Usage of row_number () over (partition by xxx order by xxx) in Oracle

Usage of row_number () over (partition by xxx order by xxx) in Oracle row_number () over (partition by a order by B) in www.2cto.com, the query results are grouped by the field (partition), and then sorted by the B field in the Group. As for asc or desc, you can choose one by yourself, then, a rownumber is returned for each record to mark the order as shown in the preceding table, grouped by deptid, and sorted by salary in descending order in the group, rank is the returned rownumber www.2cto.com. This is grouped by deptid = 10. There are two records in the group, and salary is sorted in descending order. rank is.