add slno category wise in apex

select null sl,EMPNO,
ENAME,
JOB,
MGR,
HIREDATE,
SAL,
COMM,
DEPTNO
  from scott.emp

#myreport {
  counter-reset: serial-number;
}

#myreport td:last-child:before {
  counter-increment: serial-number;
  content: counter(serial-number);
}


#myreport {
  counter-reset: serial-number;
}

#myreport td:first-child:before {
  counter-increment: serial-number;
  content: counter(serial-number);
}