ANSI Joins and Uppercase Keywords – making PL/SQL look less like COBOL

The month-long festival of football has finally come to an end.
A tournament that was supposed to be about “No 10s” and the coronation of the host nation has lived up to expectations. Ironically, by defying them.

Where to start ? Well, it seems that goalkeepers had something to say about just who the star players were going to be.
Ochoa, Navas and Neuer were all outstanding, not to mention Tim Howard. I wonder if he could save me money on my car insurance ?
Those number 10s were also in evidence. However, in the end, it wasn’t Neymar, Messi, or even Mueller who shone brightest in the firmament. That honour belonged to one James Rodriguez, scorer of the best goal, winner of the Golden Boot, and inspiration to a thrilling Columbia side that were a bit unlucky to lose out to Brazil in a gripping Quarter Final.
Now, usually a World Cup finals will throw up the odd one-sided game. One of the smaller teams will end up on the wrong end of a good thrashing.
This tournament was no exception…apart from the fact that it was the holders, Spain, who were on the wrong-end of a 5-1 defeat by the Netherlands.
Then things got really surreal.
Brazil were taken apart by a team wearing a kit that bore more than a passing resemblence to the Queens Park Rangers away strip.
The popular terrace chant “It’s just like watching Brazil” may well require a re-think after Germany’s 7-1 win.
So, Germany (disguised as QPR) advanced to the final to play a side managed by a former Sheffield United winger.
Eventually, German style and attacking verve triumphed.
Through the course of the tournament, O Jogo Bonito seems to have metamorphosed into Das Schöne Spiel.
The stylish Germans are what provide the tenuous link to this post. I have once again been reviewing my SQL and PL/SQL coding style.
What follows is a review of some of the coding conventions I (and I’m sure, many others) have used since time immemorial with a view to presenting PL/SQL in all it’s glory – a mature, powerful, yet modern language rather than something that looks like a legacy from the pre-history of computing.
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Tracing for fun and (tk)profit

If you ever wanted proof that time is relative, just consider The Good Old Days.
Depending on your age, nationality, personal preferences etc, that time could be when rationing finally ended; or when Trevor Brooking won the Cup for West Ham with a “bullet” header; or possibly when Joe Carter hit a three-run homer to seal back-to-back World Series for the Blue Jays.
Alternatively, it could be when you were able to get on to the database server and use tkprof to analyse those tricky database performance issues.

In these days of siloed IT Departments, Oracle trace files, nevermind the tkprof utility are out of the reach of many developers.
The database server itself is the preserve of Unix Admins and DBAs, groups which, with good reason, are a bit reluctant to allow anyone else access to the Server at the OS level.

Which is a pity. Sometimes there is just no substitute for getting into the nitty gritty of exactly what is happening inside a given session.

For those of you who miss The Good Old Days of tkprof, what follows is an exploration of how to access both trace files and even the tkprof utility itself without leaving the comfort of your database.
I’ll go through a quick recap of :

  • how to generate a trace file for a session
  • using tkprof to make sense of it all

Then, coming bang up to date :

  • viewing a trace file using an external table – and why you might want to
  • Using a preprocessor to generate tkprof output
  • implementing a multi-user solution for tkprof

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Oracle External Table Pre-processing – Soccer Super-Powers and Trojan Horses

The end of the European Football season is coming into view.
In some leagues the battle for the title, or against relegation is reaching a peak of intensity.
Nails are being bitten throughout the continent…unless you are a fan of one of those teams who are running away with their League – Bayern Munich, Juventus, Celtic…Luton Town.
In their fifth season since relegation from the Football League to the Conference, Luton are sitting pretty in the sole automatic promotion place.
Simon is desparately attempting to balance his “lucky” Christmas-cracker moustache until promotion is mathematically certain. Personally, I think that this is taking the concept of keeping a stiff upper-lip to extremes.

"I'll shave it off when we're definitely up !"

“I’ll shave it off when we’re definitely up !”

With the aid of a recent Conference League Table, I’m going to explore the Preprocessor feature of External Tables.
We’ll start with a simple example of how data in an External Table can be processed via a shell script at runtime before the results are then presented to the database user.
We’ll then demonstrate that there are exceptions to the rule that “Simple is Best” by driving a coach and Trojan Horses through the security hole we’ve just opened up.
Finally, in desperation, we’ll have a read of the manual and implement a more secure version of our application.

So, without further ado… Continue reading

PL/SQL Associative Arrays and why too much Rugby is bad for you

Once upon a time, working on an IT project in a large organisation meant reams of documentation, tangles of red-tape, and then burning the candle at both ends to get everything finished on time.
Then, someone discovered this Agile thing that dispensed with all of that.
The upshot ? Well, the documentation has been reduced ( although the red-tape is still problematic).
Many large organisations now adopt an approach that is almost – but not completely – unlike SCRUM.
It is at the business end of such a project I now find myself…burning the candle at both ends.
To pile on the excitement, Milton Keynes’ own Welsh enclave has become increasingly voiciferous in recent days.
The only SCRUM Deb is interested in is that of the Welsh Rugby Team grinding remorselessly over English bodies come Sunday.
She keeps giving me oh-so-subtle reminders of the result of last year’s game, such as when picking lottery numbers :
“Hmmm, three is supposed to be lucky…but not if your English. How about THIRTY !”
“But you’re married to an Englishman”, I pointed out during one of her more nationalistic moments.
“Which makes him half Welsh !”, came the retort.
At this point, I decided that discretion was the better part of logic and let the matter drop.
As a result of all this frenzied activity and feverish atmosphere, sometimes I’ve not been quite at the top of my game.
One particularly embarassing mishap occured late one evening and involved PL/SQL Tables – or Associative Arrays as they’re called these days – and the dreaded ORA-06531: Reference to uninitialized collection.

This particular post therefore, is mainly a reminder to myself of how to initialize and (just as importantly) clear down a Collection to prevent mysterious missing or, just as problematic, additional, records ( as well as less mysterious runtime errors). Continue reading