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 |
+----+--------+--------+
