The latest happenings at the Baltimore Washington Java Meetup

I just sent out an email to the illustrious members of my Java User Group (JUG), aka the Baltimore Washington Java Meetup.  The text is below.  All those interested in Java technology are invited and welcome!

Well well well!  What an AMAZING night we had for our November meetup!  I’ve been remiss to have not sent this sooner – things have been busy busy busy in Steve world – but you should know that November 10th was an amazing night.  We had about a billion people there – well, ok, perhaps it wasn’t a billion, but in all seriousness we maxed out the room – and it was all to hear the most excellent presentation by our very own rock star, Markus Dale, and his Overview of Amazon Web Services (AWS) and its Java API.  On hand were many illustrious members of our meetup, plus some additional celebrities, namely AWS’s Walt Whitecotton, John Peterson, and John Quarentello, who brought plenty of Amazon swag with them as giveaways and door prizes.

Speaking of the door prizes … the questions were:

1) Do you use (circle all that apply) (a) Ant, (b)Maven, (c)Jenkins, (d) Hudson?

Every answer was selected and there was a write-in or two for Gradle. But the hands-down leading choice was Maven.

This question was posed at JavaOne to a room of about 200 developers.  By a show of hands, about half used Jenkins, half Maven, and two people use Ant.

2) An annotation can be extended: (a) True (b) False

The correct answer is false! Now … should they be extendable?  Well that’s a different question altogether.  But in the meantime –

Congratulations to all the winners, especially Peter Stamboulis who won the 1st place price, a gift card for Amazon Web Services!

Most of all, a great big thank you and “bravo!” to Markus Dale, who clearly knows his stuff and did a fantastic edge-of-your-seat presentation on one of the hottest cutting-edge topics in the IT field today.

SO … our next meetup is … TONIGHT!  As we’ve been saying this fall, our December meetup would be non-standard, not a technical session, and that’s definitely the case this evening! We are simply meeting for dinner at a great restaurant in Columbia – pay your own way – click here for details.

In 2016 we’ll resume with technical sessions and already have a few in the works:  Lambdas, data streams, new features in Java 9, our own participation in the Adopt-A-JSR effort, and more!

But for tonight, we’re having a fun holiday dinner (pay your own way!), and everyone is invited!

See you tonight!

– Steve

My SQL Expert Book and Practice Exams

I recently read in an online forum the online bonus exam for my book, OCA Oracle Database SQL Certified Expert Exam Guide (Exam 1Z0-047), is “no longer available” at the Oracle Press website.  I’m inquiring into this to determine if its true, and if so, to see if we can get it restored.  If you’ve had a similar experience, please email me to let me know.

In the meantime:

  • I have created additional practice exams here:  They are available at no charge, and only require that you registered an email address so you can take the exams in multiple login sessions if you wish.
  • I am currently working on a revision to my book, to upgrade it for Oracle 12c.  Lots of new feature we’re adding, and I’ll blog about those soon.  The second edition will be completed in early 2016.

In the meantime, if you’re looking for a practice exam, please check out!

Java, SQL, and the ORM Mismatch

I just can’t take it any more.

There is an incorrect perception floating around out there in Java world about the issue of mapping Java classes to SQL tables.  This issue falls within a larger topic often referred to as the object-relational mapping (ORM) mismatch.  This “mismatch” is based on the fact that Java is object-oriented, and SQL is not, so using Java classes to represent SQL tables involves some issues, and requires some clever work.  That is true.  But it’s led to a major misperception about SQL being supposedly “defective”.  It is not, but this notion has crept its way into two books I’ve read lately, books by otherwise very smart people, published by major cutting edge IT book publishers.

(For the record, no, neither publisher in question is my own publisher, the incomparable McGraw-Hill Education and their awesome imprint with Oracle Corporation, Oracle Press.)

