sql - oracle window functions -

could me out query:

select sum(summa), name,         to_char(invoice_date, 'yyyy/mm')             on (partiton extract(month i.invoice_date, c.name)  invoice i, customer c  i.customer_id = c.id , months_between(sysdate, invoice_date) = 3 , rownum < 11 group invoice_date, name order sum(summa) desc; 

supposed first ten rows last 3 months, grouped month , ordered sum.

thanks.

first, use proper explicit join syntax. second, need row_number():

select t.* (select sum(summa) sumsumma, name,               to_char(invoice_date, 'yyyy/mm') yyyymm,              row_number() on (partition to_char(invoice_date, 'yyyy/mm')                                 order sum(summa) desc                                ) seqnum       invoice join            customer c             on i.customer_id = c.id       months_between(sysdate, invoice_date) = 3       group invoice_date, name      ) t seqnum <= 10 order sumsumma desc;