SQLAlchemy on Azure SQL Database

SQLAlchemy reaches Azure SQL Database through a dialect whose generated SQL differs from every other backend in one specific way, and almost every surprise here traces back to it. Every Python block below was verified on 2026-09-03 against SQLAlchemy 2.0.52 and pyodbc 5.3.0 and its output quoted verbatim; the version boundary below was measured the same day against 2.0.8, 2.0.9 and 2.0.10. Engine error numbers are from Microsoft Learn.

The dialect is named mssql and that name belongs only in the URL scheme. Everywhere else the product is Azure SQL Database, and an agent that adopts the dialect name has begun giving advice for a different product with different limits.

The engine URL

import os
from sqlalchemy import create_engine
from sqlalchemy.engine import URL