MySQL数据库管理 | 易学教程

Mysql管理操作

数据库管理操作

查看数据库结构
创建及删除库和表
管理表的记录

基本操作命令

查看数据库列表信息
- SHOW DATABASES

[root@localhost ~]# 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 Source distribution

Copyright (c) 2000, 2016, 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> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

查看数据库中的数据表信息
- USE数据库名
- SHOW TABLES

mysql> use mysql
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_mysql           |
+---------------------------+
| columns_priv              |
| db                        |
| engine_cost               |
| event                     |
| .....                     |
| user                      |
+---------------------------+
31 rows in set (0.00 sec)

显示数据表的结构（字段）
- DESCRIBE [数据库名.]表名

mysql> describe db;
+-----------------------+---------------+------+-----+---------+-------+
| Field                 | Type          | Null | Key | Default | Extra |
+-----------------------+---------------+------+-----+---------+-------+
| Host                  | char(60)      | NO   | PRI |         |       |
| Db                    | char(64)      | NO   | PRI |         |       |
| User                  | cha(32)      | NO   | PRI |         |       |
| Select_priv           | enum('N','Y') | NO   |     | N       |       |
| Execute_priv          | enum('N','Y') | NO   |     | N       |       |
| ...                                                                  |
| Trigger_priv          | enum('N','Y') | NO   |     | N       |       |
+-----------------------+---------------+------+-----+---------+-------+
22 rows in set (0.00 sec)

SQL语句概述

SQL语言

是Structured Query Language的缩写，即结构化查询语言
是关系型数据库的标准语言
用于维护管理数据库,如数据查询、数据更新、访问控制、对象管理等功能

SQL分类

DDL：数据定义语言
DML：数据操纵语言
DQL：数据查询语言
DCL：数据控制语言

DDL语句操作

DDL语句用于创建数据库对象，如库、表、索引等
使用DDL语句新建库、表
- 创建数据库: CREATE DATABASE 数据库名
- 创建数据表: CREATE TABLE 表名（字段定义...）

mysql> create database school;
Query OK, 1 row affected (0.00 sec)

mysql> use school;
Database changed
mysql> create table info (
    -> id int(4) ,
    -> name char(10) not null,
    -> address varchar(50) default 'nanjing',
    -> primary key (id));
Query OK, 0 rows affected (0.01 sec)

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

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

DDL语句操作

使用DDL语句删除库、表
- 删除指定的数据表: DROP TABLE [数据库名.]表名
- 删除指定的数据库: DROP DATABASE 数据库名

mysql> drop table info;
Query OK, 0 rows affected (0.00 sec)

mysql> show tables;
Empty set (0.00 sec)

mysql> drop database school;
Query OK, 0 rows affected (0.00 sec)

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

DML语句操作

DML语句用于对表中的数据进行管理
包括以下操作
- INSERT:插入新数据
- UPDATE :更新原有数据
- DELETE :删除不需要的数据

mysql> create database school;
Query OK, 1 row affected (0.01 sec)

mysql> use school;
Database changed
mysql> create table info ( 
    -> id int(4) not null,
    -> name char(10) not null,
    -> address varchar(50) default 'nanjing',
    -> primary key (id));
Query OK, 0 rows affected (0.00 sec)

mysql> insert into info (id,name,address) values (1,'zhangsan','beijing');
Query OK, 1 row affected (0.01 sec)

mysql> select * from info;       //查看表所有内容
+----+----------+---------+
| id | name     | address |
+----+----------+---------+
|  1 | zhangsan | beijing |
+----+----------+---------+
1 row in set (0.00 sec)

mysql> update info set address='shanghai' where id=1;    //将info表内id为1的address更改为shanghai
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from info;              //查看表内容
+----+----------+----------+
| id | name     | address  |
+----+----------+----------+
|  1 | zhangsan | shanghai |
+----+----------+----------+
1 row in set (0.00 sec)

mysql> delete from info where id=1;     //根据条件删除info表中id为1的数据，不带where条件时删除表内所有数据
Query OK, 1 row affected (0.00 sec)

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

DQL语句操作

DQL是数据查询语句，只有一条: SELECT
用于从数据表中查找符合条件的数据记录
查询时可不指定条件
- SELECT 字段名1,字段名2.... FROM表名

mysql> select * from info;       //查看表所有内容
+----+----------+---------+
| id | name     | address |
+----+----------+---------+
|  1 | zhangsan | beijing |
+----+----------+---------+
1 row in set (0.00 sec)

mysql> select name from info where id=1;      //条件查看表内容
+----------+
| name     |
+----------+
| zhangsan |
+----------+
1 row in set (0.00 sec)