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Good Singapore Maths Students Would Likely Make Good Oracle DBAs (Problems) April 15, 2015

Posted by Richard Foote in Oracle Indexes.

An interesting mathematics based question from a Singapore high school exam has been doing the internet rounds in the past few days. Considering it’s aimed at high school students, it’s a tricky one and obviously designed to filter out the better students, in a country with a very good reputation for churning out mathematically gifted students.

I enjoy solving problems and this one took me a few minutes to work it out. However, at the end of the process, it occurred to me that I used a similar process to how I’ve often solved performance issues with Oracle databases. In fact, this question kinda reminded me of a performance issue that I had only just recently been asked by a customer to help resolve.

One needs to clearly understand the question being asked. One also needs to focus and understand the data at hand. Then use a process of elimination to both rule out and just as importantly rule in possible answers (or root causes to performance issues). Eventually, one can then narrow down and pinpoint things down to a specific solution (or set of answers).

So for example, the database is running exceptionally slow globally at certain times, why ?  So it looks like it’s because there are lots of cluster related waits at these times, why ? So it looks like it’s because writing to the redo logs is really slow at these times, why ? And so on and so on.

If you can work out the solution to this problem in a reasonably timely manner, then in all likelihood you have good problem solving skills and the makings of a good Oracle DBA. You just need to also like donuts and good whiskies🙂

I’ve reproduced the question here, changing the names to protect the innocent.

“Bowie and Ziggy just become friends with me, and they want to know when my birthday is. I give them 10 possible dates:

May 13   May 15   May 19

June 13   June 14

July 16   July 18

August 14   August 15   August 16

I then tell Bowie and Ziggy separately the month and the day of my birthday respectively.

Bowie: I don’t know when your birthday is, but I know Ziggy does not know too.

Ziggy: At first I don’t know when your birthday is, but now I know.

Bowie: Then I also know when your birthday is.

So when is my birthday ?”

Feel free to comment on what you think the answer is but please don’t give away how you might have worked it out. For those interested (or for those that don’t check out the solution on the web first🙂 ), I’ll explain how to get to the answer in a few days time.

Like I said, if you get it right, you should consider a career as an Oracle DBA !! And here’s a link to an excellent whisky: Sullivans Cove Whisky :)


1. Tony - April 15, 2015

July 16

Richard Foote - April 15, 2015

No comment (yet)

2. Chandra - April 15, 2015

I think it’s July 16🙂

Richard Foote - April 15, 2015

No comment (yet)

3. Nanda - April 15, 2015

June 13

Richard Foote - April 15, 2015

No comment (yet)

4. connormcdonald - April 15, 2015

So what’s the clustering factor between June and August ? or am I missing the point🙂

Richard Foote - April 15, 2015

Hi Connor

Hmmm, I see your point🙂 I’ll have to put in an indexing angle in here somehow ??

5. Martin Preiss - April 15, 2015

I miss here the hamster with the wooden leg from Jonathan Lewis’ mathematicians at the college reunion…

Richard Foote - April 15, 2015

Hi Martin

Sorry, no mathematicians allow here, regardless of their woodiness🙂

6. Atul Gupta (@atulgg) - April 15, 2015

July 16 most likely

7. Kev - April 15, 2015

June 13

8. David - April 15, 2015

As Tom Kyte would say..it depends. Answer June 13.

9. noname - April 15, 2015

May 19 or July 18.

noname - April 15, 2015

Sorry for incorrect interpretation. August 16

10. Margherita Guadagnin - April 16, 2015

I think it’s may 19

11. recurrentnull - April 16, 2015

june 13

12. taqvia - April 16, 2015

May 19th

13. RakeshDBA - April 16, 2015

July 16th

14. Anju Garg - April 16, 2015

July 16th

15. K.Vidhyasagar - April 17, 2015

It should be July 16th. (I did elimination and separation method)

16. maddurigayatri - April 17, 2015

I think the answer is 16 august(I used the method of elimination)

17. Niall McGee - April 17, 2015

July 16th, because

18. Will Morgan - April 18, 2015

No doubt – 0716*

*unless my coffee has failed me

Will Morgan - April 25, 2015

Wrong. Ouch. I didn’t see that Aug *16* … coffee failed me.

19. tonyC - April 18, 2015

Yup, definately June 13 – from a non-DBA, non-Mathamatician

20. Dani Schnider - April 18, 2015

June 13

21. urisnotaword - April 18, 2015

june 13

22. Florin - April 21, 2015

June 13th

23. Susant - April 21, 2015

Its July 18

24. Tony Scholefield - April 22, 2015

Good one. I eventually worked it out (I think – I will wait for the answer). FYI, I came to your blog via https://richardfoote.wordpress.com/2008/03/19/marcel-kratochvil-new-oracle-multimedia-blog-good-dba-bad-dba/ via Google when I was looking up Marcel. Your name came up at our AUSOUG-SA committee meeting yesterday in the context of successful / well attended presentations, which included your In Memory DB Presentation on 23-Jul-2014.

25. Singapore Maths Question Solution and Very Interesting Observation (The Trickster) | Richard Foote's Oracle Blog - April 23, 2015

[…] time to reveal the solution to the somewhat tricky Singapore maths exam question I […]

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