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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Object Relation Mapping (ORM)

Another technical term? Yes - this one is a formal name for how you convert a database into Objects - applicable to any OO language (Perl, Python, PHP, Java ...)

Let's reduce it to basics.

* SQL Tables become object classes
* Table rows each become individual objects
* Individual columns become attributes.

OK - perhaps you've been doing it for years .... I know I have, though not so formalised. It's nice to have a buzzword now to impress people with! But there's more to it than that.

By writing code to formalise the conversion of data held in databases to objects, you can add a layer of abstraction and move the need to write SQL code within your application our to a separate module - very possibly a module that's already been written and placed on the CPAN or in the Cheeseshop or PEAR.

In Perl, there have been a number of ORM modules placed on the CPAN; the current "flavour of the month" is DBIx::Class. A year or two back, it was Class::DBI, which you'll still find in use on some legacy applications. Both DBIx::Class and Class::DBI rely on Tim Bunce's DBI module internally, so they can be used with the same wide variety of databases that DBI/DBD supports.




When you map a table onto a class, you'll note that your code repeats the definition of the column names in the Perl code (or Perl configuration file if you're being really good). But the programming axiom is "don't repeat anything" and if you're feeling REALLY clever, you can use DBIx::Class::Schema::Loader to pick it up from the database - as the cost of a little inefficiency in that the extra database enquiry is made every time you run your Perl. And THAT inefficiency can be prevented with dump_to_dir.
(written 2007-06-09, updated 2007-06-12)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Q908 - Object Orientation and General technical topics - Object Orientation: Design Patterns
  [485] North, Norther and Northest - PHP 5 Objects - (2005-11-04)
  [2322] Looking for a practical standards course - (2009-08-05)
  [2741] What is a factory? - (2010-04-26)
  [2977] What is a factory method and why use one? - Example in Ruby - (2010-09-30)
  [3608] Design Patterns - what are they? Why use them? - (2012-02-12)
  [3716] Learning C++ - a design pattern for your first class - (2012-05-02)
  [3810] Reading files, and using factories to create vectors of objects from the data in C++ - (2012-07-21)
  [3843] Caching Design Patterns - (2012-08-20)
  [4021] Spike solution, refactored and reusable, Python - Example - (2013-02-28)
  [4096] Perl design patterns example - (2013-05-20)
  [4098] Using object orientation for non-physical objects - (2013-05-22)
  [4325] Learning to program - what are algorithms and design patterns? - (2014-11-22)
  [4330] Java - factory method, encapsulation, hashmap example - (2014-11-27)
  [4356] Object factories in C++, Python, PHP and Perl - (2014-12-19)
  [4359] How to avoid too many recalculations within an object - (2014-12-21)
  [4377] Designing a base class and subclasses, and their extension, in C++ - (2015-01-01)
  [4396] Java Utility class - flexible replacement for array. Also cacheing in objects and multiple catch clauses example. - (2015-01-16)
  [4421] How healthy are the stars of stage and screen? - (2015-02-09)
  [4581] Thin application, thick objects - keep you main code simple. Example in Ruby - (2015-11-21)
  [4626] Singleton design pattern - examples and uses - (2016-01-20)
  [4663] Easy data to object mapping (csv and Python) - (2016-03-24)
  [4673] Separating detailed data code from the main application - Ruby example - (2016-05-16)

