The PARTITION BY ORACLE usage

Oracle's record row_number () OVER and PARTITION BY usage.
Generally so used:
Number row_number () OVER to the line, such as 1,2,3,4
the PARTITION BY field of the packet according to, operations such as class or subclass
sort order by

Therefore, writing of the whole code is:
SELECT ROW_NUMBER () the OVER (the PARTITION BY grouping field 1, field 2 ORDER BY packet sort field 1) from table;