sum over 分析函数用法

 

sum over 分析函数用法

首先表如下：   A B C D 1 A                                1                                2                                3                                2 B                                1                                3                                4                                3 C                                2                                4                                5                                4 D                                2                                5                                6                                5 E                                3                                6                                7                                over的用法： over主要是和汇总函数配合产生出额外的列                  例如：SELECT T.A ,T.B,T.C,SUM(C) OVER(PARTITION BY B ORDER BY A) SUM1 FROM TEST T 这句的意思是：从TEST表中查出A,B,C三列再加上SUM1这一列，SUM1是以A列排序，以B列分组，从C列 连续加总得到的数放在对应的SUM1列里面，例如：SUM1=5表示B＝1的并且在第二行以前的和即2+3＝5   A B C SUM1 1 A                                1                                2                                2 2 B                                1                                3                                5 3 C                                2                                4                                4 4 D                                2                                5                                9 5 E                                3                                6                                6 SUM(C)是汇总函数，也可以用其它的如：AVG(),COUNT()等 PARTITION 是指定按哪行分组 ORDER 指定排序，用在OVER函数里说明是连续的进行汇总。如果不加的话结果如下： SELECT T.A ,T.B,T.C,SUM(C) OVER(PARTITION BY B ORDER BY T.A) SUM1 ,SUM(C) OVER(PARTITION BY B ) SUM2 FROM TEST T   A B C SUM1 SUM2 1 A                                1                                2                                2 5 2 B                                1                                3                                5 5 3 C                                2                                4                                4 9 4 D                                2                                5                                9 9 5 E                                3                                6                                6 6 注意SUM1和SUM2的区别。 注： 1、如果先partition by X后order by Y则在分组的前提下，同组中X字段值一样的记录再按Y字段排序，然后sum(a)over()的作用就是按a字段累加----分组连续求和 2、若没有order by Y则sum(a) over()的执行是把分组后同组的记录一起处理，当作一条记录来看待----分组求总和 3、若两者皆没有，即sum(a)over(),over后的括号中为空，则sum(a)over()字段的值为a列所有值的和，每一条记录的sum(a)over()都一样----求总和

转自：http://ljx198308.blog.163.com/blog/static/176274246201011935246547/?fromdm&fromSearch&isFromSearchEngine=yes