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     30

14 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     14

14 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 processed

SQL> 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         5000

14 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。