Editor's Letters: Tips and Thoughts from Readers
“Computer and Internet tips, plus comments on the articles and columns.”
by ComputorEdge Staff

Warning for Simple Table Creation

[Regarding the October 23 Rob, The ComputorTutor Does VB.Net 2010 column:]

As a long-time Oracle DBA, let me just pass along a warning about using the techniques shown in simple examples in "real" code. There have been numerous discussions in the database design world about using ID (autonumber in Access) fields in tables.

Since an autonumber guarantees a unique primary key (PK) each time, there is a possibility of creating duplicate Person records. If my code doesn't check for duplicate entries, I could add duplicate records for Jane Doe a zillion times—and all zillion records will appear in the database. Sometimes, it is legitimate to have more than one person named Jane Doe. Other times it is a mistake created by an end user who clicked the Add button too many times.

With just the first/last name as the only columns in the table, it would be virtually impossible for anyone to determine whether the database contains duplicate records or multiple people with the same name. In the real world, developers should always provide enough fields in a table for someone to detect the duplicates or same names.

I realize your example is just to teach a principle, but developers need to be aware of the repercussions of extrapolating the simple example into a full-fledged database app. As a DBA, I cannot tell you how many times I have been asked to delete duplicate records from a database because the ID field allowed someone to add those duplicates. It's up to the developer to ask the user when they click Add and some of the fields (other than the ID) match other records.

Just mentioning this as a caution you might include in your discussion.

-Roger Crowley, Poway, CA

Free MP3 Resources

[Regarding Dawn Clement's October 2 article, "Finding Free (Legal) MP3 Downloads":]

Nice article. It is worth pointing out that there are hundreds of Net labels that are out there, putting out all sorts of music that is free for download. A Google search will certainly set any reader off in the right direction!

Best,

-Dean, Leiden, Netherlands
Rack & Ruin records

Digital Cameras

[Regarding the October 23 Editors Letters: Tips and Thoughts from Readers column:]

To Kathee from Dallas:

Our children bought a Nikon D70s (used) for my last birthday. [It has] a 55mm to 200 mm zoom. I bought an 18mm to 105mm that I use 99 percent of the time. It's 6 MP and has loads of bells and whistles. Will take up to a 4 meg CF mem card. You could spend a lifetime learning it all.

-William B. Tiep, Toledo

As a veteran Canon and Nikon film camera user, I would advise Kathee to be sure to look long and hard at the gamut of offerings from electronic companies.

-Cicero Walker, Colorado Springs, CO

Destroying Hard Drive Data

[Regarding the October 23 ComputorQuick Tips column:]

The physical media must be destroyed. Period! Destroying just the PCB or letting in contaminated air still allows the data to be recovered. I used to make usable drives by replacing the PCBs in the old 30MB drives.

The federal government TLA agencies used to have a special DD-19 and DD-29 case designed with a 45 cal pistol welded to the top pointing at the platters inside. That was how the security was maintained at our federal agencies that used Cray supercomputers.

(No, I won't divulge who were our purchasers.)

-Art, Evergreen

With regards to his [Pete's] Method 1—Breaking the green circuit board does nothing to the data stored on the disks themselves, and replacing that broken board with a good one would most likely allow sectors to be read once again. This is not to suggest that his method won't work—pounding on the drive anywhere with a hammer will pretty much screw up the ability of the disks to spin under the heads. He's just completely wrong about the cause and effect.

Better advice: If you have a hammer, pound on the aluminum cover side and crush the disks directly, making it impossible to retrieve any data bits.

With regards to his Method 2—There will never be a "whoosh" as the "vacuum seal" is broken. Disk drives don't operate in a vacuum. In fact, a vacuum would make them fail because they depend on a cushion of air to prevent the read head from making actual physical contact with the disk. And platters are never made of glass, but instead are aluminum with thin films of magnetic material sputtered on them.

-Jim Luschen

Jim,

You are correct when you say that destroying the circuit board of the drive does nothing to the stored data. It was not my intent to infer that Method 1 was designed to destroy the data. In fact I did point out that data could be retrieved, but only at the high cost of using professional data-recovery services. I would use Method 1 when there is no sensitive data on the drive, but you really just don't want the drive to be used again.

You are also right that there is not a vacuum seal on the hard drive. I have done some further research on this and have found, rather, that hard drives are kept at an equilibrium air pressure. The sound you hear when you open the drive is possibly air passing through that small hole on the back of the drive. Thank you for pointing this out. I should have looked further into hard drive construction before I said that.

Here is a nice article that explains the inner workings of hard drives and also provides very detailed screenshots. They do not show how to dismantle a hard drive, but using their screenshots and the instructions in these ComputorQuick Tips, the average user can safely and securely dispose of their old hard drives with little cost, which is the point of my tips this week.

You are correct that traditionally, hard drives have been manufactured with aluminum made platters; however, many manufacturers have gone to newer materials using glass and glass composites like ceramics. These are then coated with a thin magnetic film. This newer material is supposed to allow for the more advanced designs and higher demands of the faster hard drives. The traditional aluminum material was not designed for today's faster drives and are too uneven. They don't allow for the uniformity that the newer materials can provide. I did look this up here and here.

I recommend extreme caution when removing the platters. Always wear eye protection, as the platters can shatter and the material can fly into your eyes.

-Pete Choppin

Windows Tips and Tricks: A Windows 7 Review

Opening the shipping carton.

I have just purchased my first Win 7 computer and am getting ready to set it up. It is an economy model that will replace the older of my two XP/Ubuntu partitioned computers in my office. I may add Ubuntu to the new computer as a virtual machine application. Your articles in this issue are very encouraging and informative. I successfully avoided Vista and have never even tried it out, and am now a bit apprehensive about the whole thing.

Thanks for the help!

-Cicero Walker, Colorado Springs, CO

Mr. Dunning,

Read your article on Win 7 in the 10/23 issue and was startled to read that 7 had no e-mail client. I currently employ several XP Pro computers in a network, all of which depend on Outlook Express. There are hundreds of addresses involved, with collateral info on most, plus numerous e-mail folders with important msgs. All of this is backed up, but it would be a monumental task to transfer it all to another e-mail client. It's hard to believe MS has no path for OE. If this is true, it looks like any new hardware we buy will require XP. I think MS grossly underestimates the size of the installed XP base. Wonder how IT shops based on XP in the big corporations will be handling this. My employer won't even let us go to IE8 because it doesn't support current operations. Any comment?

Best,

-Joe Silverman

There is an e-mail client, Windows Live Mail, available from Microsoft as a free download that will import all of the Outlook Express messages and contacts (contacts will need to be exported into another file first). I address the topic of e-mail clients and Win 7 in next Friday's column.

Regardless of which way you go, you will still need to move all of your messages and contacts. Windows Live Mail does have an Internet capability that could make it easier to share contact information.

-Jack Dunning, ComputorEdge