ROW_NUMBER() OVER()
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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 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。
本文出自 “DBA的天空” 博客，请务必保留此出处http://kevinora.blog.51cto.com/9406404/1908883
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