Oracle高级函数使用的浅显介绍

-- 分组统计时不受限制的统计所有记录
SELECT   deptno, COUNT (1),
SUM (COUNT (1)) OVER(ORDER BY deptno DESC ROWS
BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS aaa,
SUM(COUNT(1)) OVER() AS aaaa
FROM emp GROUP BY deptno;

-- 三个排序方式不同的排序函数
SELECT empno,sal,RANK() OVER(ORDER BY sal DESC) AS aa,
DENSE_RANK() OVER(ORDER BY sal DESC) AS aaa,
ROW_NUMBER() OVER(ORDER BY sal DESC) AS aaaa
FROM EMP;

-- 排序，分别获取第一个和最后一个
SELECT MIN(empno) KEEP(DENSE_RANK FIRST ORDER BY sal DESC) AS aa,
MIN(empno) KEEP(DENSE_RANK LAST ORDER BY sal DESC) AS aaa
FROM emp;

-- 百分比
SELECT   months,
ROUND (RATIO_TO_REPORT (SUM (tot_sales)) OVER (), 2) AS aaa
FROM orders
GROUP BY months

-- 平均分成五个级别
SELECT empno,NTILE(5) OVER(ORDER BY sal DESC) AS aa FROM emp;

-- 取当前行的后指定行的汇总数据
SELECT months,SUM(tot_sales) monthly_sales,
LAG(SUM(tot_sales),2) OVER(ORDER BY months) prev_month_sales
FROM orders
GROUP BY months;