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