Connecting to SQL Server 2012 using sqlalchemy and pyodbc

Question

I'm trying to connect to a SQL Server 2012 database using SQLAlchemy (with pyodbc) on Python 3.3 (Windows 7-64-bit). I am able to connect using straight pyodbc but have been unsuccessful at connecting using SQLAlchemy. I have dsn file setup for the database access.

I successfully connect using straight pyodbc like this:

con = pyodbc.connect('FILEDSN=c:\\users\\me\\mydbserver.dsn') 

For sqlalchemy I have tried:

import sqlalchemy as sa engine = sa.create_engine('mssql+pyodbc://c/users/me/mydbserver.dsn/mydbname') 

The create_engine method doesn't actually set up the connection and succeeds, but iIf I try something that causes sqlalchemy to actually setup the connection (like engine.table_names()), it takes a while but then returns this error:

DBAPIError: (Error) ('08001', '[08001] [Microsoft][ODBC SQL Server Driver][DBNETLIB]SQL Server does not exist or access denied. (17) (SQLDriverConnect)') None None

I'm not sure where thing are going wrong are how to see what connection string is actually being passed to pyodbc by sqlalchemy. I have successfully using the same sqlalchemy classes with SQLite and MySQL.

Thanks in advance!

Answer 1

The file-based DSN string is being interpreted by SQLAlchemy as server name = c, database name = users.

I prefer connecting without using DSNs, it's one less configuration task to deal with during code migrations.

This syntax works using Windows Authentication:

engine = sa.create_engine('mssql+pyodbc://server/database') 

Or with SQL Authentication:

engine = sa.create_engine('mssql+pyodbc://user:password@server/database') 

SQLAlchemy has a thorough explanation of the different connection string options here.

Answer 2

In Python 3 you can use function quote_plus from module urllib.parse to create parameters for connection:

import urllib params = urllib.parse.quote_plus("DRIVER={SQL Server Native Client 11.0};"                                  "SERVER=dagger;"                                  "DATABASE=test;"                                  "UID=user;"                                  "PWD=password")  engine = sa.create_engine("mssql+pyodbc:///?odbc_connect={}".format(params)) 

In order to use Windows Authentication, you want to use Trusted_Connection as parameter:

params = urllib.parse.quote_plus("DRIVER={SQL Server Native Client 11.0};"                                  "SERVER=dagger;"                                  "DATABASE=test;"                                  "Trusted_Connection=yes") 

In Python 2 you should use function quote_plus from library urllib instead:

params = urllib.quote_plus("DRIVER={SQL Server Native Client 11.0};"                            "SERVER=dagger;"                            "DATABASE=test;"                            "UID=user;"                            "PWD=password")