在使用MySQL數據庫過程中，有時候會遇到數據庫重復的問題。本文將介紹MySQL數據庫為什么會出現重復數據庫，并提供解決方案。

MySQL數據庫重復是什么意思？當您在MySQL服務器上安裝多個實例時，每個實例都必須有獨特的名稱。實例名稱是當前運行的MySQL服務和與其關聯的數據目錄的標識符。如果您安裝與現有MySQL實例名稱相同的新實例，則會出現重復數據庫。

$ mysql_install_db --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data
Installing MySQL system tables...
191017 10:54:36 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.
191017 10:54:36 [Warning] mysql_install_db is deprecated. Please use mysqld --initialize instead.
191017 10:54:36 [Warning] The syntax '--log' is deprecated and will be removed in a future release. Please use '--general-log[={0|1}]' instead.
OK
Filling help tables...
191017 10:54:36 [Warning] '--skip-locking' is deprecated and will be removed in a future release. Please use '--skip-external-locking' instead.
191017 10:54:36 [Warning] mysql_install_db is deprecated. Please use mysqld --initialize instead.
To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system
PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:
/usr/local/mysql/bin/mysqladmin -u root password 'new-password'
/usr/local/mysql/bin/mysqladmin -u root -h myhost password 'new-password'
See the manual for more instructions.
You can start the MySQL daemon with:
cd /usr/local/mysql ; /usr/local/mysql/bin/mysqld_safe &
You can test the MySQL daemon with mysql-test-run.pl
Please report any problems at http://bugs.mysql.com/
The latest information about MySQL is available on the web at
http://www.mysql.com
Support MySQL by buying support/licenses at http://shop.mysql.com
New default config file was created as /usr/local/mysql/my.cnf and
will be used by default by the server when you start it. You may
edit this file to change server settings
WARNING: Default config file /etc/my.cnf exists on the system
This file will be read by default by the MySQL server
If you do not want to use this, either remove it, or use the
--defaults-file argument to mysqld_safe when starting the server

如上所示，當我們在MySQL系統上創建新實例時，我們可以看到警告信息，提示mysql_install_db過時，應改用mysqld --initialize代替。此外，有許多其他選項可用于自定義安裝過程，例如指定MySQL數據目錄的位置等。

為了避免出現重復數據庫，我們應該始終為新實例命名唯一的名稱，并且要確保new-instance-name不與任何其他實例名稱相同。如果在安裝MySQL時沒有為實例指定名稱，則系統將默認創建名為mysql的實例。

$ mysqld --initialize-insecure --datadir=/usr/local/mysql/data --basedir=/usr/local/mysql --socket=/tmp/mysql.sock

除此之外，我們可以通過以下方式來查看MySQL的實例信息：

$ ps aux | grep mysqld

MySQL數據庫中出現重復的問題并不是太難解決。只要我們在創建新實例時記得為實例命名唯一的名稱，并同時確保避免與其他實例名稱相同，就能夠避免重復數據庫的問題。