Which Database to Start With?

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When people ask me how to learn to use a database or how to write SQL queries, I tell them to pick a database system and immerse themselves in it. In fact that advice goes for a lot of software technologies: just immerse yourself in a language, as programming tutorials are easy to come by these days. On the other hand, when people ask me which database software to use, I tend to give pause. Most of the time, I recommend MySQL for beginners since it tends to be the most light-weight system to install and use, but I know it’s not often the easiest to understand. With the advent of new light-weight database editions of often heavier products, perhaps it’s time I reconsider the issue.

1. MySQL: Free, lightweight, and readily available

MySQL stands out as the easiest for users to start with, in part because most people can get access to a MySQL database without having to setup anything. Most, if not all, hosting companies that offer database support do so in the form of a MySQL database. The only disadvantage with hosting solutions is that users lose the ability to run local applications on the database, often relying on phpMyAdmin for all database changes. I recommend anyone serious about learning MySQL download and install it themselves, as there are plenty of installation platforms supported.

The good: Free. Easy to download and/or find an existing database to work with. Somewhat easy to install. Lots of free tools available. Good documentation.
The bad: If the installation or auto-configuration breaks, user is left spending hours diagnosing the problems. The MySQL GUI tools, while nice, have to be downloaded separately from the server. Limited support. Clustering and support of large transaction systems is not uncommon. Also, it can be buggy and unpredictable at times, as I’ve seen in practice.

2. Oracle: Heavy and Powerful

Oracle is one of the oldest database systems and stands out as a powerhouse among databases given its vast support for advanced clustering, memory management, and query optimization. If you need something robust, powerful, and able to support millions or billions of transactions a day, it’s the best there is. Oracle needs to be licensed for a production environment, although developers can download a free limited-use version which is good for building an application.

The good: Powerful. Can do some really cool things for those that appreciate it. Extremely scalable.
The bad: Often large and time-consuming installation. Least user friendly of all the database systems, although it’s gotten better over the last few years. Not free. Not a wide variety of tools, free or otherwise, to manipulate the database.

3. Microsoft SQL Server: Easy to use administration interface, often powerful

Microsoft SQL Server has matured greatly over the last 10 years into a decent rival of Oracle. I like MS SQL Server in that it hides a lot of the underlying configuration information from the user. On the other hand, I dislike MS SQL server in that it hides a lot of the underlying configuration information from the user. Double-edged sword, I know. Like Oracle, you need a license if you want to use it in a production environment.

The good: Easy to set up new databases and administer them. Best for those who have no idea how to administer a database. New express editions can be used for free.
The bad: Over-simplifies a lot for advanced users, making it harder to optimize. Not free. Developer edition has nominal cost, although it probably should be free.

Other Databases

This article is not meant to be the end-all for database software discussion, but a beginning guide of the big three database systems for those who are not well-versed in the area. To cover every possible database software, such as PostgreSQL or DB2, as well as countless others, would take a book or two. Most students starting out just need to find a single database and start ‘playing’ with it until they get the hang of it, rather than an exhaustive discussion of which database is best.

Non-standard Databases

Some of you may be more familiar with embedded databases such HSQLDB, SQLite, or Derby than the ones I have mentioned. Rarely do I see beginners using embedded databases, so perhaps I’ll write an article about such systems down the road. Also, I have not purposely not mentioned Microsoft Access as a learning database, simply because I don’t consider it standard database software, but rather a glorified Excel spreadsheet. Most of teaching someone how to use a regular database after using Access, is convincing them all databases are not like Access.

My favorite database? If I’m teaching or writing a relatively simple web-application, MySQL. If someone else is paying for the license and the application is large enough, Oracle.

memory profiling with jvisualvm

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I’ve been meaning to blog about jmap/jvisualvm for a while, but this JavaRanch question finally prompted me to do so.

My goal was to see where the memory was going in our JForum installation at JavaRanch. This was a one time thing, so I decided to see if I could do so without JProbe.   A colleague had already used Eclipse’s Memory Analyzer.  (Awesome tool by the way – it clues you right in to what it suspects are leaks.)  I decided to use jvisualvm.  Which was interesting.  While I was off exploring, someone else solved the problem and I put writing this up on the side.

I tried this locally on my machine to make sure I knew what to do before trying it on the production UNIX/Linux box.

