So sorry, i have one sqlite file and it includes many tables(Like table_A to table_Z)
Sorry, i only can use the c.execute('SELECT ST_Name FROM table_A') and do table_B again.
How can i use the loop to do it, i already search all day, but i don't get the answer, please help me.
Thx!!
About my code, please refer below
import sqlite3
import numpy as np
Sqlite_Path = 'D:\Student.sqlite'
conn = sqlite3.connect(Sqlite_Path)
c = conn.cursor()
c.execute('SELECT ST_Name FROM Table_A')
data = c.fetchall()
# do something
c.execute('SELECT ST_Name FROM Table_B')
data = c.fetchall()
# do something again
This looks like a homework to me, but anyway:
tables = ["Table_A ", "Table_B", "Table_C"]
for table in tables:
c.execute('SELECT ST_Name FROM {}'.format(table))
data = c.fetchall()
# do something
If you don't know all the tables or for some other reason you can do something like this:
tables = [r[0] for r in db.execute('select name from sqlite_master where name like "table_%" and type = "table"')]
for table in tables:
stmt = 'SELECT * FROM {};'.format(table)
c = db.execute(stmt)
rows = c.fetch_all()
# ... do something with results
this returns ALL table names in your sqlitefile
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 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
I am using this sample sqlite database and my code is
import sqlite3
conn = sqlite3.connect('chinook.db')
conn.execute("SELECT * FROM tracks")
rows = conn.cursor().fetchall()
It should have worked, but rows is empty?
What am I doing wrong here?
The Connection.execute shortcut returns a cursor instance, which you need to use with fetchall. In your code, you're creating a new, independent cursor.
Thus:
import sqlite3
conn = sqlite3.connect('chinook.db')
cursor = conn.execute("SELECT * FROM tracks")
rows = cursor.fetchall()
or even shorter (not recommended, but for those who like obscured one-liners):
rows = sqlite3.connect('chinook.db').execute("SELECT * FROM tracks").fetchall()
Or don't use Connection.execute shortcut, to avoid confusion:
import sqlite3
conn = sqlite3.connect('chinook.db')
cursor = conn.cursor()
cursor.execute("SELECT * FROM tracks")
rows = cursor.fetchall()
I am trying to retrieve data from an SQL server using pyodbc and print it in a table using Python. However, I can only seem to retrieve the column name and the data type and stuff like that, not the actual data values in each row of the column.
Basically I am trying to replicate an Excel sheet that retrieves server data and displays it in a table. I am not having any trouble connecting to the server, just that I can't seem to find the actual data that goes into the table.
Here is an example of my code:
import pyodbc
cnxn = pyodbc.connect('DRIVER={SQL Server};SERVER=SQLSRV01;DATABASE=DATABASE;UID=USER;PWD=PASSWORD')
cursor = cnxn.cursor()
cursor.execute("SELECT * FROM sys.tables")
tables = cursor.fetchall()
#cursor.execute("SELECT WORK_ORDER.TYPE,WORK_ORDER.STATUS, WORK_ORDER.BASE_ID, WORK_ORDER.LOT_ID FROM WORK_ORDER")
for row in cursor.columns(table='WORK_ORDER'):
print row.column_name
for field in row:
print field
However the result of this just gives me things like the table name, the column names, and some integers and 'None's and things like that that aren't of interest to me:
STATUS_EFF_DATE
DATABASE
dbo
WORK_ORDER
STATUS_EFF_DATE
93
datetime
23
16
3
None
0
None
None
9
3
None
80
NO
61
So I'm not really sure where I can get the values to fill up my table. Would it should be in table='WORK_ORDER', but could it be under a different table name? Is there a way of printing the data that I am just missing?
Any advice or suggestions would be greatly appreciated.
You are so close!
import pyodbc
cnxn = pyodbc.connect('DRIVER={SQL Server};SERVER=SQLSRV01;DATABASE=DATABASE;UID=USER;PWD=PASSWORD')
cursor = cnxn.cursor()
cursor.execute("SELECT WORK_ORDER.TYPE,WORK_ORDER.STATUS, WORK_ORDER.BASE_ID, WORK_ORDER.LOT_ID FROM WORK_ORDER")
for row in cursor.fetchall():
print row
(the "columns()" function collects meta-data about the columns in the named table, as opposed to the actual data).
you could try using Pandas to retrieve information and get it as dataframe
import pyodbc as cnn
import pandas as pd
cnxn = pyodbc.connect('DRIVER={SQL Server};SERVER=SQLSRV01;DATABASE=DATABASE;UID=USER;PWD=PASSWORD')
# Copy to Clipboard for paste in Excel sheet
def copia (argumento):
df=pd.DataFrame(argumento)
df.to_clipboard(index=False,header=True)
tableResult = pd.read_sql("SELECT * FROM YOURTABLE", cnxn)
# Copy to Clipboard
copia(tableResult)
# Or create a Excel file with the results
df=pd.DataFrame(tableResult)
df.to_excel("FileExample.xlsx",sheet_name='Results')
I hope this helps!
Cheers!
