15 Basic MySQL Interview Questions for Database Administrators

Prior to This Article, three articles has already been published in ‘Linux Interview‘ 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.

1. How would you check if MySql service is running or not?

[email protected]:/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?

[email protected]:/home/avi# service mysql stop
Stopping MySQL database server: mysqld.
[email protected]:/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?

[email protected]:/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?

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?

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?

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?

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?

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

9. What about database? How will you delete a database?

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

10. How will you see all the contents of a table?

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)?

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’?

12. 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’?

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’?

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?

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

Read Also : 10 MySQL Database Interview Questions Intermediates

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