Beginners are always searching for sample database so, in this post, I am sharing an official download link to a MySQL Sakila sample database which we can use for our testing purpose.

Sakila sample database is a DVD rental database. The database contains sample tables, views, SPs, Functions and Triggers.

The MySQL beginner can install this database and can start the practice with it.
PostgreSQL beginner can also use this database.

Please check the official page here, and you can see all require documentation like, database structure, installation steps.

In this post, I am sharing a script for checking the size of Database and Tables in MySQL.

MySQL: Script to find total occupied Size of each Storage Engines

MySQL: Script to find Largest Databases size on Server

Find the size of Database:

SELECT 
	table_schema AS Database_Name
	,ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) AS SizeInMB
FROM information_schema.tables
GROUP BY table_schema

Find the size of Table:

SELECT 
	table_name AS TableName
	,ROUND(((data_length + index_length) / 1024 / 1024), 2) AS SizeInMB
FROM information_schema.TABLES
WHERE table_schema = 'Database_NAME'
AND table_name = 'Table_Name'

In this post, I am sharing a command to swap the table in a MySQL Database.

Recently, I got a requirement like a swap or rename the table, it should execute in a lock/transaction. People can access the table before or after the swapping only.

In an ETL/Database work, we are creating a staging table for validation and later it requires to overwrite with an original table name.

Below is a simple command, which you can use for this task:
Here, DBRND_Original is an existing table and DBRND_Original_New is my staging table.
Now, I am swapping the table using one rename command which performs whole swapping operation in one transaction.

RENAME TABLE DBRND_Original TO DBRND_Original_Backup, DBRND_Original_New To DBRND_Original;

In this post, I am sharing a script to find all the tables without having a Primary Key in MySQL.

This script is very important because Primary Key is a one of a major part of the table. I never recommended like creating a table without Primary Key.

Using below script, and find the tables that do not have a primary key:

select 
	table_schema
	,table_name
from information_schema.columns
where table_schema = 'SCHEMA_NAME'
group by 
	table_schema
	,table_name
having sum(if (column_key in ('PRI', 'UNI'), 1, 0)) = 0

After successful installation MySQL Server, Have you ever suffer any problem in connecting the Database? If you are not able to connect MySQL, there are multiple reasons.

One is MySQL service may not configure in services.msc. In this post, I am sharing steps on how to install/configure MySQL Service.

Step 1:
Check the services.msc (open by pressing Windows key + R and write services.msc)
If service is not present, follow two steps.

Step 2:
Open Windows Command Prompt as an Administrator

Step 3:
Go to ../MySQL Server 5.7/bin

Step 4: Install MySQL Service

mysqld --install

Step 5: Initialize MySQL Service

mysqld --initialize

Step 6:
Now, MySQL Service is installed and configured so open services.msc and check the status.

In this post, I am sharing full steps on how to reset the forgotten MySQL ROOT password in Windows Operating System.

When you are installing MySQL, it asks for setting up a ROOT Password which the default admin setup of your MySQL Server.
I noticed that most of the people are forgetting the main ROOT password of MySQL and then You can’t connect to server/database.

I found multiple solutions, but here I am sharing two solutions.

One solution is given by MySQL Developer, for that please visit this link:

For alternative, please follow below steps:

How to reset MySQL root Password in Ubuntu

Step 1:
Go to services.msc and stop the MySQL Service

Step 2:
Open Windows Command Prompt as an Administrator

Step 3:
Go to ../MySQL Server 5.7/bin/

Step 4: Execute this command

mysqld.exe -u root --skip-grant-tables

Step 5: Start the MySQL Service

Step 6:
Open a new Windows Command Prompt as an Administrator and go to MySQL/bin

Step 7:
Type MySQL and press enter. Now, you are in MySQL Console.

Step 8: Reset the password

UPDATE user SET Password = PASSWORD('New_Password') WHERE User = 'root';

In this post, I am sharing different types of options to copy your MySQL Database from one server to another server.

