MySql 创建/删除数据库

C:\Users\Mr.Black>mysql -u root -p
Enter password: ****
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.17 MySQL Community Server (GPL)

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mysql> show databases;
+----------------------+
| Database             |
+----------------------+
| information_schema   |
| a_stock              |
| allstuid             |
| dagang1              |
| dagang2              |
| duxue                |
| mxonline             |
| mysql                |
| performance_schema   |
| rail_freightdb       |
| shijiazhuangdianping |
| studentdb            |
| sys                  |
| test2                |
| xicai                |
+----------------------+
15 rows in set (0.06 sec)

mysql> create database us_pwd;
Query OK, 1 row affected (0.02 sec)

mysql> show databases;
+----------------------+
| Database             |
+----------------------+
| information_schema   |
| a_stock              |
| allstuid             |
| dagang1              |
| dagang2              |
| duxue                |
| mxonline             |
| mysql                |
| performance_schema   |
| rail_freightdb       |
| shijiazhuangdianping |
| studentdb            |
| sys                  |
| test2                |
| us_pwd               |
| xicai                |
+----------------------+
16 rows in set (0.00 sec)

-----------------------------------------------

选择数据库

mysql> use us_pwd;
Database changed

------------------------------------------------

设置使用的字符集

mysql> set names utf8;
Query OK, 0 rows affected (0.00 sec)

-------------------------------------------------

建表

mysql> create table user_pwd( user_id int unsigned primary key not null auto_increment, name varchar(20) not null, password varchar(20) not null);
Query OK, 0 rows affected (0.37 sec)

-----------------------------------------------

读取数据表的信息

mysql> select * from user_pwd;
Empty set (0.00 sec)

-----------------------------------------------

向表中插入数据

mysql> insert into user_pwd (name,password) values ("chen","helloword!");
Query OK, 1 row affected (0.09 sec)

mysql> select * from user_pwd;
+---------+------+------------+
| user_id | name | password   |
+---------+------+------------+
|       1 | chen | helloword! |
+---------+------+------------+
1 row in set (0.00 sec)

mysql> insert into user_pwd (user_id, name,password) values (2,"wang","helloword!");
Query OK, 1 row affected (0.09 sec)

mysql> insert into user_pwd  values (3,"yang","123456");
Query OK, 1 row affected (0.08 sec)

mysql> insert into user_pwd  values ("liu","root123");  # 错误！
ERROR 1136 (21S01): Column count doesn't match value count at row 1
mysql> insert into user_pwd  values (4,"liu","root123");
Query OK, 1 row affected (0.08 sec)

mysql> insert into user_pwd (name,password) values ("alice","p@ssw0rd!");
Query OK, 1 row affected (0.12 sec)

mysql> select * from user_pwd;
+---------+-------+------------+
| user_id | name  | password   |
+---------+-------+------------+
|       1 | chen  | helloword! |
|       2 | wang  | helloword! |
|       3 | yang  | 123456     |
|       4 | liu   | root123    |
|       5 | alice | p@ssw0rd!  |
+---------+-------+------------+
5 rows in set (0.00 sec)

------------------------------------------------

更新数据

mysql> update user_pwd set name="wang2", password="abcd123" where user_id="2";
Query OK, 1 row affected (0.08 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from user_pwd;
+---------+-------+------------+
| user_id | name  | password   |
+---------+-------+------------+
|       1 | chen  | helloword! |
|       2 | wang2 | abcd123    |
|       3 | yang  | 123456     |
|       4 | liu   | root123    |
|       5 | alice | p@ssw0rd!  |
+---------+-------+------------+
5 rows in set (0.00 sec)
-----------------------------------------------

删除行数据

mysql> delete from user_pwd where name="yang" and password="root123";  # 这里and是且，要同时满足两个，而不是把含这俩的都删掉
Query OK, 0 rows affected (0.00 sec)

mysql> delete from user_pwd where name="yang" or password="root123";  #改成or就好了
Query OK, 2 rows affected (0.05 sec)

mysql> select * from user_pwd;
+---------+-------+------------+
| user_id | name  | password   |
+---------+-------+------------+
|       1 | chen  | helloword! |
|       2 | wang2 | abcd123    |
|       5 | alice | p@ssw0rd!  |
+---------+-------+------------+
3 rows in set (0.00 sec)

------------------------------------------------

删除一列

mysql> alter table user_pwd drop column name;
Query OK, 0 rows affected (0.90 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> select * from user_pwd;
+---------+------------+
| user_id | password   |
+---------+------------+
|       1 | helloword! |
|       2 | abcd123    |
|       5 | p@ssw0rd!  |
+---------+------------+
3 rows in set (0.00 sec)

-----------------------------------------------

删除表里的数据

mysql> delete from user_pwd;
Query OK, 3 rows affected (0.05 sec)

mysql> create table user_pwd(user_id int unsigned primary key not null auto_increment,name varchar(20) not null,password varchar(20) not null);
ERROR 1050 (42S01): Table 'user_pwd' already exists  # 可以看到表并没有被删除

mysql> show tables;
+------------------+
| Tables_in_us_pwd |
+------------------+
| user_pwd         |
+------------------+
1 row in set (0.00 sec)

------------------------------------------------

删表

mysql> drop table if exists user_pwd;
Query OK, 0 rows affected (0.20 sec)

mysql> show tables;
Empty set (0.00 sec)

------------------------------------------------

删库

mysql> drop database us_pwd;
Query OK, 1 row affected (0.29 sec)

mysql> show databases;
+----------------------+
| Database             |
+----------------------+
| information_schema   |
| a_stock              |
| allstuid             |
| dagang1              |
| dagang2              |
| duxue                |
| mxonline             |
| mysql                |
| performance_schema   |
| rail_freightdb       |
| shijiazhuangdianping |
| studentdb            |
| sys                  |
| test2                |
| xicai                |
+----------------------+
15 rows in set (0.00 sec)