MySQL系列:数据库基本操作(1)

1. 登录数据库

mysql -h localhost -u root -p

2. 数据库基本操作

2.1 查看数据库

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sakila             |
| sys                |
| world              |
+--------------------+
6 rows in set (0.00 sec)

2.2 创建数据库

mysql> CREATE DATABASE db;
mysql> CREATE DATABASE IF NOT EXISTS db;

  指定字符集:

mysql> CREATE DATABASE db CHARACTER SET 'utf8' COLLATE 'utf8_general_ci';

2.3 查看创建数据库定义

mysql> SHOW CREATE DATABASE db G;
*************************** 1. row ***************************
       Database: db
Create Database: CREATE DATABASE `db` /*!40100 DEFAULT CHARACTER SET utf8 */
1 row in set (0.00 sec)

2.4 使用数据库

mysql> USE db;

2.5 显示使用的数据库

mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| db         |
+------------+

2.6 删除数据库

mysql> DROP DATABASE db;

3. 查看数据库系统支持的存储引擎类型

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       |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

  其中,Support中DEFAULT表示默认存储引擎。

3.1 InnoDB存储引擎

  InnoDB事务型数据库的首选引擎,支持事务安全表(ACID),支持行锁和外键。MySQL5.5.5之后,InnoDB作为默认存储引擎。

  InnoDB存储引擎中,创建的表的表结构存储在.frm文件中数据和索引存储在innodb_data_home_dir和innodb_data_file_path定义的表空间中

  使用InnoDB时,MySQL将在数据目录下创建ibdata1的自动扩展数据文件,以及两个ib_logfile0和ib_logfile1的日志文件。

  innodb_data_file_path:指定innodb tablespace文件。如果不在my.ini文件中指定innodb_data_home_dir和innodb_data_file_path,则默认会在datadir目录下创建ibdata1 作为innodb tablespace。

[mysqld]

#Path to the database root
datadir="C:/ProgramData/MySQL/MySQL Server 5.6/Data/"

  查询innodb_data_home_dir和innodb_data_file_path参数设置:

mysql> SHOW VARIABLES LIKE 'innodb_data%';
+-----------------------+------------------------+
| Variable_name         | Value                  |
+-----------------------+------------------------+
| innodb_data_file_path | ibdata1:12M:autoextend |
| innodb_data_home_dir  |                        |
+-----------------------+------------------------+

  my.ini中设置innodb_data_home_dir和innodb_data_file_path参数:

[mysqld]

innodb_data_home_dir = /data/3306
innodb_data_file_path = ibdata1:12M:autoextend:max:1G

3.2 MyISAM存储引擎

  MyISAM具有较高的插入、查询速度,但不支持事务。MySQL5.5.5之前为默认存储引擎。

  MyISAM存储引擎的表存储成3个文件,文件名称与表名相同,扩展名包括frm、MYD和MYI。其中,frm扩展名文件存储表的结构,MYD扩展名文件存储数据(MYData缩写),MYI扩展名文件存储索引(MYIndex缩写)。

  MyISAM存储引擎的优点:占用空间小,处理速度快;缺点:不支持实务的完整性和并发性。

4. 查询默认存储引擎

mysql> show variables like 'storage_engine';
+----------------+--------+
| Variable_name  | Value  |
+----------------+--------+
| storage_engine | InnoDB |
+----------------+--------+
1 row in set (0.00 sec)

  可以在my.ini中修改默认存储引擎,将“default-storage-engine=INNODB”改为“default-storage-engine=MyISAM”,重启服务,修改生效。

5. 查看数据库字符集

mysql> SELECT DISTINCT table_schema,table_collation
    -> FROM information_schema. TABLES
    -> WHERE table_schema NOT IN ('performance_schema', 'sys', 'test', 'mysql', 'information_schema');
+--------------+-----------------+
| table_schema | table_collation |
+--------------+-----------------+
| db           | utf8_general_ci |
+--------------+-----------------+
原文地址:https://www.cnblogs.com/libingql/p/6388360.html