SQL query

Nazdar,
ako mam spravit dopyt na tieto tabulky

-----------------
ZAMESTNANCI
-----------------
Column Name DataType Nullable Default Primary Key
ID NUMBER No - 1
MENO VARCHAR2(25) No - -
PRIEZVISKO VARCHAR2(25) No - -

-----------------
ZASIELKA
-----------------
Column Name DataType Nullable Default Primary Key
ID NUMBER No - 1
ID_ZAMESTNANEC NUMBER No - -

tak aby vysledna tabulka vyzerala takto:
MENO PRIEZVISKO POCET_ZASIELOK

skusal som to cez joiny a pouzil som tam group by na ID_ZAMESTNANEC a count na ZASIELKA.ID ale stale mi vypisuje ze podla toho stlpca nemozem robit GROUP BY

Moze mi niekto napisat query ako by to malo vyzerat. Dikes

ok diky pomohlo...
este mi mozes povedat ako zvisim timestamp o jeden mesiac ? lebo ak dam timestamp + 30 tak mi to zvisi o 30 dni ale nebude to dobre ak mesiac bude mat 31 dni
dik

proste chcel by som nieco take aby

select z.meno, z.priezvisko, count(b.id) pocet_zasielok from zamestnanci z left join zasielka b on z.id=b.id_zamestnanec
group by z.id, z.meno, z.priezvisko order by pocet_zasielok desc where b.cas_odoslania > (select systimestamp - "MESIAC" from dual );

ano robim to v oracle,
spravil som to takto:

select z.meno, z.priezvisko, count(b.id) pocet_zasielok
from zamestnanci z
left join zasielka b
on z.id=b.id_zamestnanec
group by z.id, z.meno, z.priezvisko, b.cas_odoslania
order by pocet_zasielok desc
where b.cas_odoslania > (select add_months(systimestamp, -1) from dual);

ale nechapem preco to nefunguje, ked dam osobitne select add_months(systimestamp, -1) from dual tak to vypise vporiadku, ale ked to len spojim s where tak mi vypise
ORA-00933: SQL command not properly ended

no skusam to takto

select z.meno, z.priezvisko, count(b.id) pocet_zasielok
from zamestnanci z
left join zasielka b
on z.id=b.id_zamestnanec
group by z.id, z.meno, z.priezvisko
order by pocet_zasielok desc
where b.cas_odoslania > add_months(systimestamp, -1);

ale stale vypisuje ORA-00933: SQL command not properly ended

velmi pekne dakujem... babral som sa tu s tym cely den... uz to ide