I’m not going to verbally quote either work, but the idea goes like this:

  • To support persistence (storing data), you map a Java class (ex., “Customer”) to a corresponding SQL table (ex., “CUSTOMERS”)
  • When creating two Java classes, it’s possible to design them with a many-to-many relationship to each other
  • SQL doesn’t support the creation of tables with many-to-many relationships
  • Therefore SQL is defective.

Uh – no.

Folks, the presence of a many-to-many relationship in your data model is a sign that you aren’t finished with your data model.

This isn’t a Java thing, or a SQL thing, it’s a real world thing.

It’s possible to build a defective data model in Java.  You can do a lot of stupid stuff in Java.  You can also build bad data models in SQL, and technically you actually can create a many-to-many in SQL, but it won’t work.  That’s a good thing.  I’ll explain shortly with an example.

But first, a word about the classic mismatch.


The authors of these two books I’ve read are Java developers first and foremost.  I get that, and I know where they’re coming from.  I’m a Java developer myself, and have been since Java was first introduced into the Oracle database as an alternative to PL/SQL, which I also love – so much that my first book was the official Oracle Press certification exam guide OCP Developer PL/SQL Program Units Exam Guide.

But about the time that book hit the shelves, I began working with Java, which had become available as an in-database alternative to PL/SQL.  I soon thereafter began teaching Java.  In fact, this is me with then-CEO of Sun Microsystems, on the first day I launched my first ever course in Java:

Scott McNealy, Steve O'Hearn, at the National Press Club

That was taken at the National Press Club.  McNealy was hysterically funny that day and a great guy. He’s responsible for, and oversaw, a lot of great developments in Silicon valley that reverberate to this day – like Java.

And back at that time, the first question about Java was – how do we get Java and SQL to interact?  That, after all, was Oracle’s whole point of embedding Java in the database.

Java has come a long, long way since then, and all for the better.  There is a well established and growing library of packages and tools for implementing various interactions between Java and SQL.  And at the heart of them all is often the same issue:

Java is object oriented, and SQL isn’t.

True.  So what?  Newcomers to Java act like this is some kind of ultimate nightmare scenario, a sign that SQL is out of sync with the world.  Nonsense.  SQL isn’t inherently object-oriented, but neither is your file system.  And yet Java interacts with files just fine.  Now granted, the idea behind SQL is more sophisticated than file systems.  But on the other hand, SQL isn’t in the same category as a third-generation language (3GL) like Java, SQL is a fourth generation language (4GL). It might not support object-oriented dynamics, but neither does it clash with them.  This is demonstrably obvious – otherwise we wouldn’t have JDBC, the Java Persistence API (JPA), and Hibernate.  So the two can and do work together, and effectively.  But it takes a bit of work; SQL doesn’t necessarily provide built-in support for all object-oriented concepts, such as inheritance. (Caveat: Inheritance actually can be supported in data modeling – see this article – and there’s a way to do it within SQL itself, sort of, but as to whether it’s helpful or not, that’s a different story, and perhaps the topic of a future blog post.  Or book.  Hm …. )

Frankly, when I hear about the “mismatch” between Java and SQL, I think of the issue of transactions, that’s the only real issue to me. The object life cycle and nature of Java is such that it introduces challenges in the way persistence to the database is best done in a multi-user/multi-threaded environment.

But let’s get back to topic and dispel this “SQL is defective” myth.


Data modeling is the act of representing real world business processes through diagrams of the things (“entities”) that comprise a real world process, and the relationships (or “associations”) among those entities.  The most obvious entities are easy to identify – customers, products, office buildings, vendors, cars, etc.  But the more abstract entities are not always so obvious – work schedules, change orders, reservations, that sort of thing.  This is where the importance of understanding many-to-many relationships can be very helpful.


I’m going to use an example taken from the airline industry, as I’ve been meeting lately with Lisa Ray, a lifelong aviation data expert closely involved with a series of legacy migrations in that area. (And for the record, she fully gets this.)

Let’s start with two obvious entities:

  • Planes – as in “individual planes”, not just types of planes.
  • Pilots – individual people.

