Bug 177504 Engine doesn't provide SubQuery for extended item
Engine doesn't provide SubQuery for extended item, so chart can't use container's binding to execute the query. If possible, engine could provide an option for extended item to choose whether engine could create the query, so extended item won't create SubQuery by itself.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/data/dte/ReportQueryBuilder.java
.prepareTotalExpressions( expressions, groupName );
				
				addNewColumnBindings( query, totalExpressionBinding );
				
				List newExpressions = totalExpressionBinding.getNewExpression( );
				return (String) newExpressions.get( 0 );
			}
			return expr;
		}			
		
		/**
		 * Transfer the old visibility and hightlight expressions to column dataBinding and bind
		 * it to the Query. And create new visibility and hightlight expressions to replace
		 * the old.
		 */
		private void transformColumnExpressions( ColumnDesign column,
				IBaseQueryDefinition query, String groupName )
		{
			if ( query == null )
			{
				return;
			}
			List expressions = new ArrayList( );
			VisibilityDesign visibilities = column.getVisibility( );
			if ( visibilities != null )
			{
				
				for ( int i = 0; i < visibilities.count( ); i++ )
				{
					expressions