3.13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);
1，查询1832班的成绩信息
select 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 CHINESE,ENGLISH,MATH from GRADE where (class=1833) AND CHINESE>80 AND CHINESE<90;
3，查询学生表中5到10行的数据
SELECT*FROM GRADE LIMIT 4,6;
4，显示1832班英语成绩为98，数学成绩为77的姓名与学号,
SELECT NAME,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*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 NAME FROM GRADE WHERE(CLASS=1833 AND CHINESE<80 AND MATH<80) OR (CLASS=1832 AND 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 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 FROM GRADE WHERE CHINESE<60;
9，求出每个班的数学平均成绩
SELECT AVG(MATH) FROM GRADE WHERE CLASS=1833;
SELECT AVG(MATH) FROM GRADE WHERE CLASS=1832;
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 AVG(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,AGE FROM GRADE WHERE CHINESE>70 AND MATH>70 AND ENGLISH>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,CLASS FROM GRADE WHERE ENGLISH>70 AND (MATH>70 OR CHINESE>70);
14、统计每个班的人数
SELECT COUNT(*) FROM GRADE WHERE CLASS=1833;
SELECT COUNT(*) FROM GRADE WHERE CLASS=1832;
15、求每个班数学成绩大于80的人数
SELECT COUNT(*) FROM GRADE WHERE 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 MAX(ENGLISH) FROM GRADE WHERE CLASS=1833;
SELECT MAX(ENGLISH) FROM GRADE WHERE CLASS=1832;
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(4,2),WEIGHT FLOAT(5,2),time date);
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