description:
execute following stored procedure:

set ansi_nulls on
set quoted_identifier on
go

alter procedure [dbo].[ordersbyproductproc](@product varchar(50), @test int
output)
as
select count(*), productname from orderdetails, products 
where orderdetails.productcode = products.productcode 
and products.productname = @product group by products.productname;

select @test=count(*) from orderdetails;


build number: 2.6.0.v20100609-0630

expected result is 
1, @test = 2996 ( which equals to count(*)); 
2, @reture value = 0 
3, result set is retrieved successfully.

actual result:
1, when executing in stored procedure data set, @test = null 
2, when previewing output parameters, i got exceptions.

errorlog:
org.eclipse.birt.data.engine.odaconsumer.odadataexception: cannot execute the statement.
org.eclipse.birt.report.data.oda.jdbc.jdbcexception: sql statement does not return a resultset object.
sql error #1: procedure or function 'ordersbyproductproc' expects parameter '@product', which was not supplied.
;
java.sql.sqlexception: procedure or function 'ordersbyproductproc' expects parameter '@product', which was not supplied.
at org.eclipse.birt.data.engine.odaconsumer.exceptionhandler.newexception(exceptionhandler.java:52)
at org.eclipse.birt.data.engine.odaconsumer.exceptionhandler.throwexception(exceptionhandler.java:108)
at org.eclipse.birt.data.engine.odaconsumer.exceptionhandler.throwexception(exceptionhandler.java:84)
at org.eclipse.birt.data.engine.odaconsumer.preparedstatement.execute(preparedstatement.java:586)
at org.eclipse.birt.data.engine.executor.datasourcequery.execute(datasourcequery.java:765)
at org.eclipse.birt.data.engine.impl.preparedodadsquery$odadsqueryexecutor.executeodiquery(preparedodadsquery.java:427)
at org.eclipse.birt.data.engine.impl.queryexecutor.execute(queryexecutor.java:1045)
at org.eclipse.birt.data.engine.impl.serviceforqueryresults.executequery(serviceforqueryresults.java:232)
at org.eclipse.birt.data.engine.impl.queryresults.getresultiterator(queryresults.java:159)
at org.eclipse.birt.report.designer.data.ui.dataset.resultsetpreviewpage.populaterecords(resultsetpreviewpage.java:568)
at org.eclipse.birt.report.designer.data.ui.dataset.resultsetpreviewpage.access$5(resultsetpreviewpage.java:562)
at org.eclipse.birt.report.designer.data.ui.dataset.resultsetpreviewpage$5.run(resultsetpreviewpage.java:483)
at org.eclipse.jface.operation.modalcontext$modalcontextthread.run(modalcontext.java:121)
caused by: org.eclipse.birt.report.data.oda.jdbc.jdbcexception: sql statement does not return a resultset object.
sql error #1: procedure or function 'ordersbyproductproc' expects parameter '@product', which was not supplied.
;
java.sql.sqlexception: procedure or function 'ordersbyproductproc' expects parameter '@product', which was not supplied.
at org.eclipse.birt.report.data.oda.jdbc.callstatement.executequery(callstatement.java:438)
at org.eclipse.birt.report.data.oda.jdbc.callstatement.execute(callstatement.java:587)
at org.eclipse.datatools.connectivity.oda.consumer.helper.odaadvancedquery.doexecute(odaadvancedquery.java:123)
at org.eclipse.datatools.connectivity.oda.consumer.helper.odaadvancedquery.execute(odaadvancedquery.java:82)
at org.eclipse.birt.data.engine.odaconsumer.preparedstatement.execute(preparedstatement.java:570)
... 9 more
caused by: java.sql.sqlexception: procedure or function 'ordersbyproductproc' expects parameter '@product', which was not supplied.
at net.sourceforge.jtds.jdbc.sqldiagnostic.adddiagnostic(sqldiagnostic.java:367)
at net.sourceforge.jtds.jdbc.tdscore.tdserrortoken(tdscore.java:2217)
at net.sourceforge.jtds.jdbc.tdscore.nexttoken(tdscore.java:1696)
at net.sourceforge.jtds.jdbc.tdscore.getmoreresults(tdscore.java:522)
at net.sourceforge.jtds.jdbc.jtdsstatement.processresults(jtdsstatement.java:386)
at net.sourceforge.jtds.jdbc.jtdsstatement.executesql(jtdsstatement.java:369)
at net.sourceforge.jtds.jdbc.jtdspreparedstatement.execute(jtdspreparedstatement.java:426)
at org.eclipse.birt.report.data.oda.jdbc.callstatement.executequery(callstatement.java:402)
... 13 more
it works in my environment. i guess you do not input the required default value for the data set parameter @product. please check it again.
close the bug