第一章 基本操作

创建数据库

mysql> create database example;

Query OK, 1 row affected

查看已存在的数据库：

mysql> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| MyCloudDB |

| example |

| mydatabase |

| mysql |

| performance_schema |

| sampledb |

| user_db |

+--------------------+

8 rows in set

删除数据库

mysql> drop database example;

Query OK, 0 rows affected

数据库存储引擎

查看支持的存储引擎

mysql> show engines;

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

| Engine | Support | Comment | Transactions | XA | Savepoints |

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

| MyISAM | YES | MyISAM storage engine | NO | NO | NO |

| CSV | YES | CSV storage engine | NO | NO | NO |

| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |

| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |

| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |

| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |

| ARCHIVE | YES | Archive storage engine | NO | NO | NO |

| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |

| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |

+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

9 rows in set

MyISAM和InnoDB存储引擎的区别

	MyISAM	InnoDB
构成	由表定义文件、数据文件和索引文件构成	由表空间数据文件和日志文件构成
事务	不支持	支持
操作	SELECT操作性能更好	INSERT和UPDATE性能更好
表的具体行数	select count(*) from table,MyISAM只要简单的读出保存好的行数， 注意的是，当count(*)语句包含   where条件时，两种表的操作是一样的	InnoDB 中不保存表的具体行数，也就是说，执行select count(*) from table时，InnoDB要扫描一遍整个表来计算有多少行
锁	表锁	提供行锁，提供不加锁读取，另外，InnoDB表的行锁也不是绝对的，如果在执行一个SQL语句时MySQL不能确定要扫描的范围，InnoDB表同样会锁全表，例如update table set num=1 where name like “%aaa%”

InnoDB和Myisam区别点击这里。

查看默认存储引擎

mysql> show variables like 'storage_engine';

+----------------+--------+

| Variable_name | Value |

+----------------+--------+

| storage_engine | InnoDB |

+----------------+--------+

1 row in set