15个 MySQL 基础面试题，DBA 们准备好了吗？

问题1：你如何确定 MySQL 是否处于运行状态？

答案： Debian 上运行命令 service mysql status，在RedHat 上运行命令 service mysqld status。然后看看输出即可。

 

root@localhost:/home/avi# service mysql status/usr/bin/mysqladmin  Ver 8.42 Distrib 5.1.72, for debian-linux-gnu on i486Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.Server version 5.1.72-2Protocol version 10Connection Localhost via UNIX socketUNIX socket /var/run/mysqld/mysqld.sockUptime: 1 hour 22 min 49 secThreads: 1  Questions: 112138  Slow queries: 1  Opens: 1485  Flush tables: 1  Open tables: 64  Queries per second avg: 22.567.

问题2：如何开启或停止 MySQL 服务？

答案：运行命令 service mysqld start 开启服务；运行命令 service mysqld stop 停止服务。

 

root@localhost:/home/avi# service mysql stopStopping MySQL database server: mysqld.root@localhost:/home/avi# service mysql startStarting MySQL database server: mysqld.Checking for corrupt, not cleanly closed and upgrade needing tables..

问题3：如何通过 Shell 登入 MySQL？

答案：运行命令 mysql -u root -p

 

root@localhost:/home/avi# mysql -u root -p Enter password: Welcome to the MySQL monitor.  Commands end with ; or \g. Your MySQL connection id is 207 Server version: 5.1.72-2 (Debian) Copyright (c) 2000, 2013, 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>

问题4：如何列出所有数据库？

答案：运行命令 show databases;

 

mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | a1                 | | cloud              | | mysql              | | phpmyadmin         | | playsms            | | sisso              | | test               | | ukolovnik          | | wordpress          | +--------------------+ 10 rows in set (0.14 sec)

问题5： 如何切换到某个数据库并在上面工作？

答案：运行命令 use database_name; 进入名为 database_name 的数据库。

 

mysql> use cloud; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed mysql>

问题6：如何列出某个数据库内所有表？

答案：在当前数据库运行命令 show tables;

 

mysql> show tables; +----------------------------+ | Tables_in_cloud            | +----------------------------+ | oc_appconfig               | | oc_calendar_calendars      | | oc_calendar_objects        | | oc_calendar_repeat         | | oc_calendar_share_calendar | | oc_calendar_share_event    | | oc_contacts_addressbooks   | | oc_contacts_cards          | | oc_fscache                 | | oc_gallery_sharing         | +----------------------------+ 10 rows in set (0.00 sec)

问题7：如何获取表内所有 Field 对象的名称和类型？

答案：运行命令 describe table_name;

 

mysql> describe oc_users; +----------+--------------+------+-----+---------+-------+ | Field    | Type         | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+-------+ | uid      | varchar(64)  | NO   | PRI |         |       | | password | varchar(255) | NO   |     |         |       | +----------+--------------+------+-----+---------+-------+ 2 rows in set (0.00 sec)

问题8：如何删除表？

答案：运行命令 drop table table_name;

 

mysql> drop table lookup; Query OK, 0 rows affected (0.00 sec)

问题9：如何删除数据库？

答案：运行命令 drop database database-name;

 

mysql> drop database a1; Query OK, 11 rows affected (0.07 sec)

问题10：如何查看表内所有数据？

答案：运行命令 select * from table_name;

 

mysql> select * from engines; +------------+---------+----------------------------------------------------------------+--------------+------+------------+ | ENGINE     | SUPPORT | COMMENT                                                        | TRANSACTIONS | XA   | SAVEPOINTS | +------------+---------+----------------------------------------------------------------+--------------+------+------------+ | InnoDB     | YES     | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        | | 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         | | CSV        | YES     | CSV storage engine                                             | NO           | NO   | NO         | | MEMORY     | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         | | FEDERATED  | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       | | ARCHIVE    | YES     | Archive storage engine                                         | NO           | NO   | NO         | | MyISAM     | DEFAULT | Default engine as of MySQL 3.23 with great performance         | NO           | NO   | NO         | +------------+---------+----------------------------------------------------------------+--------------+------+------------+ 8 rows in set (0.00 sec)

问题11：如何从表（比如 oc_users ）中获取一个 field 对象（比如 uid）的所有数据？

答案：运行命令 select uid from oc_users;

 

mysql> select uid from oc_users; +-----+ | uid | +-----+ | avi | +-----+ 1 row in set (0.03 sec)

问题12：假设你有一个名为 ‘xyz’ 的表，它存在多个字段，如 ‘createtime’ 和 ‘engine’。名为 engine 的字段由 ‘Memoty’ 和 ‘MyIsam’ 两种数值组成。如何只列出 ‘createtime’ 和 ‘engine’ 这两列并且 engine 的值为 ‘MyIsam’？

答案：运行命令 select create_time, engine from xyz where engine = ”MyIsam”;

 

mysql> select create_time, engine from xyz where engine="MyIsam";+---------------------+--------+ | create_time         | engine | +---------------------+--------+ | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-12-15 13:43:27 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | | 2013-10-23 14:56:38 | MyISAM | +---------------------+--------+ 132 rows in set (0.29 sec)

问题13：如何列出表 ‘xrt’ 内 name 域值为 ‘tecmint’，web_address 域值为 ‘tecmint.com’ 的所有数据？

答案：运行命令 select * from xrt where name = “tecmint” and web_address = “tecmint.com”;

 

mysql> select  * from xrt where name = "tecmint" and web_address = “tecmint.com”;+---------------+---------------------+---------------+ | Id                  | name                   | web_address | +---------------+---------------------+----------------+ | 13                 |  tecmint               | tecmint.com  |+---------------+---------------------+----------------+ | 41                 |  tecmint               | tecmint.com  |+---------------+---------------------+----------------+

问题14：如何列出表 ‘xrt’ 内 name 域值不为 ‘tecmint’，web_address 域值为 ‘tecmint.com’ 的所有数据？

答案：运行命令 select * from xrt where name != "tecmint" and web_address = "tecmint.com";

 

mysql> select * from xrt where name != ”tecmint” and web_address = ”tecmint.com”;+---------------+---------------------+---------------+ | Id            | name                | web_address   | +---------------+---------------------+----------------+ | 1173          |  tecmint            | tecmint.com   |+---------------+---------------------+----------------+

问题15：如何知道表内行数？

答案：运行命令 select count(*) from table_name;

 

mysql> select count(*) from Tables; +----------+ | count(*) | +----------+ |      282 | +----------+ 1 row in set (0.01 sec)