添加数据库

[root@localhost ~]# mysql -uroot -p   #进入mysql数据表`
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
......  #省略部分内容

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> create database school;       #创建新库‘school
Query OK, 1 row affected (0.00 sec)

mysql> show databases;          #查看所有库
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| school             |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

添加数据表

mysql>use school;
mysql> create table info (id int not null,name char(6),score decimal(5,2),age int(4))；
Query OK, 0 rows affected (0.04 sec)

mysql> desc info;   #查看表结构
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id       | int(11)      | NO   |     | NULL    |       |
| name  | char(6)   | YES  |     | NULL    |       |
| score | decimal(5,2) | YES  |  NULL   |       |
| age   | int(4)        | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+

添加数据表内容
mysql> insert into info (id,name,score,age)values(1,'张三',88,33);
Query OK, 1 row affected (0.01 sec)

mysql> insert into info (id,name,score,age)values(2,'李四',48,31);
Query OK, 1 row affected (0.01 sec)

mysql> insert into info (id,name,score,age)values(3,'王五',68,27);
Query OK, 1 row affected (0.00 sec)

mysql> select * from info;   #查看表内容
+----+--------+-------+------+
| id | name   | score | age  |
+----+--------+-------+------+
|  1 | 张三   | 88.00 |   33 |
|  2 | 李四   | 48.00 |   31 |
|  3 | 王五   | 68.00 |   27 |
+----+--------+-------+------+

添加表列
mysql> alter table info add column score decimal(5,2);
Query OK, 0 rows affected (0.05 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select * from info;   #查看表内容
+----+--------+--------+-------+
| id | name   | hobbly | score |
+----+--------+--------+-------+
|  1 | zl        | 看书   |  NULL |
|  2 | 李四   | 上网   |  NULL |
|  5 | kl        | 游泳   |  NULL |
+----+--------+--------+-------+

更改数据
mysql> update info set score=82 where id=1;  #更改id=1的学生成绩为82分
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from info;  #查看更改效果
+----+--------+-------+------+
| id | name   | score | age  |
+----+--------+-------+------+
|  1 | 张三   | 82.00 |   33 |
|  2 | 李四   | 48.00 |   31 |
|  3 | 王五   | 68.00 |   27 |
+----+--------+-------+------+

删除数据表
mysql> drop table info;
Query OK, 0 rows affected (0.02 sec)
mysql> show tables;     #查看是否删除
Empty set (0.00 sec)     #已经删除（空表）

删除库
mysql> drop database school;
Query OK, 0 rows affected (0.01 sec)

mysql> show databases;     #查看school数据库是否删除
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

删除表列（记录条数）
mysql> delete from info where hobbly=1;
Query OK, 1 row affected (0.01 sec)

mysql> select * from info;
+----+--------+-------+------+--------+
| id | name   | score | age  | hobbly |
+----+--------+-------+------+--------+
|  1 | 张三   | 82.00 |   33 |     3        |
|  2 | 李四   | 48.00 |   31 |     5      |
|  3 | 王五   | 68.00 |   27 |      4    |
|  2 | ff        |  55      | 44  |      2     |
|  3 |ww      | 33       |3 1  |     3      |
+----+--------+-------+------+--------+

删除表列（字段）
mysql> select * from info;  #查看数据表
+----+--------+-------+--------+
| id | name   | score | hobbly |
+----+--------+-------+--------+
|  1 | zl        | 88       | 看书   |
|  2 | 李四    | 68      | 上网   |
|  5 | kl        | 88       | 游泳   |
+----+--------+-------+--------+

mysql> alter table info drop column score;   #用alter删除表列

mysql> select * from info; #再次查看数据表
+----+--------+--------+
| id | name   | hobbly |
+----+--------+--------+
|  1 | zl         | 看书   |
|  2 | 李四    | 上网   |
|  5 | kl         | 游泳   |
+----+--------+--------+