select department_id, job_id, count(*) from hr.employees group by department_id, job_id order by 1;
V(department_id, job_id, pocet) ← department_id, job_id F COUNT employee_id (employees)
1. do zatvorky k V piseme len vtedy ak mame viac stlpcov, alebo aj vtedy ak mame len jeden ?
2. department_id, job_id ktore je pred Fkom, je tam preto lebo je to group podla department_id, job_id ?
3. za Fko davam vsetky "stlpce" ale kedze department_id, job_id je uz red fkom, tak to tam uz dalsi krat nedavam ?
dobre rozumiem ?