ORACLE----多表查询语句练习

--建表CLASSINFO；
CREATE TABLE CLASSINFO (
  CLASSID NUMBER(2) PRIMARY KEY,
  CLASSNAME VARCHAR(10) NOT NULL);

--建表STUDENTINFO；
CREATE TABLE STUDENTINFO (
  STUDENTID NUMBER(2) PRIMARY KEY ,
  STUDENTNAME CHAR(10) NOT NULL,
  STUDENTSEX CHAR(2) CHECK(STUDENTSEX=‘男‘ OR STUDENTSEX=‘女‘),
  STUDENTAGE NUMBER(2) NOT NULL,
  STUDENTTEL NUMBER(11) UNIQUE,
  STUDENTADDRESS VARCHAR(20) DEFAULT ‘上海‘,
  classid number(2) REFERENCES classinfo(classid));

--表CLASSINFO；
INSERT INTO CLASSINFO (CLASSID,CLASSNAME) VALUES( 1,‘六班‘);
INSERT INTO CLASSINFO (CLASSID,CLASSNAME) VALUES( 2,‘七班‘);

INSERT INTO STUDENTINFO  VALUES (1,‘Timmy‘,‘男‘,20,‘13285601693‘,‘suzhou‘,1 ); 
ALTER TABLE STUDENTINFO MODIFY  (STUDENTNAME  CHAR(10) );--这里是来修改STUDETNAME字段的数据类型的长度。
INSERT INTO STUDENTINFO  VALUES (2,‘Lizmer‘,‘男‘,25,‘18056947153‘,‘anhui‘,1 ); 
INSERT INTO STUDENTINFO  VALUES (3,‘Gray‘,‘男‘,30,‘18056996153‘,‘hubei‘,2 ); 
INSERT INTO STUDENTINFO  VALUES (4,‘Roger‘,‘男‘,31,‘18056886153‘,‘henan‘,2 );

ALTER TABLE CLASSINFO ADD (Teacher char(20));
ALTER TABLE CLASSINFO ADD (Leader char(20));
ALTER TABLE STUDENTINFO ADD (SCORE NUMBER(20));
ALTER TABLE STUDENTINFO ADD (Teacher char(20));

UPDATE CLASSINFO SET Teacher=‘刘A‘ where  CLASSID=‘2‘;
UPDATE CLASSINFO SET Leader=‘陈B‘ where  CLASSID=‘2‘;
UPDATE STUDENTINFO SET Teacher=‘张I‘ where  STUDENTID=‘4‘;
UPDATE STUDENTINFO SET Leader=‘汤J‘ where  STUDENTID=‘4‘;
UPDATE STUDENTINFO SET SCORE=‘100‘ where  STUDENTID=‘5‘;

##我们通常将group by叫做分组，而partition by称作分区，分组返回通常是一行，partition by返回的是多行。
SELECT STUDENTINFO.*,DENSE_RANK() OVER(ORDER BY STUDENTINFO.SCORE DESC ) AS RANKS 
  FROM STUDENTINFO;
SELECT STUDENTINFO.*,RANK() OVER(ORDER BY STUDENTINFO.SCORE DESC ) AS RANKS 
  FROM STUDENTINFO;
SELECT RANK() OVER(PARTITION BY STUDENTNAME ORDER BY STUDENTINFO.SCORE DESC ) AS RANKS 
  FROM STUDENTINFO;--这里解释一下，假如Timmy有两次得分记录，那么上述语句就是对Timmy的得分排序。