Every one plane might be flown by more than one pilot.  Every one pilot will be qualified to fly more than one plane.  Sounds like a many-to-many relationship, right?  And as you might know, an entity-relationship diagram illustrates the “many” side of a relationship with the classic crow’s-feet line:

ERD Diagram A

So that’s our initial logical diagram for these two entities.

Now folks, this blog post is not going to be a complete tutorial on how to perform data modeling, but we will explore one key aspect of modeling: whenever you encounter a many-to-many relationship, you ALWAYS transform it using the following steps:

  • Add a third entity in between – “Entity_3” in our diagram below.
  • Create foreign keys within the new entity for the primary keys of the existing entities – in this case, PLANE_ID as a foreign key to the PLANES entity’s PLANE_ID primary key, and PILOT_ID as a foreign key to the PILOTS entity’s PILOT_ID primary key.
  • Establish “one-to-many” relationships between the new entity and the existing entities, using the “single-line” to indicate the “1” side, and the “crow’s foot” to indicate “many” side of the relationship.

Like this:

ERD Diagram B

The reason we do that is simple:  the presence of a many-to-many relationship is a clear indicator that something else goes in between the two entities.  The question is not “if” something belongs there.  Something does belong there.  The only question is – what exactly is it?

In our example, it’s going to be something like a “roster”, or a “schedule”, or “flight assignments”, or “rentals”:

ERD Diagram C
Call it what you will, but something goes in between and it must be included in your data model.  That new entity will have its own attributes.  Perhaps:

  • A start and end date to the time of assignment
  • A name of a key staff member authorized to approve the assignment

Who knows what might be there? But something is there, and the presence of the many-to-many relationship is your clue to its existence.

That third entity is often a bit more abstract.  You can see pilots and planes, but a “flight assignment” isn’t necessarily as obvious.  But it’s an important entity in the data model nonetheless.

One more point:  this third entity isn’t some necessary crutch to get around a “SQL defect”. I can’t believe what I’ve read in certain Java books that suggest such a thing.  No.  This third entity is a real world “thing” that definitely exists in order to enable the relationship with the real world, and it’s up to you to identify it. Whether you figure it out or not, it exists nonetheless.

The rule is simple: no complete data model exists with any “many-to-many” relationships.  If such are present, you aren’t done modeling yet.

So now that you understand this, imagine reading a Java manual in which someone explains that SQL is “defective” because it “doesn’t support many-to-many relationships”.


Now you know!

O’Hearn is the Java leader of the only officially recognized JUG for the DC metro area.  He is also the author of the first-ever expert-level certification exam guide from Oracle Press, titled OCA Oracle Database SQL Certified Expert Exam Guide (Exam 1Z0-047).  The 2nd edition of his SQL Expert book, revised for Oracle 12c, is due out in 2016.

Number one again in time for OOW 2014

A great thank you to my readers!  See below!

SQL Expert book at number one again on Amazon's Oracle booklist

I just grabbed the above image from the Amazon website earlier tonight, September 24, 2014, at 11:52 p.m.

It shows that my book – OCA Oracle Database SQL Certified Expert Exam Guide (Exam 1Z0-047) – is number one again at’s Oracle category, less than one week prior to the Oracle Open World / JavaOne 2014 conference in Silicon Valley.

A hearty thank you to all my readers on behalf of me and the writing and editorial team at McGraw-Hill and Oracle Press!  Thank you thank you!

Congratulations to jaramill “gjaram”!

A hearty congratulations to jaramill “gjaram” and a big thank you as well for the excellent review he posted of my SQL Expert book at  He wrote:

“This is my review 3 months after I bought the book but just 2 days after taking the exam……and PASSING it on the first try!”

So welcome jaramill to the world of certified SQL experts! And thank you for the very nice review.

If you wish to see jaramill’s complete review click here, it’s titled “Worthwhile guide to help you for the exam” and gives my book five out of five stars.