In order to receive actual data stored in the table, you should use one of fetch...() functions or use the cursor as an iterator (i.e. "for row in cursor"...). This is described in the documentation:
cursor.execute("select user_id, user_name from users where user_id < 100")
rows = cursor.fetchall()
for row in rows:
print row.user_id, row.user_name
Just do this:
import pandas as pd
import pyodbc
cnxn = pyodbc.connect("Driver={SQL Server}\
;Server=SERVER_NAME\
;Database=DATABASE_NAME\
;Trusted_Connection=yes")
df = pd.read_sql("SELECT * FROM myTableName", cnxn)
df.head()
Instead of using the pyodbc library, use the pypyodbc library... This worked for me.
import pypyodbc
conn = pypyodbc.connect("DRIVER={SQL Server};"
"SERVER=server;"
"DATABASE=database;"
"Trusted_Connection=yes;")
cursor = conn.cursor()
cursor.execute('SELECT * FROM [table]')
for row in cursor:
print('row = %r' % (row,))
import pyodbc
conn = pyodbc.connect('Driver={SQL Server};'
'Server=db-server;'
'Database=db;'
'Trusted_Connection=yes;')
sql = "SELECT * FROM [mytable] "
cursor.execute(sql)
for r in cursor:
print(r)
Why pyodbc you can try with pymssql. For more information follow this link: https://stackoverflow.com/a/70445445/8614314.
import pandas as pd
import pymssql
con = pymssql.connect(<conncetion to the server and db>)
cursor = con.cursor()
query = "<Your query>"
cursor.execute(query)
df = pd.read_sql(query, con)
con.close()
Upvoted answer din't work for me, It was fixed by editing connection line as follows(replace semicolons with coma and also remove those quotes):
import pyodbc
cnxn = pyodbc.connect(DRIVER='{SQL Server}',SERVER=SQLSRV01,DATABASE=DATABASE,UID=USER,PWD=PASSWORD)
cursor = cnxn.cursor()
cursor.execute("SELECT WORK_ORDER.TYPE,WORK_ORDER.STATUS, WORK_ORDER.BASE_ID, WORK_ORDER.LOT_ID FROM WORK_ORDER")
for row in cursor.fetchall():
print row
How can I determine if a table exists using the Psycopg2 Python library? I want a true or false boolean.
How about:
>>> import psycopg2
>>> conn = psycopg2.connect("dbname='mydb' user='username' host='localhost' password='foobar'")
>>> cur = conn.cursor()
>>> cur.execute("select * from information_schema.tables where table_name=%s", ('mytable',))
>>> bool(cur.rowcount)
True
An alternative using EXISTS is better in that it doesn't require that all rows be retrieved, but merely that at least one such row exists:
>>> cur.execute("select exists(select * from information_schema.tables where table_name=%s)", ('mytable',))
>>> cur.fetchone()[0]
True
I don't know the psycopg2 lib specifically, but the following query can be used to check for existence of a table:
SELECT EXISTS(SELECT 1 FROM information_schema.tables
WHERE table_catalog='DB_NAME' AND
table_schema='public' AND
table_name='TABLE_NAME');
The advantage of using information_schema over selecting directly from the pg_* tables is some degree of portability of the query.
select exists(select relname from pg_class
where relname = 'mytablename' and relkind='r');
The first answer did not work for me. I found success checking for the relation in pg_class:
def table_exists(con, table_str):
exists = False
try:
cur = con.cursor()
cur.execute("select exists(select relname from pg_class where relname='" + table_str + "')")
exists = cur.fetchone()[0]
print exists
cur.close()
except psycopg2.Error as e:
print e
return exists
#!/usr/bin/python
# -*- coding: utf-8 -*-
import psycopg2
import sys
con = None
try:
con = psycopg2.connect(database='testdb', user='janbodnar')
cur = con.cursor()
cur.execute('SELECT 1 from mytable')
ver = cur.fetchone()
print ver //здесь наш код при успехе
except psycopg2.DatabaseError, e:
print 'Error %s' % e
sys.exit(1)
finally:
if con:
con.close()
I know you asked for psycopg2 answers, but I thought I'd add a utility function based on pandas (which uses psycopg2 under the hood), just because pd.read_sql_query() makes things so convenient, e.g. avoiding creating/closing cursors.
import pandas as pd
def db_table_exists(conn, tablename):
# thanks to Peter Hansen's answer for this sql
sql = f"select * from information_schema.tables where table_name='{tablename}'"
# return results of sql query from conn as a pandas dataframe
results_df = pd.read_sql_query(sql, conn)
# True if we got any results back, False if we didn't
return bool(len(results_df))
I still use psycopg2 to create the db-connection object conn similarly to the other answers here.
The following solution is handling the schema too:
import psycopg2
with psycopg2.connect("dbname='dbname' user='user' host='host' port='port' password='password'") as conn:
cur = conn.cursor()
query = "select to_regclass(%s)"
cur.execute(query, ['{}.{}'.format('schema', 'table')])
exists = bool(cur.fetchone()[0])
Expanding on the above use of EXISTS, I needed something to test table existence generally. I found that testing for results using fetch on a select statement yielded the result "None" on an empty existing table -- not ideal.
Here's what I came up with:
import psycopg2
def exist_test(tabletotest):
schema=tabletotest.split('.')[0]
table=tabletotest.split('.')[1]
existtest="SELECT EXISTS (SELECT 1 FROM information_schema.tables WHERE table_schema = '"+schema+"' AND table_name = '"+table+"' );"
print('existtest',existtest)
cur.execute(existtest) # assumes youve already got your connection and cursor established
# print('exists',cur.fetchall()[0])
return ur.fetchall()[0] # returns true/false depending on whether table exists
exist_test('someschema.sometable')
You can look into pg_class catalog:
The catalog pg_class catalogs tables and most everything else that has
columns or is otherwise similar to a table. This includes indexes (but
see also pg_index), sequences (but see also pg_sequence), views,
materialized views, composite types, and TOAST tables; see relkind.
Below, when we mean all of these kinds of objects we speak of
“relations”. Not all columns are meaningful for all relation types.
Assuming an open connection with cur as cursor,
# python 3.6+
table = 'mytable'
cur.execute(f"SELECT EXISTS(SELECT relname FROM pg_class WHERE relname = {table});")
if cur.fetchone()[0]:
# if table exists, do something here
return True
cur.fetchone() will resolve to either True or False because of the EXISTS() function.