这个函数在oracle帮助文档的位置：SQL Reference里面，很好找的。
除报告详细数据外，许多报告中还包括每行总数的百分比。例如，每名客户的订单相对于总订单的百分比，或每位销售代表的销售额相对于总销售额的百分比。
传统上，Oracle计算百分比的方法是在总计报告的子查询中使用SUM函数总计报告，然后把那个结果放到细节表中相除来计算百分比。你还可以用一个子查询作为SELECT语句表达式：
RATIO_TO_REPORT解析函数使得这种类型的查询更容易编码。Oracle 8i中引入了这个函数，它的格式如下：
RATIO_TO_REPORT (expr) OVER (query_partition_clause)
这个上面的语法我就不多说了，直接看演示的例子吧。
- [root@suys1 ~]# su - oracle
- [oracle@suys1 ~]$ sqlplus / as sysdba
- SQL*Plus: Release 11.2.0.4.0 Production on Fri Jun 6 09:00:03 2014
- Copyright (c) 1982, 2013, Oracle. All rights reserved.
- Connected to an idle instance.
- SQL> startup
- ORACLE instance started.
- Total System Global Area 1653518336 bytes
- Fixed Size 2253784 bytes
- Variable Size 1040190504 bytes
- Database Buffers 603979776 bytes
- Redo Buffers 7094272 bytes
- Database mounted.
- Database opened.
- SQL> conn sec/sec
- Connected.
- SQL>
- SQL> desc emp;
- ERROR:
- ORA-04043: object emp does not exist
- SQL>
- SQL> conn / as sysdba
- Connected.
- SQL> create table sec.emp as select * from scott.emp;--从scott里面造测试数据
- Table created.
- SQL>
- SQL> conn sec/sec
- Connected.
- SQL> select * from emp order by DEPTNO; --检查下造好的数据
- EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
- ---------- ---------- --------- ---------- --------- ---------- ---------- ----------
- 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
- 7839 KING PRESIDENT 17-NOV-81 5000 10
- 7934 MILLER CLERK 7782 23-JAN-82 1300 10
- 7566 JONES MANAGER 7839 02-APR-81 2975 20
- 7902 FORD ANALYST 7566 03-DEC-81 3000 20
- 7876 ADAMS CLERK 7788 23-MAY-87 1100 20
- 7369 SMITH CLERK 7902 17-DEC-80 800 20
- 7788 SCOTT ANALYST 7566 19-APR-87 3000 20
- 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
- 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
- 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
- EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
- ---------- ---------- --------- ---------- --------- ---------- ---------- ----------
- 7900 JAMES CLERK 7698 03-DEC-81 950 30
- 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
- 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
- 14 rows selected.
- SQL> select DEPTNO,sum(sal) from emp group by DEPTNO; --看好这些数，一些说明用
- DEPTNO SUM(SAL)
- ---------- ----------
- 30 9400
- 20 10875
- 10 8750
- SQL> select DEPTNO,sum(sal) from emp group by rollup(DEPTNO);
- DEPTNO SUM(SAL)
- ---------- ----------
- 10 8750
- 20 10875
- 30 9400
- 29025
- SQL>
- SQL> SELECT
- 2 empno,ename,ename,hiredate,sal,deptno,
- 3 ratio_to_report(sal) over () as pct1l,
- 4 ratio_to_report(sal) over (partition by deptno) as pct2
- 5 FROM emp;
- EMPNO ENAME ENAME HIREDATE SAL DEPTNO PCT1L PCT2
- ---------- ---------- ---------- --------- ---------- ---------- ---------- ----------
- 7782 CLARK CLARK 09-JUN-81 2450 10 .084409991 .28
- 7839 KING KING 17-NOV-81 5000 10 .172265289 .571428571
- 7934 MILLER MILLER 23-JAN-82 1300 10 .044788975 .148571429
- 7566 JONES JONES 02-APR-81 2975 20 .102497847 .273563218
- 7902 FORD FORD 03-DEC-81 3000 20 .103359173 .275862069
- 7876 ADAMS ADAMS 23-MAY-87 1100 20 .037898363 .101149425
- 7369 SMITH SMITH 17-DEC-80 800 20 .027562446 .073563218
- 7788 SCOTT SCOTT 19-APR-87 3000 20 .103359173 .275862069
- 7521 WARD WARD 22-FEB-81 1250 30 .043066322 .132978723
- 7844 TURNER TURNER 08-SEP-81 1500 30 .051679587 .159574468
- 7499 ALLEN ALLEN 20-FEB-81 1600 30 .055124892 .170212766
- EMPNO ENAME ENAME HIREDATE SAL DEPTNO PCT1L PCT2
- ---------- ---------- ---------- --------- ---------- ---------- ---------- ----------
- 7900 JAMES JAMES 03-DEC-81 950 30 .032730405 .10106383
- 7698 BLAKE BLAKE 01-MAY-81 2850 30 .098191214 .303191489
- 7654 MARTIN MARTIN 28-SEP-81 1250 30 .043066322 .132978723
- 14 rows selected.
- SQL>
- SQL> SELECT
- 2 empno,ename,ename,hiredate,sal,deptno,
- 3 ratio_to_report(sal) over (partition by deptno order by sal ) as pct2
- 4 FROM emp;
- ratio_to_report(sal) over (partition by deptno order by sal ) as pct2
- *
- ERROR at line 3:
- ORA-30487: ORDER BY not allowed here
从上面的例子，大家可以看出这个函数的用法了。
结果里面的
PCT1L是每个SAL占所有记录的SAL的百分比。比如EMPNO=7782的这行，2450/29025=.084409991
PCT2是每个SAL占自己所在部门的百分比，还拿EMPNO=7782的这行， 2450/8750=0.28
还有ratio_to_report是不支持order by的。