Mysql-Basics.pptx

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MYSQL TRAINING

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Mysql =>
• Installation
• Install Multiple Mysql Instances on same host
• Change default location of data files
• Basic Mysql Commands
• Mysqldump
• Restore

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Mysql Installation=>
Mysql installation is based on RPMs that needs to be
installed on the server. Mysql software RPM’s is
available from dev.mysql.com as community version
which can be downloaded as per the OS on which the
installation needs to be done.
http://dev.mysql.com/downloads/mysql
Minimum of 2 RPMs are needed on the server, a server
and client RPM. Without client rpm installation, mysql
server cannot be accessible and hence its mandatory to
get both the rpms installed correctly.

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Install Multiple Instances of Mysql on same
host =>
Mysql services work as a daemon process on a machine. Although it’s
possible to run multiple daemon processes on a machine but it’s not a
official supported way and hence it’s not a recommended configuration
to be done on Production servers.
By giving different my.cnf configuration files with different data
directories, different socket & different port, different pid files we can
configure multiple instance of Mysql.
Regeneron Slave server “renritdb01b.regeneron.regn.com” is an
example of multiple Instances running on a host.

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Here is an example of how multiple Mysql
instances can run on a node.
-bash-3.2$ ps -ef |grep -i mysql
root 6592 1 0 2015? 00:00:00 /bin/sh /usr/bin/mysqld_safe --
datadir=/var/lib/mysql --socket=/var/lib/mysql/mysql.sock --log-
error=/var/log/mysqld.log --pid-file=/var/run/mysqld/mysqld.pid
mysql 11746 1 0 2011 ? 00:00:00 /bin/sh /usr/bin/mysqld_safe --
defaults-file=/opt/mysql5_data/my.cnf --datadir=/opt/mysql5_data/ --
user=mysql --pid-file=/opt/mysql5_data/node1.pid --skip-external-locking --
port=3341 --socket=/tmp/mysql41.sock

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Change default location of Myisam and
Innodb data files
When we do a new installation of mysql server then default data directory is /var/lib/mysql
on Linux OS.
If we need to change default directory to user defined then the steps needs to be
performed.
• Stop mysql services using command like /etc/init.d/mysql stop
• Change following parameters in /etc/init.d/mysql file
Edit the file and check for first occurrence of datadir variable and make changes to it
as below.
datadir=/data01/mysql-data/db
• change below parameters in /etc/my.cnf
datadir=/data01/mysql-data/db
innodb_data_home_dir = /data01/mysql-data/db
• Move all the datafiles from source to target folders
• Start mysql services with /etc/init.d/mysql start

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Basic Commands for checking Mysql is
running fine & for creating db or users=>
• It will tell us if db is working fine or any locks are there
on db & long running queries and the time for which the
process is either active or idle. It also shows the total no
of sessions being connected to the mysql server.
mysql> show processlist;
• Check Mysql is running on Server.
$ ps –ef |grep –i mysql
• Creating a new database
mysql> create database abc;

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• How many db’s are in Mysql Instance
mysql> show databases;
• Create users in Mysql
mysql> create user abc@’localhost’ identified by
'abc'; -- This creates user and allow only local access to the user
mysql> create user abc@’%’ identified by 'abc';
-- This creates user and allow access over the network to the users
mysql> GRANT ALL PRIVILEGES ON DB1.* TO
'abc'@'localhost'; -- Grant all privileges on all the tables on
DB1 database to user which can connect locally.
mysql> GRANT ALL PRIVILEGES ON DB1.* TO
'abc'@'%'; -- Grant all privileges on all the tables on DB1
database to user which can connect locally.

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mysql> GRANT ALL PRIVILEGES ON *.* TO
'abc'@'%'; -- Grant all privileges on all the tables on DB1
database to user which can connect on network.
We need to give below command after creating user so that it can
flush from memory and comes in affect.
mysql> flush privileges;
• Check the slave process status =>
mysql> show slave statusG
There are 3 values to look for in the status:
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Seconds_Behind_Master: 0

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If we need to release that lock we need to kill that ID, check ID for specific lock & kill
that id with kill “id” command.
Mysql> kill “id”;
• Mysql Service Start/Stop
#sudo to mysql
$/etc/init.d/mysql start => for starting
$/etc/init.d/mysql stop => for stopping

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• Delete bin logs from Master when space is full on disk.
Check first how far is slave replication behind its master before purging the binary logs on
master instance:
Run show master status get bin log id
Mysql> show master status;
--Moving to next binary log
Mysql> flush logs;
mysql> Purge binary logs to <binlog from above-1>;
OR
Delete binary logs that are n days old
mysql> PURGE BINARY LOGS BEFORE DATE_SUB(
NOW( ), INTERVAL 2 DAY); -- Deleting all binary logs that are 2 days
old

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• Skipping statements on slave when it’s stopped due to
errors:
mysql> SET GLOBAL sql_slave_statement_skip_counter=1; --
This will skip only the last problematic statement
Storage engines in Mysql:
Mysql daemon process acts as a framework which
can be plugged with one or many storage engines
to create table and store data in it. All storage
engines comes with different characteristics and
before creating a new database or a table it should
be decided in advance that the application is
compatible to which storage engine in mysql.

