2021.2.2—作业：数据库单表

1、查询1832班的成绩信息
答：select chinese english math from grade where class=1832;
2、查询1833班，语文成绩大于80小于90的成绩信息
答：select chinese 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
答：select * from grade where id 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
答：select id,name from grade where class=1832 and english=98 and math=77;
5、查询出1832班成绩并且按语文成绩排序（降序）
答：select chinese english math 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
答：select name from grade where chinese<80 and math<80 order by class,id having class=1833 or class=1832;
7、查询出没有参加语文考试的学生姓名和班级名称
答：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
答：select name from grade where chinese<60;
9、求出每个班的数学平均成绩
答：select class,avg(math) as '数学平均成绩' from grade group by class;
10、求出每个班级语文成绩总分
答：select class,sum(chinese) as '语文成绩总分' from grade group by class;
11、将语文成绩不及格的学生成绩改为60分
答：update grade set chinese=60 where chinese<60;
12、三科分数都大于70分的人名和年纪
答：select name,age from grade where chinese>70 and english>70 and math>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
答：select name,class from grade where chinese>60 or math>60 group by english,id having english>70;
14、统计每个班的人数
答：select class,count(id) as '人数' from grade group by class;
15、求每个班数学成绩大于80的人数
答：select class,count(id) as '数学成绩大于80的人数' from grade where math>80 group by class;
16、求出每个班英语成绩最高的那个人的姓名和班级名称
答：select name,class from grade group by class having max(english);
17、给student表增加3个字段
答：alter table student add(Physics int(11),Chemistry int(11),Biology int(11));
18、创建一个”dcs”远程用户授予该用户只有查询的权限
答：insert into user(host,user,password,select_priv) values('%','dcs',password('123456'),'Y');