宝安22期周海--数据库单表练习题作业：

八、数据库单表练习题作业：

#创建学生表
CREATE TABLE GRADE(
ID INT PRIMARY KEY AUTO_INCREMENT COMMENT'学号',
NAME VARCHAR(20) COMMENT'姓名',
AGE INT COMMENT'年龄',
CLASS INT COMMENT'班级',
CHINESE INT COMMENT'语文分数',
ENGLISH INT COMMENT'英语分数',
MATH INT COMMENT'数学分数'
)ENGINE=INNODB DEFAULT CHARSET=UTF8 COMMENT'学生表';

#插入表数据
insert into GRADE values
(1,'zhangsan',18,1832,80,90,77),
(2,'lisi',18,1832,90,90,90),
(3,'wangwu',19,1833,99,98,100),
(4,'zhaoliu',17,1833,85,78,85),
(5,'xiaoqi',17,1832,60,80,88),
(6,'xiaoba',18,1833,70,82,90);

select * from GRADE;

DELETE FROM GRADE;

DROP table GRADE;

1，查询1832班的成绩信息

select CLASS,CHINESE,ENGLISH,MATH from GRADE where CLASS ='1832';

2，查询1833班，语文成绩大于80小于90的所有成绩信息

select CLASS,CHINESE from GRADE where CLASS ='1833' and CHINESE between 80 and 90;

3，查询学生表中5到10行的数据

select * from GRADE where ID limit 4,2;

4，显示1832班英语成绩为98，数学成绩为77的姓名与学号,

select CLASS,ENGLISH,MATH,ID from GRADE where CLASS ='1832' and ENGLISH ='98' or MATH ='77';

5，查询出1832班成绩并且按语文成绩排序（降序）

select CLASS,ENGLISH,MATH,CHINESE from GRADE where CLASS ='1832' order by CHINESE desc;

6，查询1833班与1832班，语文成绩与数学成绩都小于80的姓名。

select CLASS,CHINESE,NAME from GRADE where CHINESE <80 and MATH <80;

7，查询出没有参加语文考试的学生姓名和班级名称。

select NAME,CLASS,CHINESE from GRADE where CHINESE is null;

8，求出班上语文成绩不及格的学生姓名

select NAME,CLASS,CHINESE from GRADE where CHINESE <60;

9，求出每个班的数学平均成绩

select CLASS,avg(MATH) from GRADE group by class;

10、求出每个班级语文成绩总分 --涉及到每个的时候都需要分组

select CLASS,sum(CHINESE) from GRADE group by class;

11、将语文成绩不及格的学生语文成绩改为60分

update GRADE set CHINESE =60 where CHINESE <60;

12、三科分数都大于70分的人名和年纪

select NAME,ENGLISH,MATH,CHINESE,AGE from GRADE where ENGLISH >70 and MATH >70 and CHINESE >70;

13、求出英语分数高于70且其它任何一科目大于60分的人和班级

select NAME,ENGLISH,MATH,CHINESE,CLASS from GRADE where ENGLISH >70 and MATH >60 or CHINESE >60;

14、统计每个班的人数

select CLASS,count(ID) from GRADE group by class;

15、求每个班数学成绩大于80的人数

select CLASS,MATH,count(ID) from GRADE group by class having MATH >80;


16、求出每个班英语成绩最高的分数和班级名称 --每个班英语成绩最高

select CLASS, max(ENGLISH) from GRADE group by class;  

17、给GRADE表增加3个字段（数据类型及长度自定义，建议要合理，)

alter table GRADE add(height float(3,2) not null, weight float(3,2) not null, phone int(11) not null);