Sets the current active database on the server that's associated with the
specified link identifier. Every subsequent call to
mysql_query() will be made on the active database.
The name of the database that is to be selected.
The MySQL connection. If the
link identifier is not specified, the last link opened by
mysql_connect() is assumed. If no such link is found, it
will try to create one as if mysql_connect() was called
with no arguments. If by chance no connection is found or established, an
E_WARNING level warning is generated.