Someone has read my blog at last!

Had an email from my fellow student, Ian Macey, to say that he found this blog while googling. Ian, to my knowledge, you are the first and only person to read this blog! For a long while I had considered this to be a 'write only store' - a place where I just dump out an opinion or thought and that never gets read. Actually, the act of writing it is rather cathartic. I also have this picture in my mind of that lonely late -night radio DJ speaking into his microphone not knowing whether anyone is actually listening - but somehow enjoying the experience.

M359 - Constraint Checking

Just had an interesting, but inconclusive, FirstClass conversation regarding turning off Constraint Checking while performing a bulk load of data into a database. My view was that we have constraint checking for a very good reason: ensuring that the database remains consistent - because as soon as the data is inconsistent it then become unreliable, and if its unreliable then people will not use or trust it. So its pretty important!.

So the idea of turning off constraint checking during a bulk load sounds almost like suicide to me. But, it was pointed out that during a bulk load you are probably populating one table at a time, and if the table that a constraint depends upon is currently empty then the import will fail. So you HAVE to turn off constraint checking. A side effect is that it speeds up the import - well, to me that would be a side effect, but it has been suggested elsewhere that it might be considered to be a primary motive (!?).

But what really bothers me here, and so far no one has been able to convince me otherwise, is that if the data you are importing comes from another source over which you have no control, how do you know that the data is already consistent? And if it isn't consistent, and you have constraint checking turned off, you now have an inconsistent database! That can't be right.

One of the contributers to the discussion said that when constraint checking is turn back on after the import, error messages will be issued for any constraint that fails. I guess this is some help.

I'm still not convinced - there must be more to this.

M359 - Books

I have been reading this book by Chris Date. I have often found that reading the course books supplied by the university is not enough - not that I think that the university books are bad, they're not - its just that sometimes I need to see things written differently before they sink into my dense numbskull of a brain that I have.

Anyway, I like this book. There's no doubting that Date knows his field. And he worked alongside Ted Codd. Its also clear from the outset that Date's view of SQL is, how shall we say, not very favourable. In fact, on Page 2, he states "SQL /= The Relational Model" and goes on to say that if your only knowledge of the Relational Model comes from your knowledge of SQL then you don't know the Relational Model!. He couldn't really be any ore clear than that.

I like his writing style. Quite short and succinct. A little bit of humour - but just enough - not like one computing book I started to read, where the author dribbled on advising his readers to go and get a coffee while they thought about some stunning statement he had just made. He lost me as a reader almost immediately! Strangely enough, I can't remember the name of the book, or the author - thats the kind of impact it made upon me. Anyway, I digress.

But its early days - I'm still only on chapter 1. But my gut feeling right now is that I will last out until the end of the book and that it will help me with this course.

M359 - Studying Technique

I prevaricated earlier about which note taking technique to use. On previous courses I have taken copious hand-written notes and found that I very rarely ever went back to them, although the process of note taking seemed to help some of the information sink in.

This time I have forsaken the pen and paper approach and have been making notes in Microsft Word. Trouble is, I have realised that I am making even more notes than ever. This is going to make life harder than it need be I fear - so I have to find a way around this. I have also started to create my own glossary of terms (since one is not supplied as part of the course). For this I am using a good and trusty text editor. I can then use the sort command in the editor so that my glossary stays in alphbetical order. And in case you are wondering which text editor can sort lines, the anser is 'Kedit'. Kedit is based upon, and very similar to, Xedit that is used on IBM VM/CMS systems. I started using Xedit back in 1983 (when, for me, it replaced 'Edgar' its fore-runner). Xedit has always been a favourite of mine - very flexible, a decent language for writing macros (that language being REXX). So the editor is fully extendible, provides all kinds of sorting, manipulation and so on.

M359 - Making a Start

At last I am under way with M359. One week in and I have just finished chapter two of the first course book - which means that I am a week ahead of schedule. But there is to be no let up - I know that if I let it slip then it won't take long for me to be behind schedule, and catching up is always hard to do.
So, we have covered the usual sort of stuff for the beginning of a course - what is data, what is information, what happened with data historically - Mesopotamian tablets, 15th Century Tally Sticks, 16th Century Parish Registers. How computerised databases came about, why was there a need, what types, how they have evolved.
Now we have getting down to the three-schema model, seperation of concerns, and all that stuff.
First TMA is also available and due to be started yesterday but covers subject matter that, officially, we don't cover on the course for another two weeks!

Keep it comming.

M359 - Some progress

Still worried. I have access to the M359 Course Website as of yesterday, and to the M359 First Class Conference as from this morning - but still no sign of any course materials. That's nine days now since they were dispatched. I wonder which company they use for their deliveries.

In the meantime, I am puzzled as to why there is only one conference for M359. With other OU courses that I have studied there have always been several conferences - a general social chit-chat conference, a general course conference, a tutor-group conference, and then a seperate conference for each TMA. I hope that these other conferences will start to appear soon - the OU must have know that M359 was starting in February!

M359 - Still nothing

Well, two days to go until the course officially starts and still no sign of any course materials, access to the course website, or to the Course Conference on First Class. So, being slightly worried about this I telephoned the OU Computing Help Desk and explained the situation. A few checks by the man on the phone and his response was 'oh yes, you do seem to have some services missing' (which is fine, but I had already guessed that bit!). He said he will forward the request on to the appropriate team at the OU so that they can give me access. The good (I hope) news is that their records show that the course materials where dispatched by land-snail on 24th January.

So.....I'll just keep waiting and hoping.

Also today, I had an letter from the course Tutor, Dorothy Carrier (or, Dot Carrier, as she prefers to be called), just welcoming us all to the course and giving us some of her background. A useful letter I thought. I have responded by email and relayed some of my background to her.