如何计算Oracle数据库中增加/减少的百分比？

Question

我有一个包含3行值的表:

Row1 : 5
Row2 : 8
Row3 : 9

我希望计算增加或减少的百分比:Row2与Row1,Row3相比Row2所以我会有这个表:计算%的公式是: [Row(n+1) - Row(n)] / Row(2)

     Value   Percentage 
Row1 : 5         -
Row2 : 8        60% (increase compared to Row1) | (8-5)/5
Row3 : 9        12.5%(increase compared to Row2)| (9-8)/8

请建议方式或解决方案.

谢谢大家.

Answer 1

您需要使用Oracle Analytical函数LAG:

您的查询将类似于:

SELECT ((value - lagv)/lagv) * 100
  FROM (
        SELECT value,
               LAG(value) OVER(ORDER BY <ordering_column>) as lagv
          FROM table1
);

为了测试我跑了:

WITH t AS (SELECT 1 as rnum,
                  5 AS value FROM DUAL
           UNION
           SELECT 2 as rnum,
                  8 AS value FROM DUAL
           UNION
           SELECT 3 as rnum,
                  9 AS value FROM DUAL
          ) 
SELECT ((value - lagv)/lagv) * 100 AS Percentage
  FROM (
        SELECT value,
               LAG(value) OVER(ORDER BY rnum) as lagv
          FROM t
);

它返回:

Row  Percentage
  1           
  2          60
  3        12.5

由于你需要为我创建了rnum列的LAG函数指定一个订单,我假设你的表有一些你可以使用的排序列,(否则你怎么知道要比较哪些行？).

希望这可以帮助...

编辑:此链接对于了解Oracle的LEAD和LAG功能非常有用.http://www.oracle-base.com/articles/misc/LagLeadAnalyticFunctions.php