How to run jvisualvm

  1. Get your process id:
    • Windows: JPS can be used to find your process id on windows.  At the DOS prompt, type “jps”.  My Tomcat process is called “bootstrap”  [I figured this out by stopping the process, running jps and then restarting the process running jps again.  I also had an unnamed process (Eclipse maybe?) and for jps itself.]  The JavaDoc says jps may not be supported in the future, but it works right now on Windows XP.
    • UNIX: You can simply use ps -ef | grep <whatever makes your process name identifiable>.  In my case, it was “ps -ef | grep coderanch”
  2. Run “jmap -dump:file=heap.bin.hprof 1234” [if your process was 1234].  Note this requires Java 6.
  3. Run “jvisualvm”
  4. file –> load –> choose hprof file from jmap
  5. Filter by classname – I used the package name net.jforum to narrow things down.  Which turned out to be a mistake as the memory leak was in Lucene.

or – Run” jhat -J-mx512m heap.bin.hprof”.  Thanks to this blog for helping with the jmap/jhat command.

[edited to fix typos]

how to test a local web application in blackberry simulator

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Surely there must already be a tutorial on this, but I didn’t see one.  I did see this information scattered amongst various places.  So here it is in one place.

My goal

Make JavaRanch’s JForum implementation more mobile friendly.  It’s not too bad on the iPhone because the iPhone has a better browser.  On the BlackBerry, the forums are much more difficult to use than they need to be.  As a result I plan to starting out by testing a mobile stylesheet with the BlackBerry simulator.  I found an online iPhone simulator.  After the mobile stylesheet looks on the BlackBerry simulator, I can upload it to a test server and try with the iPhone one online.

Note: I didn’t install the BlackBerry Eclipse plugin because I’m not doing BlackBerry development.  If you want the plugin, I did come across a very detailed tutorial.

Steps to bring up app in BlackBerry simulator

  1. From the BlackBerry download site, download both the simulator and the MDS package.  You need the later in order for the simulator to do internet.  If you have a slow connection, note that both are large downloads.  The simulator is 82 MB and the MDS is 45 MB.  (Note to RIM: if one is already running Tomcat, it would be nice to distribute this as a web app.  Smaller download, no need to change to port and less of a memory hog.)
  2. If you are already using port 8080 (such as to run your own Tomcat server.) Open the file “..\Research In Motion\BlackBerry Email and MDS Services Simulators 4.1.2\MDS\config\rimpublic.property” and change the “WebServer.listen.port” property from 8080 to 8081.  Thank you BlackBerry message board for this tip.
  3. Launch the MDS
  4. Launch the BlackBerry Simulator
  5. Launch your local Tomcat
  6. Test away.  Note that you must use your computer name rather than localhost.  (On windows this is the %COMPUTERNAME% property.)  Thanks to ASP forum for this tip.

Actually using the simulator

Some impressions of using the simulator:

  • It defaults to “100%” view.  100% of what?  No BlackBerry is that big!  On a 1024×768 resolution, the screen and keys don’t both fit on the screen.  I immediately switched to 50% view which is about an inch longer than an actual BlackBerry.
  • Luckily the keyboard works without having to click on the simulated device keyboard.
  • All the buttons have a real keyboard shortcut which you can see when mousing over the simulated key.  This helps with frequent operations.
  • To use the scroll wheel, you have to click and drag.  I would have expected mouse gestures to work here because they are more similar to what you do on the device.  Luckily there is a keyboard shortcut for this (hold F9 and use arrows to your heart’s content.)
  • It grays out if you don’t use it for a few minutes.  As does the real BlackBerry.  This is a bit annoying when testing though.
  • Luckily you can paste in from the real system clipboard – useful for testing URLS

Now that I’ve gotten used to the simulator, the site is just as hard to use on the simulator as it is on a real BlackBerry.  Perfect!  That means it suits my needs.

Problems/error messages I encountered

Since most people look for a “problem/solution”, I’m also listing the surprises in that format.  I know that’s what I was looking for!  I didn’t think I’d need a tutorial on setting up a simple piece of software.

  • BlackBerry simulator hangs when I try to access the internet – check you have installed the MDS, turned it on and you don’t have a port conflict
  • 8080 in use when starting MDS – see step #2 and change the port #
  • 403 error accessing localhost – see step #6 and use the computer name
  • Fledge.exe is using a lot of memory – this is the blackberry simulator itself; not much you can do here

The goal

I saw just how bad things look.  There’s a few more steps before actually making it look better – like getting rid of the table based layout.  But I did make progress with the tool support!