oracle row_number() over(partition by .. order by ..)和rank() over(partition by .. order by ..) 和dense_rank() over(partition by .. order by ..)的相似点与区别

新建一个测试表

create table dim_ia_test2(device_number varchar2(20),desc2 varchar2(20))

插入数据后得到：

一、oracle row_number() over(partition by .. order by ..)

只以电话号码排序，默认升序

select device_number,desc2,row_number() over(order by device_number ) rn from dim_ia_test2;

以电话号码分组，并排序

select device_number,desc2,row_number() over(partition by device_number order by device_number ) rn from dim_ia_test2;

row_number的排序特点为顺序排

二、rank() over(partition by .. order by ..)

select device_number,desc2,rank() over(order by device_number ) rn from dim_ia_test2;

select device_number,desc2,rank() over(partition by device_number  order by device_number ) rn from dim_ia_test2;

三、dense_rank() over(partition by .. order by ..)

select device_number,desc2,dense_rank() over(order by device_number ) rn from dim_ia_test2;

select device_number,desc2,dense_rank() over(partition by device_number order by device_number ) rn from dim_ia_test2;

以上是三个排序的开窗函数，row_number() over(partition by .. order by ..)由于是顺序排序，分组和排序都比较有意义；

rank() over(partition by .. order by ..)排序是跳跃的，排序比较有意义；

和dense_rank() over(partition by .. order by ..)排序是顺序的，排序比较有意义；