NHibernate is primarily tested on Microsoft SQL Server 2000. It is also known to work on these databases:

Microsoft SQL Server 2005/2000

SQL Server 2005 and 2000 are the primary databases used by the developers of NHibernate.

Configuration example:

    
        NHibernate.Connection.DriverConnectionProvider
        NHibernate.Dialect.MsSql2005Dialect
        NHibernate.Driver.SqlClientDriver
        Server=(local);Initial Catalog=dbname;User Id=user;Password=********
    

For SQL Server 2000, change the dialect to NHibernate.Dialect.MsSql2000Dialect.

Issues

SQL Server sometimes ignores columns specified in ORDER BY clause of a query if they are not included in the SELECT clause. This behavior is actually valid according to the SQL standard, but may be surprising. For example, a query like this is not guaranteed to be ordered correctly:

from Person p order by p.Company.Name

Oracle

Oracle 9i and 10g are supported, both using Microsoft driver (System.Data.OracleClient) and using Oracle driver (Oracle.Data.OracleClient).

Issues

Microsoft's driver does not handle long character strings correctly. An error happens in some circumstances when using a string of length 2000-4000 as a parameter value.

Oracle cannot handle empty strings (""), you should use null instead. An IUserType implementation to perform the conversion is contained in Nullables.NHibernate library (part of NHibernateContrib package).

Microsoft Access

Microsoft Access has its own dialect and driver (contributed by Lukas Krejci).

They are currently in a separated library: NHibernate.JetDriver.dll (in NHibernateContrib package).

Here is what your hibernate.cfg.xml file should contain when using a Microsoft Access database:

    
        NHibernate.Connection.DriverConnectionProvider
        NHibernate.JetDriver.JetDialect, NHibernate.JetDriver
        NHibernate.JetDriver.JetDriver, NHibernate.JetDriver
        Provider=Microsoft.Jet.OLEDB.4.0;Data Source=YourDatabaseFilePathHere.mdb
    

Issues

There are still few problems with join syntax in queries that use more than one join. This driver passes 93% of NHibernate tests (there are 23 failing tests).

The most complete topic about these issues is here: Using NHibernate with Microsoft Access 2003 / Jet 4.0. JIRA issues NH-124 and NH-437 have some information on problems with implementing Microsoft Access dialect. You can also try searching NHibernate forum for "access jet" (require all words).

Firebird

Firebird is supported since version 1.5.3, though version 2.0.1 is strongly recommended. To work with Firebird, install the latest Firebird .NET Data Provider. If the data provider is installed in the GAC (the standard behavior of its installer), add this section to your application configuration file (App.config or Web.config):

    
                    fullName="FirebirdSql.Data.FirebirdClient, Version=2.0.1.0, Culture=neutral, PublicKeyToken=3750abcc3150b00c" />
    

The value of the fullName attribute will depend on the version of the assembly you have installed in the GAC.

Here is what your hibernate.cfg.xml file should contain when using Firebird:

    
        NHibernate.Connection.DriverConnectionProvider
        NHibernate.Driver.FirebirdClientDriver
        ReadCommitted
        
            Server=localhost;
            Database=C:\nhibernate.fdb;
            User=SYSDBA;Password=masterkey
        
        false
        NHibernate.Dialect.FirebirdDialect
        true
        444
        true 1, false 0, yes 1, no 0
    

All Firebird 2.0.1 embedded functions are registered in the dialect, as well as user-defined functions from ib_udf2.sql. These functions can be used in HQL queries.

PostgreSQL

PostgreSQL version 7.4 with latest Npgsql works almost perfectly. Later versions should work too.

Configuration example:

    
        NHibernate.Connection.DriverConnectionProvider
        NHibernate.Driver.NpgsqlDriver
        
            Server=localhost;initial catalog=nhibernate;User ID=nhibernate;Password=********;
        
        NHibernate.Dialect.PostgreSQLDialect
    

DB2 UDB

DB2 UDB is supported and reportedly even passes all the tests (see http://nhibernate.sourceforge.net/forum/viewtopic.php?t=73). Example configuration using the ODBC drivers that come with the 'stinger' release of db2:

    

        NHibernate.Connection.DriverConnectionProvider
        NHibernate.Driver.OdbcDriver
        driver={IBM DB2 ODBC DRIVER};Database=db;hostname=host;port=port;protocol=TCPIP; uid=uid; pwd=pwd
        true
        NHibernate.Dialect.DB2Dialect
        true

        

    
    

MySQL

All MySQL versions should work, though there are issues with zero dates (see below for details). To connect to your database use Connector/NET (formerly known as ByteFX.Data.MySqlClient).

Configuration example:

    
        NHibernate.Connection.DriverConnectionProvider
        NHibernate.Driver.MySqlDataDriver
        
            Database=test;Data Source=someip;User Id=blah;Password=blah
        
        NHibernate.Dialect.MySQLDialect
    

Issues

MySQL has a unique "feature" of allowing invalid dates in a DATE field, and especially using 0000-00-00 as a default value for DATE NOT NULL columns. When MySQL Connector encounters such a date, it either throws an exception or returns a non-standard MySqlDateTime object (depending on a connection string parameter) which throws an exception when converting itself to a DateTime.

Possible workarounds:

• avoid zero dates
• modify Connector/NET source code to round zero dates to DateTime.Min and back (see JIRA issue NH-32 for a patch to an older version of the Connector)
• create a user type for MySqlDateTime (no known implementations currently)

SQLite

SQLite version 3 works rather well using ADO.NET provider available from http://sourceforge.net/projects/adodotnetsqlite. NHibernate Query Analyzer uses SQLite (see [Related Projects]).

Configuration example:

    
        NHibernate.Connection.DriverConnectionProvider
        NHibernate.Driver.SQLiteDriver
        
            Data Source=nhibernate.db;Version=3
        
        NHibernate.Dialect.SQLiteDialect
        true=1;false=0
    

Issues

SQLite currently fails 17 tests out of approximately 500 in NHibernate test suite. Some of the failures are caused by SQLite being unable to store strings containing NUL characters, other tests fail because of a bug in SQLite ADO.NET provider when using a table with spaces in its name.