[Solved] Connect to Oracle database using SQLALCHEMY
I am able to successfully connect to a sqlite database and access a particular table using the set of commands below.
from sqlalchemy import create_engine, MetaData, Table, and_
from sqlalchemy.sql import select
from pandas import DataFrame
db = create_engine('sqlite:///path\database.db')
metadata = MetaData(db)
table = Table('table name', metadata, autoload=True)
I am able to fetch data from an oracle database using cx_Oracle library.
However, when i try to connect to an Oracle Database in sqlalchemy, i am getting the following error
NoSuchTableError: <table name>
I have used the following commands:
db = create_engine('oracle://username:[email protected]:1521/instance name',echo='debug')
md = MetaData(bind=db)
t = Table('table name', md, autoload=True,schema='schema name')
When i use the following command
t= Table('table name', md, autoload=True,oracle_resolve_synonyms=True)
I get the following error:
AssertionError: There are multiple tables visible to the schema, you must specify owner
Can you please understand where exactly am i going wrong.
Thanks,
Rohit
Solution #1:
from sqlalchemy import create_engine
import cx_Oracle
host=hostname
port=port
sid='sid'
user='username'
password='password'
sid = cx_Oracle.makedsn(host, port, sid=sid)
cstr = 'oracle://{user}:{password}@{sid}'.format(
user=user,
password=password,
sid=sid
)
engine = create_engine(
cstr,
convert_unicode=False,
pool_recycle=10,
pool_size=50,
echo=True
)
result = engine.execute('select * from TABLE')
for row in result:
print row
This worked for me. A connection object can also be created like
conn = engine.connect()
conn.close()
which will enable to close the connection. This works even if you have a tunnel to your remote DB from your local port.
Solution #2:
You don’t need to import cx_Oracle anymore. The newer version of the sqlalchemy module calls the function cx_Oracle.makedsn(). Have a look:
from sqlalchemy.engine import create_engine
DIALECT = 'oracle'
SQL_DRIVER = 'cx_oracle'
USERNAME = 'your_username' #enter your username
PASSWORD = 'your_password' #enter your password
HOST = 'subdomain.domain.tld' #enter the oracle db host url
PORT = 1521 # enter the oracle port number
SERVICE = 'your_oracle_service_name' # enter the oracle db service name
ENGINE_PATH_WIN_AUTH = DIALECT + '+' + SQL_DRIVER + '://' + USERNAME + ':' + PASSWORD +'@' + HOST + ':' + str(PORT) + '/?service_name=" + SERVICE
engine = create_engine(ENGINE_PATH_WIN_AUTH)
#test query
import pandas as pd
test_df = pd.read_sql_query("SELECT * FROM global_name', engine)
Solution #3:
Assuming you have the Oracle client on your machine with a valid tnsnames.ora file, this works for me:
from sqlalchemy import create_engine
import pandas as pd
engine = create_engine('oracle://myusername:[email protected]')
con = engine.connect()
outpt = con.execute("SELECT * FROM YOUR_TABLE")
df = pd.DataFrame(outpt.fetchall())
df.columns = outpt.keys()
print(df.head())
con.close()
Solution #4:
This works for me, when there is no tnsnames.ora file.
user = 'system'
pwd = 'oracle'
dsn = cx_Oracle.makedsn(
'192.168.1.105', 49161,
# service_name="your_service_name_if_any"
)
ora_engine = create_engine(f'oracle+cx_oracle://{user}:{pwd}@{dsn}', echo=True)
ora_engine.connect()