SQLAlchemy 0.6.1 Documentation

Version: 0.6.1 Last Updated: 07/25/2016 21:14:41
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Microsoft SQL Server

Support for the Microsoft SQL Server database.


See the individual driver sections below for details on connecting.

Auto Increment Behavior

IDENTITY columns are supported by using SQLAlchemy schema.Sequence() objects. In other words:

Table('test', mss_engine,
       Column('id', Integer,
              Sequence('blah',100,10), primary_key=True),
       Column('name', String(20))

would yield:

  name VARCHAR(20) NULL,

Note that the start and increment values for sequences are optional and will default to 1,1.

Implicit autoincrement behavior works the same in MSSQL as it does in other dialects and results in an IDENTITY column.

  • Support for SET IDENTITY_INSERT ON mode (automagic on / off for INSERT s)
  • Support for auto-fetching of @@IDENTITY/@@SCOPE_IDENTITY() on INSERT

Collation Support

MSSQL specific string types support a collation parameter that creates a column-level specific collation for the column. The collation parameter accepts a Windows Collation Name or a SQL Collation Name. Supported types are MSChar, MSNChar, MSString, MSNVarchar, MSText, and MSNText. For example:

Column('login', String(32, collation='Latin1_General_CI_AS'))

will yield:

login VARCHAR(32) COLLATE Latin1_General_CI_AS NULL


MSSQL has no support for the LIMIT or OFFSET keysowrds. LIMIT is supported directly through the TOP Transact SQL keyword:


will yield:


If using SQL Server 2005 or above, LIMIT with OFFSET support is available through the ROW_NUMBER OVER construct. For versions below 2005, LIMIT with OFFSET usage will fail.


MSSQL has support for three levels of column nullability. The default nullability allows nulls and is explicit in the CREATE TABLE construct:


If nullable=None is specified then no specification is made. In other words the database’s configured default is used. This will render:

name VARCHAR(20)

If nullable is True or False then the column will be NULL` or ``NOT NULL respectively.

Date / Time Handling

DATE and TIME are supported. Bind parameters are converted to datetime.datetime() objects as required by most MSSQL drivers, and results are processed from strings if needed. The DATE and TIME types are not available for MSSQL 2005 and previous - if a server version below 2008 is detected, DDL for these types will be issued as DATETIME.

Compatibility Levels

MSSQL supports the notion of setting compatibility levels at the database level. This allows, for instance, to run a database that is compatibile with SQL2000 while running on a SQL2005 database server. server_version_info will always retrun the database server version information (in this case SQL2005) and not the compatibiility level information. Because of this, if running under a backwards compatibility mode SQAlchemy may attempt to use T-SQL statements that are unable to be parsed by the database server.

Known Issues

  • No support for more than one IDENTITY column per table


Support for MS-SQL via pyodbc.

pyodbc is available at:



Examples of pyodbc connection string URLs:

  • mssql+pyodbc://mydsn - connects using the specified DSN named mydsn. The connection string that is created will appear like:

  • mssql+pyodbc://user:pass@mydsn - connects using the DSN named mydsn passing in the UID and PWD information. The connection string that is created will appear like:

  • mssql+pyodbc://user:pass@mydsn/?LANGUAGE=us_english - connects using the DSN named mydsn passing in the UID and PWD information, plus the additional connection configuration option LANGUAGE. The connection string that is created will appear like:

  • mssql+pyodbc://user:pass@host/db - connects using a connection string dynamically created that would appear like:

    DRIVER={SQL Server};Server=host;Database=db;UID=user;PWD=pass
  • mssql+pyodbc://user:pass@host:123/db - connects using a connection string that is dynamically created, which also includes the port information using the comma syntax. If your connection string requires the port information to be passed as a port keyword see the next example. This will create the following connection string:

    DRIVER={SQL Server};Server=host,123;Database=db;UID=user;PWD=pass
  • mssql+pyodbc://user:pass@host/db?port=123 - connects using a connection string that is dynamically created that includes the port information as a separate port keyword. This will create the following connection string:

    DRIVER={SQL Server};Server=host;Database=db;UID=user;PWD=pass;port=123

If you require a connection string that is outside the options presented above, use the odbc_connect keyword to pass in a urlencoded connection string. What gets passed in will be urldecoded and passed directly.

For example:


would create the following connection string:


Encoding your connection string can be easily accomplished through the python shell. For example:

>>> import urllib
>>> urllib.quote_plus('dsn=mydsn;Database=db')


Support for MS-SQL via mxODBC.

mxODBC is available at:


This was tested with mxODBC 3.1.2 and the SQL Server Native Client connected to MSSQL 2005 and 2008 Express Editions.


Connection is via DSN:


Execution Modes

mxODBC features two styles of statement execution, using the cursor.execute() and cursor.executedirect() methods (the second being an extension to the DBAPI specification). The former makes use of the native parameter binding services of the ODBC driver, while the latter uses string escaping. The primary advantage to native parameter binding is that the same statement, when executed many times, is only prepared once. Whereas the primary advantage to the latter is that the rules for bind parameter placement are relaxed. MS-SQL has very strict rules for native binds, including that they cannot be placed within the argument lists of function calls, anywhere outside the FROM, or even within subqueries within the FROM clause - making the usage of bind parameters within SELECT statements impossible for all but the most simplistic statements. For this reason, the mxODBC dialect uses the “native” mode by default only for INSERT, UPDATE, and DELETE statements, and uses the escaped string mode for all other statements. This behavior can be controlled completely via execution_options() using the native_odbc_execute flag with a value of True or False, where a value of True will unconditionally use native bind parameters and a value of False will uncondtionally use string-escaped parameters.


Support for the pymssql dialect.

This dialect supports pymssql 1.0 and greater.

pymssql is available at:



Sample connect string:


Adding “?charset=utf8” or similar will cause pymssql to return strings as Python unicode objects. This can potentially improve performance in some scenarios as decoding of strings is handled natively.


pymssql inherits a lot of limitations from FreeTDS, including:

  • no support for multibyte schema identifiers
  • poor support for large decimals
  • poor support for binary fields
  • poor support for VARCHAR/CHAR fields over 255 characters

Please consult the pymssql documentation for further information.

zxjdbc Notes

Support for the Microsoft SQL Server database via the zxjdbc JDBC connector.

JDBC Driver

Requires the jTDS driver, available from: http://jtds.sourceforge.net/


URLs are of the standard form of mssql+zxjdbc://user:pass@host:port/dbname[?key=value&key=value...].

Additional arguments which may be specified either as query string arguments on the URL, or as keyword arguments to create_engine() will be passed as Connection properties to the underlying JDBC driver.


The adodbapi dialect is not implemented for 0.6 at this time.

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