The migration of data, objects or database is a ubiquitous task for any DBA so as a blogger I can’t skip this kind of topics.

Common and General option:

Server 1: Take the backup in .sql file
– -databases option adds the CREATE DATABASE in dump file, so that you can restore same backup in any other server without creating a blank database.

my-shell> mysqldump --databases db_name > mydump.sql

Next, copy mydump.sql file from Server 1 to Server 2.

Server 2: Restore the backup

my-shell> mysql < mydump.sql

My favourite option:

Use pipe and copy the database from one server to another, without taking or moving the physical file.

mysqldump -uuser -ppassword db_name | mysql -hremoteserver -uremoteuser -premoteserverpassword

For all database:

mysqldump --all-databases -uuser -ppassword | mysql -hremoteserver -uremoteuser -premoteserverpassword

In this post, I am showing the installation process of MySQL Tuner in Ubuntu 16.04.
MySQL Tuner is a useful tool that will connect to a running MySQL instance and offer suggestions for how it can be configured for your workload.

You can use this tool for running production server as well, and it will give you different types of Performance Metrics and Server statistics like about the Storage, Security, Performance Parameters, Cache Parameters, InnoDB Settings, MyISAM Settings and more.

Install MySQL Tuner in Ubuntu 16.04:

sudo apt-get install mysqltuner

Execute MySQL Tuner:

mysqltuner

Here, I am also sharing the sample result of my test server on which I installed and executed MySQL Tuner.

-------- Storage Engine Statistics -------------------------------------------
[--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MRG_MYISAM
[--] Data in InnoDB tables: 16K (Tables: 1)
[OK] Total fragmented tables: 0

-------- Security Recommendations  -------------------------------------------
[OK] There is no anonymous account in all database users
ERROR 1054 (42S22) at line 1: Unknown column 'password' in 'where clause'
[OK] All database users have passwords assigned
ERROR 1054 (42S22) at line 1: Unknown column 'password' in 'where clause'

-------- Performance Metrics -------------------------------------------------
[--] Up for: 4d 17h 35m 56s (26 q [0.000 qps], 32 conn, TX: 21K, RX: 5K)
[--] Reads / Writes: 100% / 0%
[--] Binary logging is disabled
[--] Total buffers: 192.0M global + 1.1M per thread (151 max threads)
[OK] Maximum reached memory usage: 194.1M (19.60% of installed RAM)
[OK] Maximum possible memory usage: 352.4M (35.58% of installed RAM)
[OK] Slow queries: 0% (0/26)
[OK] Highest usage of available connections: 1% (2/151)
[!!] Aborted connections: 43.75%  (14/32)
[!!] Query cache is disabled
[OK] Temporary tables created on disk: 15% (10 on disk / 64 total)
[OK] Thread cache hit rate: 93% (2 created / 32 connections)
[OK] Table cache hit rate: 25% (28 open / 109 opened)
[OK] Open file limit used: 0% (6/1K)
[OK] Table locks acquired immediately: 100% (100 immediate / 100 locks)

-------- MyISAM Metrics -----------------------------------------------------
[!!] Key buffer used: 18.2% (3M used / 16M cache)
[OK] Key buffer size / total MyISAM indexes: 16.0M/43.0K
[!!] Read Key buffer hit rate: 50.0% (6 cached / 3 reads)

-------- InnoDB Metrics -----------------------------------------------------
[--] InnoDB is enabled.
[OK] InnoDB buffer pool / data size: 128.0M/16.0K
[OK] InnoDB buffer pool instances: 1
[!!] InnoDB Used buffer: 3.55% (291 used/ 8191 total)
[!!] InnoDB Read buffer efficiency: 81.34% (1120 hits/ 1377 total)
[!!] InnoDB Write buffer efficiency: 0.00% (0 hits/ 1 total)
[OK] InnoDB log waits: 0.00% (0 waits / 2 writes)

-------- AriaDB Metrics -----------------------------------------------------
[--] AriaDB is disabled.

-------- Replication Metrics -------------------------------------------------
[--] No replication slave(s) for this server.
[--] This is a standalone server..

