Mysql如何創(chuàng)建數(shù)據(jù)庫(kù)

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4.1 create and drop database

C:\Users\admin>mysql -h localhost -u root -pmysql

mysql: [Warning] Using a password on the command line interface can be insecure.

Welcome to the MySQL monitor.  Commands end with ; or \g.

Your MySQL connection id is 3

Server version: 5.7.14 MySQL Community Server (GPL)

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                |

| test               |

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

5 rows in set (0.00 sec)

mysql> create database example;         #create database

Query OK, 1 row affected (0.04 sec)

mysql> show databases;                #顯示databases

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

| Database           |

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

| information_schema |

| example            |

| mysql              |

| performance_schema |

| sys                |

| test               |

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

6 rows in set (0.00 sec)

mysql> drop database example;              #drop database;

Query OK, 0 rows affected (0.04 sec)

mysql> show databases;

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

| Database           |

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

| information_schema |

| mysql              |

| performance_schema |

| sys                |

| test               |

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

5 rows in set (0.00 sec)

mysql> create database mysql;

ERROR 1007 (HY000): Can't create database 'mysql'; database exists

mysql> create database mydata;

Query OK, 1 row affected (0.01 sec)

4.2 存儲(chǔ)引擎

mysql> show engines \G

*************************** 1. row ***************************

      Engine: InnoDB

     Support: DEFAULT

     Comment: Supports transactions, row-level locking, and foreign keys

Transactions: YES

          XA: YES

  Savepoints: YES

*************************** 2. row ***************************

      Engine: MRG_MYISAM

     Support: YES

     Comment: Collection of identical MyISAM tables

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 3. row ***************************

      Engine: MEMORY

     Support: YES

     Comment: Hash based, stored in memory, useful for temporary tables

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 4. row ***************************

      Engine: BLACKHOLE

     Support: YES

     Comment: /dev/null storage engine (anything you write to it disappears)

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 5. row ***************************

      Engine: MyISAM

     Support: YES

     Comment: MyISAM storage engine

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 6. row ***************************

      Engine: CSV

     Support: YES

     Comment: CSV storage engine

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 7. row ***************************

      Engine: ARCHIVE

     Support: YES

     Comment: Archive storage engine

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 8. row ***************************

      Engine: PERFORMANCE_SCHEMA

     Support: YES

     Comment: Performance Schema

Transactions: NO

          XA: NO

  Savepoints: NO

*************************** 9. row ***************************

      Engine: FEDERATED

     Support: NO

     Comment: Federated MySQL storage engine

Transactions: NULL

          XA: NULL

  Savepoints: NULL

9 rows in set (0.00 sec)

mysql>

4.2.1 InnoDB engine

InnoDB是mysql數(shù)據(jù)庫(kù)中的存儲(chǔ)引擎,innodb給mysql的表提供了事務(wù)，回滾，崩潰修復(fù)能力，多版本并發(fā)控制的事務(wù)安全

(1)     Innodb那個(gè)。存儲(chǔ)引擎支持自動(dòng)增長(zhǎng)列auto_increment.

(2)     Innodb存儲(chǔ)引擎支持外鍵(foreign key)

(3)     Innodb存儲(chǔ)引擎，創(chuàng)建的表的表結(jié)構(gòu)在.frm文件中，數(shù)據(jù)和索引存儲(chǔ)在innodb_data_home_dir和innodb_data_file_path定義的表空間

(4)     Innodb存儲(chǔ)引擎的缺點(diǎn)是讀寫(xiě)效率稍差，占用的數(shù)據(jù)空間相對(duì)較大。

4.2.2 MyISAM engine

MyISAM是mysql中常見(jiàn)的存儲(chǔ)引擎

MyISAM存儲(chǔ)引擎的表存儲(chǔ)成三個(gè)文件。文件的名字與表名相同，擴(kuò)展名包括frm,MYD,MYI,

.其中frm為擴(kuò)展名的文件存儲(chǔ)表的結(jié)構(gòu)；MYD(MYData)為擴(kuò)展名的文件存儲(chǔ)數(shù)據(jù)，MYI(MYindex)為擴(kuò)展名的文件存儲(chǔ)引擎

MyISAM存儲(chǔ)引擎的優(yōu)勢(shì)在于占用空間小，處理速度快。缺點(diǎn)是不支持事務(wù)的完整性和并發(fā)性。

4.2.3 MEMORY

特殊存儲(chǔ)引擎,表結(jié)構(gòu)在disk上，數(shù)據(jù)在內(nèi)存中。

Memory表的大小受到顯示，表的大小取決于兩個(gè)參數(shù)max_rows和max_heap_table_size

4.2.4 engines的選擇.

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