Describe the bug

Problem

When reflecting a SQL Server table that uses the built-in SYSNAME type, SQLAlchemy does not recognize the type and emits a warning:

Did not recognize type 'SYSNAME' of column 'name'

The column is then reflected as NullType, which can break downstream operations such as type genericization or DDL generation.

Observed behavior

• Warning is emitted:
  Did not recognize type 'SYSNAME' of column 'name'
• Column is reflected as NullType

Expected behavior

SYSNAME should be recognized by the MSSQL dialect and mapped appropriately (it is a built-in alias for NVARCHAR(128)), so that:

• no warning is emitted
• reflection produces a usable SQLAlchemy type (not NullType)

Notes

• SYSNAME is a built-in SQL Server type commonly used in system objects and can also be used in user-defined tables.
• This issue affects standard reflection workflows and can lead to failures when performing operations like .as_generic() or create_all() on reflected metadata.

Optional link from https://docs.sqlalchemy.org which documents the behavior that is expected

No response

SQLAlchemy Version in Use

2.0.42

DBAPI (i.e. the database driver)

pyodbc

Database Vendor and Major Version

Microsoft SQL Server (tested on SQL Server 2022)

Python Version

3.13.11

Operating system

Windows

To Reproduce

from sqlalchemy import create_engine, Table, MetaData, Column
from sqlalchemy.types import UserDefinedType

engine = create_engine(
    "mssql+pyodbc://scott:tiger@localhost/test?"
    "driver=ODBC+Driver+18+for+SQL+Server&TrustServerCertificate=yes"
)

class SYSNAME(UserDefinedType):
    cache_ok = True
    def get_col_spec(self, **kw):
        return "SYSNAME"

with engine.connect() as conn:
    metadata = MetaData()

    t = Table("test_sysname", metadata, Column("name", SYSNAME))
    t.create(conn)

    # reflection
    Table("test_sysname", MetaData(), autoload_with=conn)

Error

SAWarning: Did not recognize type 'SYSNAME' of column 'name'

Additional context

No response