标签：mysqld connect esc int ase for des admin null
MySQL是一个关系型数据库管理系统，由MySQL AB 公司开发，目前属于 Oracle 。MySQL 是最流行的关系型数据库管理系统之一。关系数据库将数据保存在不同的表中，而不是将所有数据放在一个大仓库内，这样就增加了速度并提高了灵活性。MySQL所使用的 SQL 语言是用于访问数据库的最常用标准化语言。拥有体积小、速度快、总体成本低，尤其是开放源码这一特点。
[root@centos6 ~]# service mysqld start
Starting mysqld: [ OK ]
[root@centos6 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.1.73 Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
mysql>
[root@centos6 ~]# mysqladmin -uroot password ‘centos‘
[root@centos6 ~]# mysql -uroot -pcentos
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 5.1.73 Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement.
mysql>
MySQL 安装完成后，它的数据库文件、配置文件和命令文件分别在不同的目录，了解这些目录非常重要，尤其对于Linux的初学者，因为 Linux本身的目录结构就比较复杂，如果搞不清楚MySQL的安装目录那就无从谈起深入学习。
下面就介绍一下这几个目录。
1、 数据库目录
/var/lib/mysql/
2、配置文件
/usr/share /mysql（mysql.server命令及配置文件）
3、相关命令
/usr/bin(mysqladmin mysqldump等命令)
4、启动脚本
/etc/rc.d/init.d/（启动脚本文件mysql的目录）
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hellodb |
| mysql |
| test |
+--------------------+
4 rows in set (0.01 sec)
Mysql刚安装完有两个数据库：mysql和test。mysql库非常重要， 它里面有MySQL的系统信息，我们改密码和新增用户，实际上就是用这个库中的相关表进行操作。
2.显示数据库中的表
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| hellodb |
| mysql |
| test |
+--------------------+
4 rows in set (0.01 sec)
mysql> use hellodb;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show tables;
+-------------------+
| Tables_in_hellodb |
+-------------------+
| classes |
| coc |
| courses |
| scores |
| students |
| teachers |
| toc |
+-------------------+
7 rows in set (0.00 sec)
3.显示数据表的字段结构
mysql> describe classes;
+----------+----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+----------------------+------+-----+---------+----------------+
| ClassID | tinyint(3) unsigned | NO | PRI | NULL | auto_increment |
| Class | varchar(100) | YES | | NULL | |
| NumOfStu | smallint(5) unsigned | YES | | NULL | |
+----------+----------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
也可以使用两一条命令，显示比这个更详细，而且可以把建表语句全部列出来:
mysql> show create table classes\G‘
*************************** 1. row ***************************
Table: classes
Create Table: CREATE TABLE `classes` (
`ClassID` tinyint(3) unsigned NOT NULL AUTO_INCREMENT,
`Class` varchar(100) DEFAULT NULL,
`NumOfStu` smallint(5) unsigned DEFAULT NULL,
PRIMARY KEY (`ClassID`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
4.显示某个表中的记录
mysql> select * from classes;
+---------+----------------+----------+
| ClassID | Class | NumOfStu |
+---------+----------------+----------+
| 1 | Shaolin Pai | 10 |
| 2 | Emei Pai | 7 |
| 3 | QingCheng Pai | 11 |
| 4 | Wudang Pai | 12 |
| 5 | Riyue Shenjiao | 31 |
| 6 | Lianshan Pai | 27 |
| 7 | Ming Jiao | 27 |
| 8 | Xiaoyao Pai | 15 |
+---------+----------------+----------+
8 rows in set (0.01 sec)
5.查询当前是哪个用户
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
6.创建一个新的数据库
mysql> create database hahaha;
Query OK, 1 row affected (0.00 sec)
7.创建一个新表
mysql> use hahaha;
Database changed
mysql> create table t1 (`id` int(4), `name` char(40));
Query OK, 0 rows affected (0.04 sec)
字段名需要用引号括起来
8.查询语句
mysql> select count(*) from students;
+----------+
| count(*) |
+----------+
| 25 |
+----------+
1 row in set (0.00 sec)
students表示mysql库的表；count(*)表示表中共有多少行。
这些只是一些简单的数据库操作，用来帮助我们i了解数据库和能简单地对数据库进行操作。在下一篇，我们会更深入了解数据库的更多使用！
标签：mysqld connect esc int ase for des admin null
原文地址：https://www.cnblogs.com/liuwentaolaji/p/9689422.html
