数据库第三次作业
在数据库中创建一个表student用于存储学生信息
向student表中添加一条新记录
记录中id字段的值为1name字段的值为"monkey"grade字段的值为98.5
向student表中添加多条新记录
“bob”,95.5
“john”,90.0
“smith”,88.5
向student表中添加一条新记录，部分数据插入
“jone”
更新表，grade 大于90的加0.5
删除成绩为空的记录
mysql> create database stu;
mysql> create table student(
-> id int primary key,
-> name varchar(20) not null,
-> grade float
-> );
mysql> insert into student values(1,'monkey',98.5);
mysql> insert into student values(2,'bob',95.5),(3,'john',90.0),(4,'smith',88.5);
mysql> insert into student(id,name)values(5,'jone');
mysql> update student
-> set grade=grade+0.5
-> where grade>90;
mysql> delete from student
-> where grade is null;
mysql> select * from student;
+----+--------+-------+
| id | name | grade |
+----+--------+-------+
| 1 | monkey | 99 |
| 2 | bob | 96 |
| 3 | john | 90 |
| 4 | smith | 88.5 |
+----+--------+-------+
用户权限部分
创建一个用户test1使他只能本地登录拥有查询student表的权限
查询用户test1的权限
删除用户test1
mysql> create user test1@localhost identified by '20040830Nmx@';
mysql> grant select on student.* to test1@localhost;
mysql> show grants for 'test1'@localhost;
+----------------------------------------------------+
| Grants for test1@localhost |
+----------------------------------------------------+
| GRANT USAGE ON *.* TO `test1`@`localhost` |
| GRANT SELECT ON `student`.* TO `test1`@`localhost` |
+----------------------------------------------------+
mysql> DELETE FROM mysql.user WHERE Host='localhost' AND User='test1';
mysql> FLUSH PRIVILEGES;