Conditional coalesce script for sys_id creates record

[SANJEEV4]

I have a scenario on multiple coalesce conditions. So I created coalesce on the sys_id field(script)

var gr = new GlideRecord("table");
gr.addQuery("field1", source.fieldA);
gr.query();
if (gr.next()) {
    return gr.sys_id;  // I tried with - answer = gr.sys_id;
} else {
var gr1 = new GlideRecord("table");
gr1.addQuery("field1", source.fieldB);
gr1.query();
if (gr1.next()) {
return gr1.sys_id; // I tried with - answer = gr1.sys_id;
} else{
   return null;     //I tried with :  return -1 (and) return GlideGuid.generate(null); (and) answer = -1
}
}

// Its not working 

 If It does not match, should not create a new record. for that, I created onBefore with 

if (action == 'insert') {
ignore = true;
}

Still creating new records. 

Thanks in advance 

[Mohith Devatte]

@SANJEEV4 so in the above code you can see i wrote a else loop which ignores the insertion

did you try then above method and got any luck of it ?