MariaDB Interview Questions & Answers

Download PDF

The 'MySQL' name is trademarked by Oracle, and they have chosen to keep that trademark to themselves. The name MySQL (just like the MyISAM storage engine) comes from Monty's first daughter "My". MariaDB continues this tradition by being named after his younger daughter, Maria.

Percona’s pt-table-checksum is the preventative tool to use
It can build checksums of all your tables, and then propagate those checksums through replication to the slave.

No need for a fresh install.

Just export your data, move or delete the system database (ibdata1) and the log files (ib_logfile0 & ib_logfile1), set innodb_page_size to either 4k or 8k, and restart MariaDB. A new XtraDB instance will be created with the smaller page size. Then you can import your data and run your tests.

First, you have to create a database in MariaDB follows by selecting the database and then create a table by using CREATE TABLE statement.

Syntax:
CREATE TABLE table_name (column_name column_type);

MariaDB DISTINCT Clause is used to remove duplicates from the result when it is used with SELECT statement.

Syntax:
SELECT DISTINCT expressions
FROM tables
[WHERE conditions];

DROP DATABASE command is used to drop a database in MariaDB.

Syntax:
DROP DATABASE Database_name;

MariaDB AVG() function is used to retrieve the average value of an expression.

Syntax:
SELECT AVG(aggregate_expression)
FROM tables
[WHERE conditions];

JOIN is used to retrieve data from two or more tables. By default JOIN is also called INNER JOIN. It is used with SELECT statement.

There are mainly two types of joins in MariaDB:
☛ INNER JOIN
☛ OUTER JOIN

Again OUTER JOIN is divided in two types:
☛ LEFT JOIN
☛ RIGHT JOIN

The data directory location is controlled by the datadir variable. Look at your /etc/mysql/my.cnf file to see where your installation of MariaDB is configured to store data. The default is /var/lib/mysql but it is often changed, like for example if you are using a RAID array.

USE DATABASE command is used to select and use a database in MariaDB.

Syntax:
USE database_name;

MariaDB LIKE clause is used with SELECT, INSERT, UPDATE and DELETE statement to retrieve data when an operation needs an exact match.

Syntax:
SELECT field, field2,... FROM table_name, table_name2,...
WHERE field LIKE condition

MariaDB RIGHT OUTER JOIN is used to return all rows from right-hand table specified in the ON condition and only those rows from the other table where the joined fields are satisfied the conditions.

MariaDB RIGHT OUTER JOIN is also called RIGHT JOIN.

Syntax:
SELECT columns
FROM table1
RIGHT [OUTER] JOIN table2
ON table1.column = table2.column;

MariaDB ORDER BY Clause is used to sort the records in your result set in ascending or descending order.

Syntax:
SELECT expressions
FROM tables
[WHERE conditions]
ORDER BY expression [ ASC | DESC ];

InnoDB/XtraDB tables can be up to 64TB (terabytes) in size. On top of this you can have multiple tables per database and multiple databases per server. Usually the size and space limits of your underlying storage and operating system are reached long before MariaDB's internal limits are reached.

DROP TABLE command is used to delete a table from a database in MariaDB. It deletes the table permanently and cannot be recovered.

Syntax:
DROP TABLE table_name ;

FROM clause is used with SELECT statement to retrieve data from the table. It is also used to join tables.

Syntax:
SELECT columns_names FROM table_name;

☛ InnoDB Becomes Default Storage Engine
☛ Semi-Synchronous Replicatio
☛ Improved Recovery Performance
☛ InnoDB Stats in Performance Schema
☛ Multiple Buffer Pool Instances
☛ More Partitioning Options

or MariaDB 5.3.x then you can uninstall MariaDB with:

sudo make uninstall

If you compiled and installed MariaDB 5.5.x or higher then there is no 'make uninstall'. However, after doing a 'sudo make install' to install MariaDB there will be an 'install_manifest.txt' file at the top level of the source dir. Remove all of the files listed in it and everything you installed will be gone.

On Linux the default is to place everything under '/usr/local/mysql/' so removing that directory is enough to uninstall MariaDB. If you customized the install directory, or if MacOS has a different default then it will be different. In any case the 'install_manifest.txt' file will have the locations.

CREATE DATBASE command is used to create database in MariaDB.

Syntax:

CREATE DATABASE Database_name;

SELECT statement is used to retrieve records from a table in MongoDB database. You can choose, single, multiple or all records from a table by using different keywords.

Syntax:
SELECT expressions
FROM tables
[WHERE conditions];

MariaDB MAX() function is used to retrieve the maximum value of the expression.

Syntax:
SELECT MAX(aggregate_expression)
FROM tables
[WHERE conditions];

Allow them to talk about their experiences and how it has shaped their career.
Historically MySQL DBA are created out of their work experience. Some are focused on System administration while others are Web Developers, sometimes they are all of the above. Either way they now have a focus on the MySQL database and you might be able to use that experience to your advantage.

MariaDB MIN() functiuon is used to retrieve the minimum value of the expression.

Syntax:
SELECT MIN(aggregate_expression)
FROM tables
[WHERE conditions];

The MariaDB DELETE statement is used to delete one or more records from the table in the database. It can be used to delete records from the table as well the whole table if you use it without WHERE condition.

Syntax:
DELETE FROM table
[WHERE conditions]
[ORDER BY expression [ ASC | DESC ]]
[LIMIT number_rows];

MariaDB Galera Cluster is a synchronous multi-master cluster for MariaDB. It is available on Linux only, and only supports theXtraDB/InnoDB storage engines (although there is experimental support for MyISAM - see the wsrep_replicate_myisam system variable).

Starting with MariaDB 10.1, the wsrep API for Galera Cluster is included by default. This is available as a separate download for MariaDB 10.0 and MariaDB 5.5.