MySQL

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MySQL

• Would You Like Some Transactions With That Table?

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Slides Are Available
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What Is MySQL?

• Most popular open source RDBMS
• Open source means 'free'
• Really? No cost at all?
• Widely used
• Sabre airline reservations
• Google
• LinkedIn
• What does Oracle DBA need to know?
• Many differences...

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Why Should I Care?

• I'm an Oracle DBA
• MySQL means nothing to me
• It isn't a 'real' RDBMS
• Why should I learn about MySQL?
• MySQL is being used by real businesses
• Can't hurt your employability
• Many jobs expect DBA to know multiple RDBMS
• Why not learn one that is widely used?
• And it's free you can download and install
  right now!

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Oracle DBA Perspective

• What will we look at?
• Installing
• Start/stop
• How database/tables stored
• Backups
• Transactions
• Storage engines

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My Message

• Compare MySQL to Oracle
• Not to be critical of MySQL
• Not to praise Oracle
• Make Oracle DBAs aware
• How much we assume about RDBMS
• Because Oracle does things a certain way
• MySQL is very different
• Assuming it is like Oracle can cause serious
  problems
• Does your business understand the differences?
• The cost of being 'free'?

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MySQL Versions

• MySQL Enterprise
• Have to buy support
• MySQL Community Edition
• The 'free' version
• MySQL Community Edition Preview Release
• Available for download
• Ready for prime time?
• Oracle doesn't offer 12g for trial download...

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MySQL Versions
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MySQL Where Did It Come From?

• Used to store web site logs
• Transactions
• What's that?
• If we lose some records
• So what?
• Supported by an individual
• Do your own thing
• Recovery
• Not to worry, plenty more web logs every day

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Some Differences MySQL/Oracle

• Oracle
• Database
• Schema
• a group of database objects
• Database user
• Maps to a database schema
• MySQL
• Server
• Databases
• Group of database objects
• Users don't map to database

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Some Differences MySQL/Oracle

• Storage engines
• Transaction support
• Performance
• Hot backup
• Binary logging and recovery
• Table locking
• Corruption
• Misc.

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Storage Engines

• MySQL gives you a choice
• Oracle, all transactional all the time (OATATT)
• MySQL storage engines
• MyISAM (IBM, Indexed Sequential Access Method)
• Very fast read
• InnoDB
• Transactional, like Oracle
• Separate software, owned by Oracle
• Many others
• See next chart

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Storage Engines
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InnoDB Storage Engine

• Imagine mixing
• MyISAM, InnoDB tables in a statement
• What does 'transactional' mean?
• What does recovery mean?

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CSV Storage Engine

• CSV storage engine
• Stores data in text files
• Using comma-separated format

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Blackhole Storage Engine

• My favorite

This is where we store all the data relating to
the Raiders and their 'Commitment to Excellence'
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Yeah, But...

• No problem
• I'll just make all the tables InnoDB
• Cool, but
• MySQL catalog (system?) tables are MyISAM
• Can't change them
• Table storage engine can be changed at any time
• Privileged users
• No one should do this, but...stuff happens
• Create table syntax
• Supports overriding default storage engine

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Transaction Support

• MyISAM
• Default table type
• Table type of system databases
• Does not support transactions
• Example
• Writing to MyISAM tables and server crashes
• Who know what was and wasn't written to tables
• No recovery

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Performance

• Many large MySQL servers in use
• Performance must be good
• or good enough for 'free'
• Optimizer
• Different storage engines
• How to optimize statement that has
• MyISAM tables
• InnoDB tables
• Does it support all storage engines you are using?

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Hot Backup

• MySQL does not have this
• Backup option 1
• Shutdown server, copy all files, startup server
• Backup option 2
• Lock all tables
• Dump all data to a dump file
• Dump file is set of SQL to recreate database
• Very slow to recover
• Backup option 3
• Buy hot backup software product
• Not free

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Binary Logging and Recovery

• MySQL
• Default, no logging
• You can configure binary logging
• Three formats
• Statement-based
• Row-based
• Mixed
• Binary log filenames have format
• binlog.000001, binlog.000002, etc.
• You must apply them in correct order

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MySQL Binary Logs

• MySQL does not have any way of knowing when
  replaying the binary logs which statements need
  to be executed and which are already committed.
• Oracle DBA doesn't worry about this
• Oracle checks and tells you which archived redo
  log is needed next
• Oracle won't allow archived redo logs to be
  applied out of order

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Binary Logging Formats
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Binary Log Issues
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Table Locking

• MyISAM storage engine
• Does not support row level locking
• Table locks
• Performance?
• InnoDB storage engine
• Supports row level locking

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Corruption

• Oracle
• I have rarely seen any cases
• But all tables support transactions
• MySQL
• What does it mean to rollback
• When different storage engines involved
• Some support transactions, some don't
• Some tables will be rolled back
• Others won't
• Is this corruption?

