Laravel UNION联合查询并分页:
Union：对两个结果集进行并集操作，不包括重复行，同时进行默认规则的排序；
Union All：对两个结果集进行并集操作，包括重复行，不进行排序；
$xk =  DB::table('xiaokes')->select(['id','xk_name as name','xk_teacher_id as tid','ke_type','created_at']) 
           ->where('xk_teacher_id',$id); 
 
       $query =  DB::table('zhuanlans')->select(['id','zl_name as name','zl_teacher_id as tid','ke_type','created_at']) 
           ->where('zl_teacher_id',$id)->union($xk); 
 
       $querySql = $query->toSql(); 
       $result = DB::table(DB::raw("($querySql) as a"))->mergeBindings($query) 
           ->orderBy('created_at','desc')->paginate(10);