Add db_datareader and db_datawriter roles to a user for a database.

USE [dbname]
GO

/****** Object:  User [domain\user]    Script Date: 05/26/2011 05:37:39 ******/
IF  EXISTS (SELECT * FROM sys.database_principals WHERE name = N’domain\user’)
DROP USER [domain\user]
GO

USE [dbname]
GO

/****** Object:  User [domain\user]    Script Date: 05/26/2011 05:37:39 ******/
GO

CREATE USER [domain\user] FOR LOGIN [domain\user] WITH DEFAULT_SCHEMA=[dbo]
GO

EXEC sp_addrolemember N’db_datareader’, N’domain\user’
EXEC sp_addrolemember N’db_datawriter’, N’domain\user’

GO