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A Brief Introduction to MySQL
What is MySQL ? Its good features.
Security and Privilege System
Compatibility with standards
Locks – an interesting feature
Some more salient features
What Is MySQL?
A fast, reliable, easy-to-use, multi-user multi-
threaded relational database system.
It is freely available and released under GPL
(GNU General Public License ).
Why Use MySQL ?
MySQL server can handle very large
Offers rich and very useful set of functions.
Connectivity, speed and security make MySQL
very suited for accessing database on a
A lot of contributed software available.
What Does MySQL Offer ?
A privilege and password system that is very
flexible and secure and allows host-based
Multi-threaded request-handling using kernel
Very actively developed.
Memory leak proof.
Quick Installation Guide
• tar –zxvf Mysql.x.xx.xx.tar.gz
Mysql –u root password ‘mypassword’
--bindir=Dir specifies dir for binaries
--localstatedir=Dir data dir
--with-charset=charset (default Latin1)
Works on many different platforms like
FreeBSD , NetBSD , Linux 2.0+, Windows ’95,
’98, 2000 & NT, HP-UX etc
There are client tools and APIs available in c,
c++, java, perl, python, php, Tcl
Security in mysql
Issues that bother: eavesdropping,altering
Uses ACL’s (Access Control Lists) , also
there’s some support for SSL connections
Has inbuilt methods for storing confidential
data like passwords in encrypted form.
Access is restricted thru grant of privileges to
Privileges provided by mysql
The five tables:
The privileges come into play only if there is a
retrieval of data from the database, or updation
of data in the database,e.g:
select 1+1; calculator
File privilege : load data infile, select …. Into
How the privilege system works
First reference to user followed by db and host , takes
place during connection verification
Reference to tables_priv and columns_priv at data
Ordering of user table on the basis of more specific
host values first, followed by more specific user values.
For security purposes , mysql disallows host
addresses of the form :192.168.7.yahoo.com
Some tips on security
Beneficial to invest in a firewall ; check using “telnet
Do not rely on the data entered by the user, he can
trick the code by using special character sequences
Make use of tcpdump, to check the whether or not
mysql data streams r unencrypted:
tcpdump –l –i eth0 –w – src port 3306|strings
Dont run mysqld as root.
Don’t give process and file privileges to users as far as
Following mysqld options affect security:
1. –- secure 2. – skip-grant-privileges
3. – skip-name-resolve 4. –skip-networking
Passwords by default are stored in hashed form in
database.But if the scrambled password is known the
hacker can still log in as the user.
Passwords can be stored in my.cnf file when
non-interactive access has to be done
Inbuilt functions for hashing: password,
Compatibility with Standards
What doesn’t MySQL have ?
Transactions – no provision for commit and
No nested sub-queries
Views are not supported
Foreign keys not used for referential integrity
What extra does MySQL have ?
Locking/Unlocking of tables
Atomicity of operations
Access of tables across tables
Several other features, discussed later…
More about Locks !
Locks help in maintaining integrity, atomicity
Read locks – enable you to only read from the
Write locks – enable you to read and write
exclusively. Other threads can’t access/update
currently locked tables
Write locks have higher priority than read locks
MySql Table Types
Creates a .frm file that holds the table and column definition.
Syntax for defining table type is .. :
CREATE TABLE test ( )
Categorization of types : Transaction safe type and Non
transaction safe type.
Transaction Safe table types allow rollbacks,restore changes if
update fails ,etc .
Non Transaction Safe table types are much faster ,use less
disk space as well as memory for updates.
Use B-Tree indexing to store the keys, string indexes
are compressed .
MyISAM itself supports three different table formats: a)
static (fixed length) b) Dynamic c) Compressed
Static : fastest ,secure and simplest format ,
used when there are no varchar, blob or text.
Dynamic : each record stores a header that contain its
Compressed : created using myisampack tool , they
are read only ,use very little space as each record is
ISAM is a deprecated version of MyISAM
A collection of identical MyISAM tables which are used
FOR eg :
CREATE TABLE t1 (a INT AUTO_INCREMENT
PRIMARY KEY, message CHAR(20));
CREATE TABLE t2 (a INT AUTO_INCREMENT
PRIMARY KEY, message CHAR(20)) ;
CREATE TABLE total (a INT NOT NULL, message
CHAR(20), KEY(a)) TYPE=MERGE UNION=(t1,t2)
• allowed : select ,insert and Operations update .
Heap tables and Berkley DB
Use hashed index and are stored in memory
Generally used for temporary tables .
•Berkley DB is used for making the tables
MySQL Language Reference
Syntax :: … OPTIMIZE TABLE tbl_name[,tbl_name]..
Used only for MyISAM tables
It performs the following functions :repairs the table if the table has
deleted rows,sorts the index,and the statistics are also made to
Syntax :: … CHECK
TABLE tbl_name[,tbl_name...] [TYPE = [QUICK | FAST | EXTEND
MySQL Language Reference
Checks a table for errors and updates the key
statistics of the table
BACKUP TABLE tbl_name[,tbl_name...] TO
This again works only for MyISAM
During analysis the table is locked with a read
MySQL Language Reference
REPAIR TABLE tbl_name[,tbl_name...] [TYPE = QUICK]
FLUSH flush_option [,flush_option]
Used to clear the internal cache of Mysql
It has various options like HOSTS,LOGS,PRIVELEDGES,
Replication in MySQL
One server is designated as the master, while the other
( or others) as slave(s)
Updates done only on master and binary logs made
The slave connects to the master, catches up on the
missed updates, and then starts receiving updates
immediately as they come to the master.
For robustness you have two systems and switch to
the backup if you have problems with the master.
The extra speed is achieved by sending a part of the
non-updating queries to the replica server.
How To (SLAVE)
• Upgrade both slave and master to 3.23.15 or higher.
• PUT THESE IN my.cnf of SLAVE
• server-id=< unique no>= 1 & <=2^32-1
• master-connect-retry !! (keep trying)
• Restart the slave(s)
How To (SLAVE) (contd)
• Take a snapshot of all the tables/databases on
• Use command LOAD TABLE <tblname>
FROM MASTER (3.23.23)+
HOW TO (MASTER)
log-bin , FLUSH MASTER , FLUSH SLAVE
When you start the slave thread will be created
Tables are not Locked
CHANGE MASTER TO master_def_list