This can be easily achieved through a report

Hi can you please once rectify my code i was trying through scripting to achieve this

Try this

var ritm = new GlideRecord('sc_req_item');
ritm.addEncodedQuery('active=true^RLQUERYsc_task.request_item,=00^active=true^ENDRLQUERY');
ritm.query();
gs.print(ritm.getRowCount());
while(ritm.next()){
	gs.print(ritm.number);
}

can i not use glide aggregate?

What are you trying to accomplish exactly? What's the end goal once you have the aggregate count?