数据库基本操作

我叫张贺，贪财好色。一名合格的LINUX运维工程师，专注于LINUX的学习和研究，曾负责某中型企业的网站运维工作，爱好佛学和跑步。
个人博客：

目录

• 1、数据库的连接方式
• 2、数据库的基本操作
  • 1、查看数据库的版本
  • 2、创建数据库DDL
  • 3、查看所有的数据库
  • 4、 删除数据库和删除数据里面的表
  • 5、 查询某个库的表
• 3、数据库的增删改
  • 1、准备操作环境的数据表
  • 2、insert
  • 3、update
  • 4、delete

笔者微信：zhanghe15069028807

目录

• 1、数据库的连接方式
• 2、数据库的基本操作
  • 1、查看数据库的版本
  • 2、创建数据库DDL
  • 3、查看所有的数据库
  • 4、 删除数据库和删除数据里面的表
  • 5、 查询某个库的表
• 3、数据库的增删改
  • 1、准备操作环境的数据表
  • 2、insert
  • 3、update
  • 4、delete

1、数据库的连接方式

本地连接的时候使用mysql -u root -p可以连接数据库，但这只是本地的连接方式，在工作当中我们连接某一上服务器上的数据库，而不是直接本地进行连接。

-P //指定端口，默认是3306
-h //指定主机IP
-u //指定账户名称
-p //指定用户的密码

[root@mysql01 ~]# mysql -u root -p
Enter password: 

2、数据库的基本操作

1、查看数据库的版本

MariaDB [(none)]> select version();
+----------------+
| version()      |
+----------------+
| 5.5.64-MariaDB |
+----------------+
1 row in set (0.00 sec)

2、创建数据库DDL

MariaDB [(none)]> create database bgx_edu;
Query OK, 1 row affected (0.00 sec)

注意

数据库名称严格区分⼤⼩写
数据库名称必须是唯⼀
数据库名称不允许使⽤数字
数据库名称不能使⽤关键字命名 create select

3、查看所有的数据库

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| bgx_edu            |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)
//执行命令不区分大小写
MariaDB [(none)]> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| bgx_edu            |
| mysql              |
| performance_schema |
| test               |
+--------------------+
5 rows in set (0.00 sec)

4、 删除数据库和删除数据里面的表

//删除bgx_edu数据库
MariaDB [(none)]> drop database bgx_edu;
//删除bgx_edu数据库里面的t1表
MariaDB [(none)]> drop database bgx_edu.t1;

5、 查询某个库的表

//进入某个数据库
MariaDB [(none)]> use bgx_edu;
Database changed
//列出当前库里面的表；
MariaDB [bgx_edu]> show tables;
Empty set (0.00 sec)
//查询表结构
MariaDB [mysql]> desc user;
+------------------------+-----------------------------------+------+-----+---------+-------+
| Field                  | Type                              | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+---------+-------+
| Host                   | char(60)                          | NO   | PRI |         |       |
| User                   | char(16)                          | NO   | PRI |         |       |
//查看创建某张表用的语句
MariaDB [mysql]> show create table mysql.slow_logG
*************************** 1. row ***************************
       Table: slow_log
Create Table: CREATE TABLE `slow_log` (
  `start_time` timestamp(6) NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `user_host` mediumtext NOT NULL,
  `query_time` time(6) NOT NULL,
  `lock_time` time(6) NOT NULL,
  `rows_sent` int(11) NOT NULL,
  `rows_examined` int(11) NOT NULL,
  `db` varchar(512) NOT NULL,
  `last_insert_id` int(11) NOT NULL,
  `insert_id` int(11) NOT NULL,
  `server_id` int(10) unsigned NOT NULL,
  `sql_text` mediumtext NOT NULL
) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='Slow log'
1 row in set (0.00 sec)

3、数据库的增删改

在MYSQL管理软件中，可以通过SQL语句中的DML（数据操纵语言）来实现数据的操作，主要用到下面三个指令：

INSERT 数据增加
UPDATE 数据更改
DELETE 数据删除
SELECT 数据查询

1、准备操作环境的数据表

//创建后面要用到的数据库和表
MariaDB [(none)]> create database bgx;
MariaDB [(none)]> use bgx;
MariaDB [bgx]> create table t1
    -> (id int,
    -> name varchar(10),
    -> sex enum('man','gril'),
    -> age int);
//查看表结构
MariaDB [bgx]> desc t1;
+-------+--------------------+------+-----+---------+-------+
| Field | Type               | Null | Key | Default | Extra |
+-------+--------------------+------+-----+---------+-------+
| id    | int(11)            | YES  |     | NULL    |       |
| name  | varchar(10)        | YES  |     | NULL    |       |
| sex   | enum('man','gril') | YES  |     | NULL    |       |
| age   | int(11)            | YES  |     | NULL    |       |
+-------+--------------------+------+-----+---------+-------+