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MySQL Corruption Issues

• Good read
• Discusses corruption issues in MySQL engines
• I'm not saying this happens often
• But you need to be aware of these issues
• Another difference from Oracle
• Different storage engines, different corruption
  mechanisms
• http//www.mysqlperformanceblog.com/2006/07/30/mys
  ql-crash-recovery/

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MySQL Issues

• Misc
• Referential Integrity
• Some storage engines support
• Triggers
• Row-level, not statement-level
• Directload
• Not supported
• Parallel Query
• Not supported

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MySQL Issues

• White Paper
• Compares MySQL to PostgreSQL
• PostgreSQL, another open source RDBMS
• More like Oracle than MySQL
• Discusses issues with MySQL
• I'm not endorsing PostgreSQL
• But the whitepaper is very good
• Google
• PostgreSQL vs. MySQL A Comparison of Enterprise
  Suitability

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MySQL Table Storage

• MyISAM
• Each table has three files
• ltfilenamegt.frm Data dictonary information
• ltfilenamegt.MYD table data
• ltfilenamegt.MYI table indexes
• InnoDB
• Data and indexes in a tablespaces
• Made up of one or more datafiles
• Sound familiar?

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Documentation Online
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Documentation Online
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Documentation Online
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Talk Is Cheap

• A little less conversation
• A little more action
• Download and install MySQL to your laptop now
• Slides show the steps
• Windows
• You will have a fully functional MySQL server
• Start learning right now

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Install MySQL Windows

• Windows Vista
• 6.0 Service Pack 1
• Screenshots shown
• Windows XP
• Professional Version 5.1
• Same steps
• Very minor differences in what you see

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Downloads?
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Downloads?
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Enterprise Version
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Community Version
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Windows Downloads
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
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Windows Installation
Uncheck
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Windows Installation
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Windows Installation
Check
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Windows Installation
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Windows Installation
mysql
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Windows Installation
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Accessing MySQL Windows

• Click Start
• Programs
• MySQL
• MySQL Server 5.1
• MySQL Command Line Client
• Right-click
• Send to
• Desktop (Create Shortcut)
• Double-click desktop icon
• MySQL Command Line Client

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Accessing MySQL Windows
Shortcut created at installation
mysql
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mysql client utility

• Similar to SQLPlus

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Now What?

• Stop, start MySQL server
• What databases are available
• show databases
• Set default database
• use ltdbnamegt
• What tables are in the database
• show tables

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Windows Vista

• Stop/Start
• Services
• Start
• Settings
• Control Panel
• System and Maintenance
• Administrative Tools
• Services
• Scroll down to MySQL, highlight
• Upper left, options for Stop, Pause, Restart
• If MySQL is down, option to Start

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Windows XP

• Stop/Start
• Command line
• net stop mysql, net start mysql
• Services
• Start
• Control Panel
• Administrative Tools
• Services
• Services window
• Scroll down to MySQL, highlight
• Upper left, options for Stop, Pause, Restart
• If MySQL is down, option to Start

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System Databases

• INFORMATION_SCHEMA
• Catalog database
• MYSQL database
• User and privilege information
• TEST
• For you to play in...
• These databases are created at installation

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MySQL Server Configuration

• Controlled by 'option' file(s)
• Similar to Oracle pfile or spfile
• SHOW VARIABLES
• See current values
• Standard location(s)
• Search order
• One of the most common problems
• Persons don't know where these files are
• Make changes that don't take affect
• Can't find the file or files

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Option File(s)

• MySQL searches multiple locations
• Uses most recent value of each parameter
• How to know all files being scanned by MySQL?
• mysql help

Note dash dash help
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Option File
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Option File
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Option File
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Option File
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Option File
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MySQL Filesystem Layout

• From option file (my.ini)
• basedir
• Where software is stored
• datadir
• Where table data is stored

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MySQL basedir
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MySQL basedir/bin
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MySQL datadir
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MySQL Log Files

• General Query Log
• All client requests
• Binary Log
• Statements that modify data
• Slow Query Log
• Statements that take longer than 10 seconds
• Error Log
• Server messages

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MySQL Log Files

• Find log file locations

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Summary

• MySQL is 'free'
• May need other products to make it work for you
• Hot backup for example
• MySQL is widely used
• MySQL is very different from Oracle
• DBA tasks and issues will be different
• MySQL is not better or worse than Oracle
• Just very different

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The End?

• You now have a MySQL server installed
• No excuses
• Learn it, live it, love it
• Update your resume
• Next?
• Multiple MySQL servers on same machine
• Replication
• etc.