mysql8基础 drop database if exists... 若数据库存在则删除

•        OS : Ubuntu 18.04.1 LTS
•        DBMS : mysql 8.0.12
•        blog : blog.csdn.net/shiwanwu
•  typesetting : Markdown

 

数据，数据，命根就在数据 ! 操作数据库时，一定要谨慎小心。师万物 的代码看看就好，要有自己的判断。遇到抉择，要不耻上下问。

 

example

stu@Ubuntu:~$ mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 92
Server version: 8.0.12 MySQL Community Server - GPL

Copyright (c) 2000, 2018, 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           |
+--------------------+
| db_herbal_medicine |
| employees          |
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
6 rows in set (0.00 sec)

mysql> drop database if exists db_herbal_medicine;
Query OK, 0 rows affected (0.08 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| employees          |
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> drop database if exists db_herbal_medicine;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> exit
Bye
stu@Ubuntu:~$ 

 

more knowledge

• 在[1]中提到的：“先通过drop database if exists aa试图删除一个不存在的数据库aa，系统出现提示1warning，此时通过show warnings查询显示的是empty set；”。
• 基于MySQL8进行测试，结果如下所示：

stu@Ubuntu:~$ mysql -u root -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 93
Server version: 8.0.12 MySQL Community Server - GPL

Copyright (c) 2000, 2018, 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           |
+--------------------+
| employees          |
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> drop database if exists db_herbal_medicine;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show warnings;
Empty set (0.00 sec)

mysql> \W
Show warnings enabled.
mysql> drop database if exists db_herbal_medicine;
Query OK, 0 rows affected, 1 warning (0.00 sec)

Note (Code 1008): Can't drop database 'db_herbal_medicine'; database doesn't exist
mysql> \w
Show warnings disabled.
mysql> exit
Bye
stu@Ubuntu:~$ 

• 如果哪位前辈明白其中的原因，还请指点一二。O(∩_∩)O谢谢

 

reference

• [1] https://segmentfault.com/q/1010000011801759

 

resource

• [手册] dev.mysql.com/doc
• [源码] downloads.mysql.com/archives/community
• [Bug ] bugs.mysql.com
• [ 测试数据 ] github.com/datacharmer/test_db
• [规范 - 参考] yq.aliyun.com/articles/69327
• [排名 - 参考] db-engines.com/en
• [平台] www.csdn.net

 

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MySQL是关系型数据库管理系统，目前是开源的(2019-02)。
明确权限，恰当地选择引擎与字符集等，规范命名。
MariaDB，Redis，MongoDB，PostgreSQL，Hive，HBase等，多作了解，拓宽心量。
Workbench，phpMyAdmin，Navicat等图形化管理工具，豫兮若冬涉川。