2、insert

insert完整插入语法1：insert into table-name（field1,field2,field3,field4) values (values1，values2，values3，values4)；

MariaDB [bgx]> insert into t1 (id,name,sex,age) values ("1","zhanghe","man","22");
MariaDB [bgx]> select * from t1;
+------+---------+------+------+
| id   | name    | sex  | age  |
+------+---------+------+------+
|    1 | zhanghe | man  |   22 |
+------+---------+------+------+

insert完整插入语法2（推荐）：insert table-name values (values1，values2，values3，values4)；

MariaDB [bgx]> insert t1 values ("2","zhangjia","gril","13");
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhanghe  | man  |   22 |
|    2 | zhangjia | gril |   13 |
+------+----------+------+------+

insert指定字段插入语法：insert table-name（field1,field2) values (values1，values2)；

MariaDB [bgx]> insert t1 (id,name) values ("3","zhangwei");
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhanghe  | man  |   22 |
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
+------+----------+------+------+

//insert插入多条数据
MariaDB [bgx]> insert t1 (id,name) values
    -> ("4","zhangsan"),
    -> ("5","lisi");
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhanghe  | man  |   22 |
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
|    4 | zhangsan | NULL | NULL |
|    5 | lisi     | NULL | NULL |
+------+----------+------+------+

3、update

更改某个字段的套路:
先用DESC查看一下字段的名字
然后再用SELECT查看表中的内容
再然后才用UPDATE更改，注意用WHERE精神修改
最的用FLUSH进行刷新

//更改表中的某一个字段的值
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhanghe  | man  |   22 |
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
|    4 | zhangsan | NULL | NULL |
|    5 | lisi     | NULL | NULL |
+------+----------+------+------+
MariaDB [bgx]> update t1 set age=22 where name="zhanghe";
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhanghe  | man  |   22 |
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
|    4 | zhangsan | NULL | NULL |
|    5 | lisi     | NULL | NULL |
+------+----------+------+------+

//用update修改root的密码
///先找出要修改的什么字段
MariaDB [mysql]> desc mysql.user;
+------------------------+-----------------------------------+------+-----+---------+-------+
| Field                  | Type                              | Null | Key | Default | Extra |
+------------------------+-----------------------------------+------+-----+---------+-------+
| Host                   | char(60)                          | NO   | PRI |         |       |
| User                   | char(16)                          | NO   | PRI |         |       |
| Password               | char(41)                          | NO   |     |         |       |
///然后将要修改的字段列出来
MariaDB [mysql]> select host,user,password from user;
+-----------+------+----------+
| host      | user | password |
+-----------+------+----------+
| localhost | root |          |
| mysql01   | root |          |
| 127.0.0.1 | root |          |
| ::1       | root |          |
| localhost |      |          |
| mysql01   |      |          |
+-----------+------+----------+
///用update进行修改密码
MariaDB [mysql]> update mysql.user set password=password("cba-123") where host='localhost' and user='root';
MariaDB [mysql]> select host,user,password from user;
+-----------+------+-------------------------------------------+
| host      | user | password                                  |
+-----------+------+-------------------------------------------+
| localhost | root | *D1BE934B99C7CFFE2843BDE71DB34BBB0894B2DD |
| mysql01   | root |                                           |
| 127.0.0.1 | root |                                           |
| ::1       | root |                                           |
| localhost |      |                                           |
| mysql01   |      |                                       
///最后再刷新一下
MariaDB [(none)]> flush privileges;

4、delete

语法: DELETE FROM 表名 WHERE CONITION

MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    1 | zhanghe  | man  |   22 |
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
|    4 | zhangsan | NULL | NULL |
|    5 | lisi     | NULL | NULL |
+------+----------+------+------+
MariaDB [bgx]> delete from t1 where name="zhanghe";
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
|    4 | zhangsan | NULL | NULL |
|    5 | lisi     | NULL | NULL |
+------+----------+------+------+
//清空表数据
MariaDB [bgx]> select * from t1;
+------+----------+------+------+
| id   | name     | sex  | age  |
+------+----------+------+------+
|    2 | zhangjia | gril |   13 |
|    3 | zhangwei | NULL | NULL |
|    4 | zhangsan | NULL | NULL |
|    5 | lisi     | NULL | NULL |
+------+----------+------+------+
MariaDB [bgx]> truncate t1;
MariaDB [bgx]> select * from t1;
Empty set (0.00 sec)