When you install the MySQL, the root user is a default, and even most of the people also set the password ‘root’.

For MySQL, username and password like root-root is a very common so hackers can easily try this combination and can attack in your database system.

After the installation of MySQL Server, please don’t forget to rename the name of the root user.
In this post, I am sharing required steps for changing the name of the root user.

Connect MySQL and check the list of users:

mysql> select user,host from mysql.user;
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| debian-sys-maint | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+

Rename the ‘root’ user to ‘anvesh’:

rename user 'root'@'localhost' to 'anvesh'@'localhost';

Confirm the new user name:

mysql> select user,host from mysql.user;
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| anvesh           | localhost |
| debian-sys-maint | localhost |
| mysql.sys        | localhost |
+------------------+-----------+

Now, flush the privileges to make these changes happen:

FLUSH PRIVILEGES;

Now, connect with new user name:

mysql -u anvesh -p

In this post, I am sharing required steps to move MySQL Data Directory from old location to new location.

Check the current data directory of MySQL:

mysql> select @@datadir;
+-----------------+
| @@datadir       |
+-----------------+
| /var/lib/mysql/ |
+-----------------+

Stop the MySQL Service:

sudo systemctl stop mysql

Confirm the inactive status of MySQL Service:

sudo systemctl status mysql

● mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: inactive (dead) since Wed 2017-07-12 19:45:48 UTC; 11s ago
 Main PID: 8841 (code=exited, status=0/SUCCESS)

Jul 12 19:11:30 ip-172-31-27-19 systemd[1]: Starting MySQL Community Server...
Jul 12 19:11:31 ip-172-31-27-19 systemd[1]: Started MySQL Community Server.
Jul 12 19:45:46 ip-172-31-27-19 systemd[1]: Stopping MySQL Community Server...
Jul 12 19:45:48 ip-172-31-27-19 systemd[1]: Stopped MySQL Community Server.

Use rsync with -av flag to copy the existing database directory to the new location:

sudo rsync -av /var/lib/mysql /mnt/dbrnd_mysql

Rename old MySQL Data Directory:

sudo mv /var/lib/mysql /var/lib/mysql.backup

Change (datadir=) parameter in MySQL Config file (mysqld.cnf) for pointing to the New Data Location:

sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /mnt/dbrnd_mysql/mysql
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

Now, Check below sample error:

Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for details.

To avoid above error, configure AppArmor Access Control Rules:

AppArmor: AppArmor (“Application”) is a Linux kernel security module that allows the system administrator to restrict programs’ capabilities with per-program profiles. Profiles can allow capabilities like network access, raw socket access, and the permission to read, write, or execute files on matching paths.

Open AppArmor for edit:

sudo nano /etc/apparmor.d/tunables/alias

Add new entry of new data location path:

alias /var/lib/mysql/ -> /mnt/volume-nyc1-01/mysql/,

# ------------------------------------------------------------------
#
#    Copyright (C) 2010 Canonical Ltd.
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of version 2 of the GNU General Public
#    License published by the Free Software Foundation.
#
# ------------------------------------------------------------------

# Alias rules can be used to rewrite paths and are done after variable
# resolution. For example, if '/usr' is on removable media:
# alias /usr/ -> /mnt/usr/,
#
# Or if mysql databases are stored in /home:
# alias /var/lib/mysql/ -> /var/lib/mysql/,
alias /var/lib/mysql/ -> /mnt/dbrnd_mysql/mysql/,

After change, restart the AppArmor:

sudo systemctl restart apparmor

Create the minimal directory structure:

sudo mkdir /var/lib/mysql/mysql -p

Now, Start the MySQL Service:

sudo systemctl start mysql

Check the status of MySQL Service:

sudo systemctl status mysql

Now, connect MySQL and check the new datadir location:

mysql> select @@datadir;
+-------------------------+
| @@datadir               |
+-------------------------+
| /mnt/dbrnd_mysql/mysql/ |
+-------------------------+