mssql_select_db() sets the current active database on the server that's associated with the specified link identifier. If no link identifier is specified, the last opened link is assumed. If no link is open, the function will try to establish a link as if mssql_connect() was called, and use it.
Every subsequent call to mssql_query() will be made on the active database.
To escape the name of a database that contains spaces, hyphens ("-"), or any other exceptional characters, the database name must be enclosed in brackets, as is shown in the example, below. This technique must also be applied when selecting a database name that is also a reserved word (such as "primary").
$conn = mssql_connect('MYSQLSERVER', 'sa', 'password');
mssql_select_db('[my data-base]', $conn);