ORACLE OLAP函数语法的总结

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数
最近这个东东用得非凡多，总结了一下 。 语法: FUNCTION_NAME(,,...)
OVER
()
OLAP函数语法四个部分:
1、function本身 用于对窗口中的数据进行操作；
2、partitioning clause 用于将结果集分区；
3、order by clause 用于对分区中的数据进行排序；
4、windowing clause 用于定义function在其上操作的行的集合，即function所影响的范围。 一、order by对窗口的影响
不含order by的：
SQL> select deptno,sal,sum(sal) over()
2 from emp;
不含order by时，默认的窗口是从结果集的第一行直到末尾。
含order by的：
SQL> select deptno,sal,
2 sum(sal) over(order by deptno) as sumsal
3 from emp;
当含有order by时，默认的窗口是从第一行直到当前分组的最后一行。 二、用于排列的函数
SQL> select empno, deptno, sal,
2 rank() over
3 (partition by deptno order by sal desc nulls last) as rank,
4 dense_rank() over
5 (partition by deptno order by sal desc nulls last) as dense_rank,
6 row_number() over
7 (partition by deptno order by sal desc nulls last) as row_number
8 from emp; 三、用于合计的函数
SQL> select deptno,sal,
2 sum(sal) over (partition by deptno) as sumsal,
3 avg(sal) over (partition by deptno) as avgsal,
4 count(*) over (partition by deptno) as count,
5 max(sal) over (partition by deptno) as maxsal
6 from emp; 四、开窗语句 1、rows窗口: "rows 5 preceding" 适用于任何类型而且可以order by多列。 SQL> select deptno,ename,sal,
2 sum(sal) over (order by deptno rows 2 preceding) sumsal
3 from emp; rows 2 preceding:将当前行和它前面的两行划为一个窗口，因此sum函数就作 用在这三行上面
SQL> select deptno,ename,sal,
2 sum(sal) over
3 (partition by deptno order by ename rows 2 preceding) sumsal
4 from emp
5 order by deptno,ename;
加了partiton by分区后之后，rows 2 preceding(窗口)只在当前分区内生效，不会影响分区之外的行。
SQL> select ename,sal,hiredate,
2 first_value(ename)over

3 (order by hiredate asc rows 5 preceding) first_ename,
4 first_value(hiredate) over
5 (order by hiredate asc rows 5 preceding) first_hiredate
6 from emp
7 order by hiredate asc;
order by hiredate asc rows 5 preceding: order by之后，取当前行的前5行 当前行作为窗口(共6行)。
2、"range unbounded preceding" range unbounded preceding会把当前行之前的所有行都包含进来，但当partition by时: SQL> select deptno,ename,sal,
2 sum(sal) over
3 (partition by deptno order by deptno range unbounded preceding) sumsal
4 from emp;
SQL> select deptno,ename,sal,
2 sum(sal) over
3 (order by deptno range unbounded preceding) sumsal
4 from emp;
这SQL句子和下面这SQL是等价的: select deptno,ename,sal,
sum(sal) over (order by deptno) sumsal

转自http://www.mscto.com/Oracle/2009010138636.html