return null;
return expression;
	private String getColumnName( String expression )	{		for ( Iterator iter = columnList.iterator( ); iter.hasNext( ); )		{			ResultSetColumnHandle cachedColumn = (ResultSetColumnHandle) iter.next( );			if ( DEUtil.getExpression( cachedColumn ).equals( expression ) )			{				return cachedColumn.getColumnName( );			}		}		return null;	}