rank()与dense_rank()的分析

1.rank()分析函数

语法:
RANK() OVER([PARTITION BY expr1[,expr2,..,exprn]] ORDER BY expr1[,expr2,..,exprn])

   功能:                                                                                                                                            先将记录按PARTITION分组,组内再以ORDER BY排序,算出当前记录在组内所处的级别(名次). PRATITION条件省略时,表明不分组,或将全录记录作为一组

例子: 有表如下:

SQL> select * from test; NAME       SUBJECT         SCORE ---------- ---------- ---------- aa         chinese            90 aa         art                     88 aa         english            80 bb         chinese            80 bb         art                     92 bb         english            96 cc         chinese            73 cc         art                      78 cc         english            60 已选择9行。

执行语句如下:

SQL> break on name skip 1; SQL> select * from ( select name ,subject,score ,rank() over ( partition by name order by score desc)  score_rank  from  test)  where score_rank<=3; NAME       SUBJECT         SCORE SCORE_RANK ---------- ---------- ---------- ---------- aa         chinese            90          1                  art                88          2            english            80          3 bb         english            96          1                  art                92          2            chinese            80          3 cc            art                78          1            chinese            73          2            english            60          3 已选择9行。

 

SQL> select * from (select name ,subject,score ,rank() over ( partition by subject order by score desc) score_rank from test) where score_rank<=3; NAME       SUBJECT         SCORE SCORE_RANK ---------- ---------- ---------- ---------- bb         art                92          1 aa                            88          2 cc                            78          3 aa         chinese     90          1 bb                            80          2 cc                            73          3 bb         english     96          1 aa                            80          2 cc                            60          3 已选择9行。

2.dense_rank函数

DENSE_RANK分析函数

语法:DENSE_RANK() OVER([PARTITION BY expr1[,expr2,..,exprn]] ORDER BY expr1[,expr2,..,exprn])

 

SQL> insert into test values('dd','chinese',80); 已创建 1 行。 SQL> insert into test values('dd','art',78); 已创建 1 行。 SQL> insert into test values('dd','english',96); 已创建 1 行。 SQL> select * from (select name ,subject,score,dense_rank() over ( partition by subject order by score desc) score_rank from test) where score_rank<=3; NAME       SUBJECT         SCORE SCORE_RANK ---------- ---------- ---------- ---------- dd         art                96          1 bb                            92          2 aa                            88          3 aa         chinese            90          1 bb                            80          2 cc                            73          3 bb         english            96          1 aa                            80          2 cc                            60          3 已选择9行。

SQL>  select * from (select name ,subject,score ,dense_rank() over ( partition by name order by score desc) score_rank from test) where score_rank<=3; NAME       SUBJECT         SCORE SCORE_RANK ---------- ---------- ---------- ---------- aa         chinese            90          1 aa         art                     88          2 aa         english            80          3 bb                                 96          1 bb         art                    92          2 bb         chinese            80          3 cc         art                     78          1 cc         chinese            73          2 cc         english            60          3 dd         art                   96          1 dd                               80          2 dd                               78          3 已选择12行。

SQL> select * from (select name ,subject,score,rank() over ( partition by name order by score desc) score_rank from test) where score_rank<=3; NAME       SUBJECT         SCORE SCORE_RANK ---------- ---------- ---------- ---------- aa         chinese            90          1 aa         art                     88          2 aa         english            80          3 bb                                  96          1 bb         art                      92          2 bb         chinese            80          3 cc         art                      78          1 cc         chinese            73          2 cc         english            60          3 dd         art                96          1 dd                            80          2 dd                            78          3 已选择12行。 SQL> select * from (select name ,subject,score,rank() over ( partition by subject order by score desc) score_rank from test) where score_rank<=3; NAME       SUBJECT         SCORE SCORE_RANK ---------- ---------- ---------- ---------- dd         art                96          1 bb                            92          2 aa                            88          3 aa         chinese      90          1 bb                            80          2 cc                            73          3 bb         english       96          1 aa                            80          2 cc                            60          3 已选择9行。