[bazz2 咩哈哈哈哈哈] 15 Basic MySQL Interview Questions for Database Administrators ================================================================================ Prior to This Article, three articles has already been published in ‘[Linux Interview][1]‘ Section and all of them were highly appreciated by our notable readers, however we were receiving feedback to make this interactive learning process, section-wise. From idea to action, we are providing you **15 MySQL Interview Questions**. ![](http://www.tecmint.com/wp-content/uploads/2013/12/Mysql-Interview-Questions.png) ### 1. How would you check if MySql service is running or not? ### > **Answer** : Issue the command “**service mysql status**” in ‘Debian’ and “**service mysqld status**” in RedHat. Check the output, and all done. root@localhost:/home/avi# service mysql status /usr/bin/mysqladmin Ver 8.42 Distrib 5.1.72, for debian-linux-gnu on i486 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. Server version 5.1.72-2 Protocol version 10 Connection Localhost via UNIX socket UNIX socket /var/run/mysqld/mysqld.sock Uptime: 1 hour 22 min 49 sec Threads: 1 Questions: 112138 Slow queries: 1 Opens: 1485 Flush tables: 1 Open tables: 64 Queries per second avg: 22.567. ### 2. If the service is running/stop how would you stop/start the service? ### > **Answer** : To start MySql service use command as **service mysqld start** and to stop use **service mysqld stop**. root@localhost:/home/avi# service mysql stop Stopping MySQL database server: mysqld. root@localhost:/home/avi# service mysql start Starting MySQL database server: mysqld. Checking for corrupt, not cleanly closed and upgrade needing tables.. ### 3. How will you login to MySQL from Linux Shell? ### > **Answer** : To connect or login to MySQL service, use command: **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> ### 4. How will you obtain list of all the databases? ### > **Answer** : To list all currently running databases run the command on mysql shell as: **show databases**; mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | a1 | | cloud | | mysql | | phpmyadmin | | playsms | | sisso | | test | | ukolovnik | | wordpress | +--------------------+ 10 rows in set (0.14 sec) ### 5. How will you switch to a database, and start working on that? ### > **Answer** : To use or switch to a specific database run the command on mysql shell as: **use database_name**; 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> ### 6. How will you get the list of all the tables, in a database? ### > **Answer** : To list all the tables of a database use the command on mysql shell as: **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) ### 7. How will you get the Field Name and Type of a MySql table? ### > **Answer** : To get the Field Name and Type of a table use the command on mysql shell as: **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) ### 8. How will you delete a table? ### > **Answer** : To delte a specific table use the command on mysql shell as: **drop table table_name**; mysql> drop table lookup; Query OK, 0 rows affected (0.00 sec) ### 9. What about database? How will you delete a database? ### > **Answer** : To delte a specific database use the command on mysql shell as: **drop database database-name**; mysql> drop database a1; Query OK, 11 rows affected (0.07 sec) ### 10. How will you see all the contents of a table? ### > **Answer** : To view all the contents of a particular table use the command on mysql shell as: **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) ### 11. How will you see all the data in a field (say, uid), from table (say, oc_users)? ### > **Answer** : To view all the data in a field use the command on mysql shell as: **select uid from oc_users**; mysql> select uid from oc_users; +-----+ | uid | +-----+ | avi | +-----+ 1 row in set (0.03 sec) ### 12. Say you have a table ‘xyz’, which contains several fields including ‘create_time’ and ‘engine’. The field ‘engine’ is populated with two types of data ‘Memory’ and ‘MyIsam’. How will you get only ‘create_time’ and ‘engine’ from the table where engine is ‘MyIsam’? ### > **Answer** : Use the command on mysql shell as: **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) ### 13. How will you show all the records from table ‘xrt’ where name is ‘tecmint’ and web_address is ‘tecmint.com’? ### > **Answer** : Use the command on mysql shell as: **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 | +---------------+---------------------+----------------+ ### 14. How will you show all the records from table ‘xrt’ where name is not ‘tecmint’ and web_address is ‘tecmint.com’? ### > **Answer** : Use the command on mysql shell as: **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 | +---------------+---------------------+----------------+ ### 15. You need to know total number of row entry in a table. How will you achieve it? ### > **Answer** : Use the command on mysql shell as: **select count(*) from table_name**; mysql> select count(*) from Tables; +----------+ | count(*) | +----------+ | 282 | +----------+ 1 row in set (0.01 sec) That’s all for now. How you feel about this ‘**Linux Interview Question**‘ section. 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