PI to SQL Server works as of 7/29/2018. I am much better at MS SQL than Raspbian or Linux and the Pi, but it does work. Setting it up requires a little documentation from everywhere. Python 2 and Python 3 are both installed on the Pi for the newest Raspbian OS. You must be sure pyodbc is installed on Python 3 and the driver is setup and configured. If not, the first statement --> import pyodbc will fail.
Ok here is a good head start there are several components you will need.
is a great place to start.
After you go through their docs.
A note about /etc/odbcinst.ini file.
Below is a command to edit it easily.
sudo nano /etc/odbcinst.ini
Your drivers will located a different place for the PI in the odbcinst.ini file.
These were double checked this is where mine were installed.
Driver = /usr/lib/arm-linux-gnueabi/odbc/libtdsodbc.so
Setup = /usr/lib/arm-linux-gnueabi/odbc/libtdsS.so
This helped me get mine working.
Last minute change to get python 3 working and the next held me up a while
sudo apt-get install python3-pymysql
This last command fixed me.
sudo dpkg-reconfigure tdsodbc
These commands might help
After all this is done, hopefully you will be closer to yours working after this. I have it working with Python 2 and 3 and Tkinter. I also have it working on Windows IoT Core on the Pi. My little video shows the speed and that yes it can work very well, I just had to show it.
Again this is not the best way to access the database unless you have complete control of the network. You should use a Rest or Web Services process across the web. It is much more secure.
I will try and put all this together in a document when I can find time to try it from a fresh Pi Raspbian build.