Q907 - Object Orientation and General technical topics - Object Orientation: Design Techniques
  [80] OO - real benefits - (2004-10-09)
  [236] Tapping in on resources - (2005-03-05)
  [507] Introduction to Object Oriented Programming - (2005-11-27)
  [534] Design - one name, one action - (2005-12-19)
  [656] Think about your design even if you don't use full UML - (2006-03-24)
  [747] The Fag Packet Design Methodology - (2006-06-06)
  [831] Comparison of Object Oriented Philosophy - Python, Java, C++, Perl - (2006-08-13)
  [836] Build on what you already have with OO - (2006-08-17)
  [1047] Maintainable code - some positive advice - (2007-01-21)
  [1217] What are factory and singleton classes? - (2007-06-04)
  [1435] Object Oriented Programming in Perl - Course - (2007-11-18)
  [1528] Object Oriented Tcl - (2008-02-02)
  [1538] Teaching Object Oriented Java with Students and Ice Cream - (2008-02-12)
  [2169] When should I use OO techniques? - (2009-05-11)
  [2170] Designing a heirarcy of classes - getting inheritance right - (2009-05-11)
  [2327] Planning! - (2009-08-08)
  [2380] Object Oriented programming - a practical design example - (2009-08-27)
  [2501] Simples - (2009-11-12)
  [2523] Plan your application before you start - (2009-12-02)
  [2717] The Multiple Inheritance Conundrum, interfaces and mixins - (2010-04-11)
  [2747] Containment, Associative Objects, Inheritance, packages and modules - (2010-04-30)
  [2785] The Light bulb moment when people see how Object Orientation works in real use - (2010-05-28)
  [2865] Relationships between Java classes - inheritance, packaging and others - (2010-07-10)
  [2878] Program for reliability and efficiency - do not duplicate, but rather share and re-use - (2010-07-19)
  [2889] Should Python classes each be in their own file? - (2010-07-27)
  [2953] Turning an exercise into the real thing with extreme programming - (2010-09-11)
  [3063] Comments in and on Perl - a case for extreme OO programming - (2010-11-21)
  [3085] Object Oriented Programming for Structured Programmers - conversion training - (2010-12-14)
  [3260] Ruby - a training example that puts many language elements together to demonstrate the whole - (2011-04-23)
  [3454] Your PHP website - how to factor and refactor to reduce growing pains - (2011-09-24)
  [3607] Designing your application - using UML techniques - (2012-02-11)
  [3760] Why you should use objects even for short data manipulation programs in Ruby - (2012-06-10)
  [3763] Spike solutions and refactoring - a Python example - (2012-06-13)
  [3798] When you should use Object Orientation even in a short program - Python example - (2012-07-06)
  [3844] Rooms ready for guests - each time, every time, thanks to good system design - (2012-08-20)
  [3878] From Structured to Object Oriented Programming. - (2012-10-02)
  [3887] Inheritance, Composition and Associated objects - when to use which - Python example - (2012-10-10)
  [3928] Storing your intermediate data - what format should you you choose? - (2012-11-20)
  [3978] Teaching OO - how to avoid lots of window switching early on - (2013-01-17)
  [4374] Test driven development, and class design, from first principles (using C++) - (2014-12-30)
  [4430] The spirit of Java - delegating to classes - (2015-02-18)
  [4449] Spike solution, refactoring into encapsulated object methods - good design practise - (2015-03-05)
  [4628] Associative objects - one object within another. - (2016-01-20)

P308 - Using SQL Databases from Perl
  [515] MySQL - an FAQ - (2005-12-03)
  [644] Using a MySQL database from Perl - (2006-03-13)
  [975] Answering ALL the delegate's Perl questions - (2006-12-09)
  [1885] Hiding a MySQL database behind a web page - (2008-11-15)
  [1904] Ruby, Perl, Linux, MySQL - some training notes - (2008-11-23)
  [2381] Checking the database connection manually - (2009-08-28)
  [2561] The future of MySQL - (2010-01-03)
  [3099] Perl - database access - DBD, DBI and DBIx modules - (2010-12-22)

G997 - Well House Consultants - Newsletter Lead Articles
  [1000] One Thousand Posts and still going strong - (2006-12-18)
  [1065] Graham Ellis - an Introduction - (2007-02-05)
  [1136] Buffering output - why it is done and issues raised in Tcl, Perl, Python and PHP - (2007-04-06)
  [1318] Well House Manor - feature comparison against the old place! - (2007-08-24)
  [1386] New software product for warmblooded programmers - (2007-10-10)
  [1488] New trainee laptop fleet for our Open Source courses - (2007-12-30)
  [1545] Letting new visitors know we provide training courses - (2008-02-19)
  [1600] Cambidge - Tcl, Expect and Perl courses - (2008-04-04)
  [1663] Python in an afternoon - a lecture for experienced programmers - (2008-06-01)
  [1754] Upgrade from PHP 4 to PHP 5 - the TRY issue - (2008-08-15)
  [1819] Calling base class constructors - (2008-10-03)
  [1912] Book now for 2009 - (2008-11-29)
  [2052] How was my web site compromised? - (2009-02-24)
  [2119] Make your business a DESTINATION business - (2009-04-05)
  [2253] Walks in and around Melksham, Wiltshire - (2009-06-21)
  [2370] C++, Python, and other training - do we use an IDE - (2009-08-21)
  [2425] Weekend and Christmas Promotion - Well House Manor Hotel, Melksham - (2009-09-26)
  [2538] Open Source Training Centre and Courses for 2010 - (2009-12-16)
  [2743] Public Open Source Training Courses running this summer and autumn in Melksham - (2010-04-27)
  [3202] Telling you something about us in just one line - (2011-03-15)


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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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