SQL: ordinal number of row in group

select l.jobid, l.cityid, (select count(*) + 1 from tbljob_city where jobid = l.jobid and cityid < l.cityid) as ordinal_number from tbljob_city l where l.jobid = 7 or l.jobid = 30 order by l.jobid, l.cityid;
+-------+--------+----------------+
| jobid | cityid | ordinal_number |
+-------+--------+----------------+
|     7 |     24 |              1 |
|     7 |     29 |              2 |
|    30 |     24 |              1 |
|    30 |     29 |              2 |
+-------+--------+----------------+