Support for the Microsoft SQL Server database.
The MSSQL dialect will work with three different available drivers:
Drivers are loaded in the order listed above based on availability.
If you need to load a specific driver pass module_name when creating the engine:
engine = create_engine('mssql://dsn', module_name='pymssql')module_name currently accepts: pyodbc, pymssql, and adodbapi.
Currently the pyodbc driver offers the greatest level of compatibility.
Connecting with create_engine() uses the standard URL approach of mssql://user:pass@host/dbname[?key=value&key=value...].
If the database name is present, the tokens are converted to a connection string with the specified values. If the database is not present, then the host token is taken directly as the DSN name.
Examples of pyodbc connection string URLs:
mssql://mydsn - connects using the specified DSN named mydsn. The connection string that is created will appear like:
dsn=mydsn;TrustedConnection=Yesmssql://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:
dsn=mydsn;UID=user;PWD=pass
mssql://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:
dsn=mydsn;UID=user;PWD=pass;LANGUAGE=us_english
mssql://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://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://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:
mssql:///?odbc_connect=dsn%3Dmydsn%3BDatabase%3Ddb
would create the following connection string:
dsn=mydsn;Database=dbEncoding your connection string can be easily accomplished through the python shell. For example:
>>> import urllib
>>> urllib.quote_plus('dsn=mydsn;Database=db')
'dsn%3Dmydsn%3BDatabase%3Ddb'Additional arguments which may be specified either as query string arguments on the URL, or as keyword argument to create_engine() are:
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))
).create()would yield:
CREATE TABLE test (
id INTEGER NOT NULL IDENTITY(100,10) PRIMARY KEY,
name VARCHAR(20) NULL,
)
Note that the start and increment values for sequences are optional and will default to 1,1.
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:
select.limitwill yield:
SELECT TOP n
If the has_window_funcs flag is set then LIMIT with OFFSET support is available through the ROW_NUMBER OVER construct. This construct requires an ORDER BY to be specified as well and is only available on MSSQL 2005 and later.
MSSQL has support for three levels of column nullability. The default nullability allows nulls and is explicit in the CREATE TABLE construct:
name VARCHAR(20) NULL
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.
For MSSQL versions that support the DATE and TIME types (MSSQL 2008+) the data type is used. For versions that do not support the DATE and TIME types a DATETIME type is used instead and the MSSQL dialect handles converting the results properly. This means Date() and Time() are fully supported on all versions of MSSQL. If you do not desire this behavior then do not use the Date() or Time() types.
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.