ROW_NUMBER() OVER()

ROW_NUMBER()OVER() 是Oracle SQL分析函数，主要是用来对要查询的数据分组排序使用。
使用方法
ROW_NUMBER()OVER(PARTITION BY col1 ORDER BY col2）
对列col1分组，col2排序操作。
例子：

SQL> SELECT   2   ROW_NUMBER()OVER(PARTITION BY deptno ORDER BY sal, empno) AS rn,  3   empno, ename, sal, deptno  4  FROM emp;    RN  EMPNO ENAME     SAL DEPTNO---------- ---------- ---------- ---------- ----------     1   7934 MILLER           1300     10     2   7782 CLARK        2450     10     3   7839 KING         5000     10     1   7369 SMITH     800     20     2   7876 ADAMS        1100     20     3   7566 JONES        2975     20     4   7788 SCOTT        3000     20     5   7902 FORD         3000     20     1   7900 JAMES     950     30     2   7521 WARD         1250     30     3   7654 MARTIN           1250     30    RN  EMPNO ENAME     SAL DEPTNO---------- ---------- ---------- ---------- ----------     4   7844 TURNER           1500     30     5   7499 ALLEN        1600     30     6   7698 BLAKE        2850     3014 rows selected.

同时也可以单独使用其来对结果进行排序
可以和order by 对比一下：

SQL> SELECT empno, ename, sal,  2    ROW_NUMBER()OVER(ORDER BY sal, empno) AS rn  3  FROM emp;     EMPNO ENAME       SAL        RN---------- ---------- ---------- ----------      7369 SMITH          800         1      7900 JAMES          950         2      7876 ADAMS         1100      3      7521 WARD             1250      4      7654 MARTIN        1250      5      7934 MILLER        1300      6      7844 TURNER        1500      7      7499 ALLEN         1600      8      7782 CLARK         2450      9      7698 BLAKE         2850     10      7566 JONES         2975     11     EMPNO ENAME       SAL        RN---------- ---------- ---------- ----------      7788 SCOTT         3000     12      7902 FORD             3000     13      7839 KING             5000     1414 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 3145491563---------------------------------------------------------------------------| Id  | Operation      | Name | Rows  | Bytes | Cost (%CPU)| Time    |---------------------------------------------------------------------------|   0 | SELECT STATEMENT   |         |    14 |   462 |      4  (25)| 00:00:01 ||   1 |  WINDOW SORT    |       |    14 |   462 |      4  (25)| 00:00:01 ||   2 |   TABLE ACCESS FULL| EMP  |    14 |   462 |    3   (0)| 00:00:01 |---------------------------------------------------------------------------Note-----   - dynamic sampling used for this statement (level=2)Statistics----------------------------------------------------------          5  recursive calls          0  db block gets         16  consistent gets          1  physical reads          0  redo size       1049  bytes sent via SQL*Net to client        523  bytes received via SQL*Net from client          2  SQL*Net roundtrips to/from client          1  sorts (memory)          0  sorts (disk)         14  rows processedSQL> SELECT empno, ename, sal  2  FROM emp  3  ORDER BY sal, empno;     EMPNO ENAME       SAL---------- ---------- ----------      7369 SMITH          800      7900 JAMES          950      7876 ADAMS         1100      7521 WARD             1250      7654 MARTIN        1250      7934 MILLER        1300      7844 TURNER        1500      7499 ALLEN         1600      7782 CLARK         2450      7698 BLAKE         2850      7566 JONES         2975     EMPNO ENAME       SAL---------- ---------- ----------      7788 SCOTT         3000      7902 FORD             3000      7839 KING             500014 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 150391907---------------------------------------------------------------------------| Id  | Operation      | Name | Rows  | Bytes | Cost (%CPU)| Time    |---------------------------------------------------------------------------|   0 | SELECT STATEMENT   |         |    14 |   462 |      4  (25)| 00:00:01 ||   1 |  SORT ORDER BY     |       |    14 |   462 |      4  (25)| 00:00:01 ||   2 |   TABLE ACCESS FULL| EMP  |    14 |   462 |    3   (0)| 00:00:01 |---------------------------------------------------------------------------Note-----   - dynamic sampling used for this statement (level=2)Statistics----------------------------------------------------------          4  recursive calls          0  db block gets         16  consistent gets          1  physical reads          0  redo size        943  bytes sent via SQL*Net to client        523  bytes received via SQL*Net from client          2  SQL*Net roundtrips to/from client          1  sorts (memory)          0  sorts (disk)         14  rows processed

对比ORDER BY 子句，排序结果一样，使用ROW_NUMBER()OVER()函数可生产RN列，便于在某些列表程序选择行数。