“Mind blowing book”

I’m sending out a huge thank you to Gobikrishnan Srinivasan for this great comment about my book that he posted online:

“I did my certification on last saturday being a sql expert u r given a class A seat and my suggestion is go for steve o hearn books its simply mind blowing book i learnt a lot from it it helped me to pass the exam”1

You can see this comment for yourself on LinkedIn, in a discussion among the elite members of the Oracle Database SQL Certified Experts group.  Gobikrishnan is a member of that group and lists himself as a Compliance Analyst at IBM.

The book he’s talking about of course is OCA Oracle Database SQL Certified Expert Exam Guide (Exam 1Z0-047).

Thank you Gobikrishnan for the great endorsement!

SQL Expert is number one again

SQL Expert book at number one on Amazon's Orace booklist

Some friends have drawn my attention to the fact that my 2009 book OCA Oracle Database SQL Certified Expert Exam Guide (Exam 1Z0-047) has been back at number one in Amazon’s “Oracle” books list.

I’ve observed that Amazon’s best-seller lists appear to be updated as often as hourly.  So it might be at number one as I type this, but elsewhere – such as 4th or 7th – later in the day.  This latest book of mine has been bouncing around in the top 10 of all Oracle books for a few months now.  Every now and then it will show up as number one, perhaps about once every few days in my observation.  Now – if I had privileges to query Amazon’s database, I could produce an accurate and comprehensive report.  If you’re a reader of my book, you could create such a query too!

On the book’s main page, Amazon displays a “Best Seller!” flag when it hits number one, with a link to the list.

I’m sure the interest in the book is largely driven by the exam itself, of course, which is a fantastic professional credential for anyone to get.  When you can add a blurb to your resume with the keywords “Oracle” and “expert” together, you’re doing treat.  That being said, I’ve also received plenty of email from readers who are just honing their skills and filling in gaps in their knowledge, with or without plans to take the exam.  The book is uniquely useful for that as well.

So – a huge “thank you” to all my readers!  You’re the reason this is all happening, and I thank you.

New app reads your mind

A new application for the cutting edge Google Glass platform will read your mind.  The app can sense when your brain waves indicate you’re focusing on an image.  When you focus, the app will snap a picture of whatever you’re looking at through the eye glasses and upload the image to Twitter.

It’s called MindRDR and TechCrunch wrote about it here.  To read your brainwaves, it uses a third party device called the Neurosky EEG biosensor, which integrates with your eye glasses.

What do you think?  Would you use it?

Conference in Williamsburg, Sqoop, and Big Data Connectors

Yesterday  – April 24, 2014 – I had the privilege of presenting at the Virginia Oracle User Group (VOUG) annual Oracle Conference on the James, or OCOJ for short.  The “James” is the James River right there in Williamsburg, Virginia.  I promised my audience I would publish the Power Point slides, so here they are:

Yesterday could not have been a more glorious day. The Doubletree Hotel in Williamsburg is really a conference center, with a variety of beautiful meeting rooms and great skylights and large glass walls.  The room in which I presented was unusual in that it had one door that led directly outside.  The hotel propped it open and the beautiful air flowed it, it was remarkably refreshing.  I particularly enjoyed it, given the many snow days we’ve had this past winter and even into the spring.  The air was fresh and the temperatures just perfect, what a great day.

I was definitely in with some illustrious company – other presenters throughout the day included Mary Gable, David Mann, Craig Shallahammer, Greg Mays, Scott Poteet, Bill Myers, and Oracle’s own Bob Bunting as well as Robert Freeman.  The legendary Tom Kyte (of Ask Tom fame) was the keynote speaker.  Brilliant talent was on display everywhere.

For more information about VOUG, visit their website here:

Here’s a copy of the full conference agenda:  VOUG OCOJ Conference Agenda.

Thanks to one of my great audience members who took the photo.  And a huge thanks to Linda Hoover for making the entire event possible – thank you Linda!