宝安22期—秦绍祥-mysql单表查询作业
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);
1，查询1832班的成绩信息
select english,chinese,math from where class=1832;
english chinese math
90 80 77
90 90 90
80 60 88
2，查询1833班，语文成绩大于80小于90的所有成绩信息
select * from GRADE where chinese > 80 and chinese < 90;
ID NAME AGE CLASS CHINESE ENGLISH MATH
4 zhaoliu 17 1833 85 78 85
3，查询学生表中5到10行的数据
select * from GRADE where ID limit 4,6;
ID NAME AGE CLASS CHINESE ENGLISH MATH
5 xiaoqi 17 1832 60 80 88
6 xiaoba 18 1833 70 82 90
4，显示1832班英语成绩为98，数学成绩为77的姓名与学号,
select * from GRADE where class=1832 and english=98 and math=77;
无此人
5，查询出1832班成绩并且按语文成绩排序（降序）
select * from GRADE where class=1832 order by chinese desc;
ID NAME AGE CLASS CHINESE ENGLISH MATH
2 lisi 18 1832 90 90 90
1 zhangsan 18 1832 79 90 77
5 xiaoqi 17 1832 60 80 88
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 * from GRADE where (class=1833 or class=1832) and chinese < 80 and math < 80;
查无此人
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 from GRADE where chinese is null;
查无此人
8，求出班上语文成绩不及格的学生姓名
select name from GRADE WHERE chinese < 60;
查无此人
9，求出每个班的数学平均成绩
select avg(math),class from GRADE group by class;
avg(math) class
85.0000 1832
91.6667 1833
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 sum(chinese),class from GRADE group by class;
sum(chinese) class
230 1832
254 1833
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,age from GRADE where chinese > 70 and english > 70 and math > 70;
name age
zhangsan 18
lisi 18
wangwu 19
zhaoliu 17
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,class from GRADE where english > 70 and (chinese > 60 or math > 60);
name class
zhangsan 1832
lisi 1832
wangwu 1833
zhaoliu 1833
xiaoqi 1832
xiaoba 1833
14、统计每个班的人数
select count(ID),class from GRADE GROUP BY class;
count(ID) class
3 1832
3 1833
15、求每个班数学成绩大于80的人数
SELECT count(*),class from GRADEwhere math > 80 group by class;
count(*) class
2 1832
3 1833
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 max(english),class from GRADE group by class;
max(english) class
90 1832
98 1833
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 (physical int(3),chemical int(3),biological int(3));
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