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Commonly used storage engines in Mysql are as follow:
1. MYISAM =>
MyISAM is the default storage engine. Each MyISAM table is stored on disk in
three files. The files have names that begin with the table name and have an
extension to indicate the file type. An .frm file stores the table format. The data
file has an .MYD (MYData) extension. The index file has an .MYI (MYIndex)
extension.
Properties:
• MyISAM implements table-level lock for inserting and updating.
• MyISAM does not support transactions & foreign keys.
• Also a long running SELECT will also lock the table for other sessions
to access it.
• MyISAM tables are auto commit and hence it cannot be committed or
rolled back.

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2. INNODB:
InnoDB is a transaction-safe storage engine for MySQL that has commit,
rollback, and crash-recovery capabilities to protect user data.
Properties:
• InnoDB row-level locking and Oracle-style consistent no locking
reads increase multi-user concurrency and performance.
• To maintain data integrity, InnoDB also supports FOREIGN KEY
referential-integrity constraints.
• The InnoDB storage engine maintains its own buffer pool for caching
data and indexes in main memory.
• InnoDB stores its tables and indexes in a tablespace, which may
consist of several files (or raw disk partitions). This is different from,
for example, MyISAM tables where each table is stored using separate
files.

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We can create db with storage engine, we can create
table with non default storage engine
mysql> CREATE TABLE t (i INT) ENGINE = INNODB;
&
we can change storage engine of an existing table like
below command,
mysql> Alter table t (i INT) ENGINE =MYISAM;

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How to find current storage engine for a table =>
mysql> show table status like 'onlineregsession'G
*************************** 1. row ***************************
Name: onlineregsession
Engine: MyISAM
Version: 10
Row_format: Dynamic
Rows: 1725842
Avg_row_length: 384
Data_length: 663991508
Max_data_length: 281474976710655
Index_length: 117795840
Data_free: 0
Auto_increment: 1726849
Create_time: 2011-06-11 19:35:03
Update_time: 2012-04-30 02:12:39
Check_time: 2011-06-11 19:36:40
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:

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MYSQL BACKUP & RESTORE
MYSQLDUMP
Mysqldump is a logical backup tool equivalent to exp/imp tool of oracle.
It is used to dump a database or a collection of databases for backup. It
creates a *.sql file with DROP table, CREATE table and INSERT into
sql-statements of the source database. To restore the database, execute
the *.sql file on destination database.
1) Backup a single database
$mysqldump -u root -p[root_password] -–databases [database_name] >
dumpfilename.sql
2) Backup Multiple databases
$mysqldump -u root -p[root_password] --databases db_name1
db_name2 > dumpfilename.sql

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3) Backup all databases containing MyISAM and/or Innodb tables –
CONSISTENT DUMP.
mysql> FLUSH TABLES WITH READ LOCK;
Query OK, 0 rows affected (0.00 sec)
From second session, use below command for backup
$mysqldump --all-databases –single-transaction --master-data=2
>dbdump.db
When backup will be finished then from first session where we acquire
read lock give below command to release locks
mysql> UNLOCK TABLES;
Query OK, 0 rows affected (0.00 sec)
4) Backup all databases containing MyISAM and Innodb tables
– INCONSISTENT DUMP
$mysqldump --all-databases >dbdump.db

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--single-transaction : This option sends a START TRANSACTION SQL
statement to the server before dumping data. It is useful only with
transactional tables such as InnoDB, because then it dumps the
consistent state of the database at the time when BEGIN was issued
without blocking any applications. This is a method for taking a consistent
backup of innodb tables. This option will not take consistent backup of
Myiasm tables. This is not lock any Innodb tables and a consistent backup
can be taken without impacting any production processes.
For taking consistent backup of Myisam tables there are 2 options
available.
• Take a mysql session connecting to the server and run FLUSH
table with read locks. This will lock all the tables on the database with read
lock with no DML operation permitted. From another session take
mysqldump with consistent image. Release the locks from the first
session.

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• If there is a slave configured for primary database, then on
slave perform the following:
Stop the slave process on slave server. Initiate mysqldump, this will be a
consistent backup since no transactions are getting written onto slave.
Once the dump is completed, the again start the slave process.
Restore backup which are taken by mysqldump utility
1. If we took backup of a single database & didn’t use --database
switch while backup then we need to create database before restore
mysql> create database database_name;
$mysql -u root -p[root_password] [database_name] < dumpfilename.sql
2. When took backup with --database switch then no need to create
database manually
$mysql -u root -p[root_password] < dumpfilename.sql

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3. If we have multiple database backup & we need to restore only
one, put db name which we want to restore in restore command
$mysql -u root -p[root_password] dbname < dumpfilename.sql

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Thank You

Mysql-Basics.pptx

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