Access azure sql database within iotedge module

Question

I have successfully query azure sql database on raspberry(through ssh) and other ides on my laptop.
My code:
import pymssql
conn = pymssql.connect(server='t***r.database.windows.net', user='@', password='', database=')
cursor = conn.cursor()
cursor.execute('SELECT * FROM Persons')
for row in cursor:
print ("Inserted Product ID : " +str(row))
print("done")
conn.close()

However, same piece of codes when i added to the SampleModule and deployed to iotedge device(raspberry) made my SampleModule stuck in backoff state(others were running normally). When i inspected the logs, i found this error: (20002, b'DB-Lib error message 20002, severity 9:\nAdaptive Server connection failed (***.database.windows.net:1433)\nNet-Lib error during Connection timed out (110)\n')

What i have done before the error:

• i have run successfully SampleModule without the above piece of codes before
• i have binded port 1433
• i set azure sql server firewall 0.0.0.0 to 255.255.255.255 for testing purpose so i doubt it is the problem
• In dockerfile, i only added RUN apt-get --assume-yes update and everything was smooth until the module actually ran on my raspberry
  RUN apt-get --assume-yes install freetds-dev freetds-bin gcc
  RUN pip install pymssql