oracle 里面经常这样用
select col1,col2…, row_number() over (partition by colx order by coly) from table_name;;
这句话的意思是把表中的数值按照colx 分组，每一组内部按照coly排序，同时 row_number()返回排序之后该记录在改组内部的序号。
比如我们知道有emp表如下：
SQL> SELECT * FROM SCOTT.EMP;
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ------------------------------ --------------------------- ---------- ------------------ ---------- ---------- ----------
7369 SMITH CLERK 7902 17-DEC-80 800 20
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7876 ADAMS CLERK 7788 23-MAY-87 1100 20
7900 JAMES CLERK 7698 03-DEC-81 950 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10
用下面的语句显示如下：
SQL> SELECT ENAME,DEPTNO,EMPNO,ROW_NUMBER() OVER(PARTITION BY DEPTNO ORDER BY EMPNO) FROM SCOTT.EMP; ENAME DEPTNO EMPNO ROW_NUMBER()OVER(PARTITIONBYDEPTNOORDERBYEMPNO) ------------------------------ ---------- ---------- ----------------------------------------------- CLARK 10 7782 1 KING 10 7839 2 MILLER 10 7934 3 SMITH 20 7369 1 JONES 20 7566 2 SCOTT 20 7788 3 ADAMS 20 7876 4 FORD 20 7902 5 ALLEN 30 7499 1 WARD 30 7521 2 MARTIN 30 7654 3 BLAKE 30 7698 4 TURNER 30 7844 5 JAMES 30 7900 6
转自：https://www.cnblogs.com/kramer/p/3899855.html