Using the update and delete method we can update & delete a single as well as multiple record.

Update list of record :

var gr = new GlideRecord('incident');
gr.addEncodedQuery('state=2^priority=5');
gr.query();
while(gr.next()){
	gr.assignment_group ="0a52d3dcd7011200f2d224837e6103f2";
	gr.update();
}

Update list of records with updateMultiple :

var gr = new GlideRecord('incident');
gr.addEncodedQuery('state=2^priority=5');
gr.query();
gr.assignment_group ="0a52d3dcd7011200f2d224837e6103f2";
gr.updateMultiple();

Delete records :

var gr = new GlideRecord('incident');
gr.addEncodedQuery('state=2^priority=5');
gr.query();
while(gr.next()){
	gr.assignment_group ="0a52d3dcd7011200f2d224837e6103f2";
	gr.deleteRecord();
}