor2.execute("UPDATE my_table SET b='updated' WHERE a = ?", (a, ))
conn2.commit()
print "results:"
print 10 * '-'
cursor1.execute("SELECT * FROM my_table")
for a, b in cursor1:
print a, b
cursor1.close()
conn1.close()
cursor2.close()
conn2.close()
os.unlink('test.db')
And returns the following as expected:
results:
----------
0 updated
1 updated
2 updated
3 updated
4 updated
If I move the conn2.commit() into the for loop, I get the same error as you mention:
Traceback (most recent call last):
File "concurent.py", line 16, in <module>
conn2.commit()
sqlite3.OperationalError: database is locked
Thus, the solution is to commit once at the end instead of committing after each line.