场景
在查询中,我们会用到将数据分组成几类,然后在每一类中进行排序,给一等级。例如查询一个年各个班级内的排名。
数据
首先准备我们的数据。创建了一张表,利用sequence向里面插入了8条数据。
CREATE TABLE KAKA_STUDENT
(
ST_ID NUMBER(10) PRIMARY KEY,
NAME VARCHAR2(20),
CLASS_NAME VARCHAR2(10),
TOTAL_SCORE NUMBER(10)
);
CREATE SEQUENCE KAKA_STUDENT_SEQ
MINVALUE 1
MAXVALUE 99999999999999
START WITH 1
INCREMENT BY 1
NOCACHE
ORDER;
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'zhangsan', 'C1', 658);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'lisi', 'C1', 587);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'wangwu', 'C2', 418);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'maliu', 'C2', 547);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'zhaoqi', 'C2', 701);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'liba', 'C1', 345);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'huangjiu', 'C1', 608);
INSERT INTO KAKA_STUDENT VALUES(KAKA_STUDENT_SEQ.nextval, 'jiashi', 'C2', 508);
此时我们很容易查出年级内的分数排名。
SELECT s.TOTAL_SCORE, s.NAME,s.CLASS_NAME FROM KAKA_STUDENT s ORDER BY s.total_score DESC;
但是,我们现在想在各个班级内部排名。这个时候就要用我们的ROW_NUMBER()函数了。
语法
ROW_NUMBER() 语法如下
ROW_NUMBER() OVER(PARTITION BY COLUMN1 ORDER BY COLUMN2)
用COLUMN1对数据进行分组,用COLUMN2对数据进行排序。应用
在这里,我们对班级进行分组,对分数进行降序排序。如下:
SELECT s.NAME,s.TOTAL_SCORE,s.CLASS_NAME,ROW_NUMBER() OVER(PARTITION BY CLASS_NAME ORDER BY TOTAL_SCORE DESC) as RANK FROM KAKA_STUDENT s;
结果如下: