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
/**
		 * @param band
		 *            the list band
		 */
		public void handleListingBand( BandDesign band, IBaseQueryDefinition query, boolean onGroup, IGroupDefinition groupDefn )
		{
			if ( band != null )
			{
				ArrayList subQueries = (ArrayList)( (ArrayList)query.getSubqueries( ) ).clone( );
				for ( int i = 0; i < band.getContentCount( ); i++ )
				{
					
					build( query, band.getContent( i ) );
				}
				ArrayList subQueriesChanged = (ArrayList)query.getSubqueries( );
				if ( subQueriesChanged != null )
				{
					for ( int i = 0; i < subQueriesChanged.size( ); i++ )
					{
						SubqueryDefinition subQuery = (SubqueryDefinition)subQueriesChanged.get( i );
						if ( !subQueries.contains( subQuery ) 
								&& subQuery instanceof SubqueryDefinition )
						{
							( (SubqueryDefinition)subQuery ).setApplyOnGroupFlag( onGroup );
							if ( groupDefn != null )
							{
								subQueriesChanged.remove( subQuery );
								groupDefn.getSubqueries( ).add( subQuery );
							}
						}