how properly use inner join in sql

Question

I have two tables:

depart

debt city
43   odesa
23   kiev
79   kiev
78   donezk

and

empl

ide   fn    ln      debt
3421  jed   trt       43
 354  jed   res       43
  43  ged   hjkhg     79
  73  ghghg gfgf      79
 456  jkl   gdfg      78
 532  kkhg  vjv       23
  45  ki    vt        79
 243  ki    vt        78

I need choose rows number of employees (fn) of each department (debt) and sort them by city. I wrote this code:

select empl.DEBT, count (*) as emp_num 
from depart 
inner join empl on empl.DEBT = depart.DEBT
group by empl.DEBT
order by depart.CITY;

But this code doesn't work. What do I do wrong?

I use Oracle db, execute script in Toad.

Error message is

The following error has occurred: ORA-00900: invalid SQL statement

Answer 1

select empl.DEBT, count (*) as emp_num 
from depart 
inner join empl on empl.DEBT = depart.DEBT
group by depart.CITY,empl.DEBT
order by depart.CITY;

Answer 2

For you to order by city, then you also need to group by city:

select empl.DEBT, count (*) as emp_num 
from depart 
inner join empl 
on empl.DEBT = depart.DEBT
group by empl.DEBT, depart.CITY
order by depart.CITY;