目录
一、数据库概述
1. SQL分类
- DDL【Data Definition Language】数据定义语言,用来维护存储数据的结构,如:create、drop、alter
- DML【Data Manipulation Language】数据操纵语言,用来对数据进行操作,如:insert、delete、update、select(由DML有细分为DQL负责查询)
- DCL【Data Control Language】数据控制语言,负责权限管理和事务,如:grant、revoke、commit
2. 存储引擎
存储引擎定义:数据库管理系统如何存储数据、如何为存储的数据建立索引和如何更新、查询数据等技术的实现方法。
MySQL的核心就是插件式存储引擎,支持多种存储引擎,InnoDB是默认存储引擎。
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)