Improve the sqlite3 tutorial

[erlend-aasland]

Improve the tutorial using Diataxis as a guideline: https://diataxis.fr/tutorials/

The current tutorial is quite good, but it could make use of some improvements. The first that comes to mind, is:

• Provide a clear picture before we start the tutorial
• Some parts of the tutorial could make use clearer steps.
  • gh-95271: Extract placeholders howto from sqlite3 tutorial #95522
• Make the wording more to the point; avoid options and alternatives.
• Offer only minimum necessary explanation

Suggesting to split this up into multiple PRs, for the reviewers convenience.

[erlend-aasland]

cc. @CAM-Gerlach & @ezio-melotti #diataxis

[erlend-aasland]

Currently, the tutorial uses two different database examples (one stock exchange example, and a more recent programming language info example). We should aim to use just a single example database for the tutorial. That example database could also be used in other examples, sprinkled across the reference and in how-to's¹.

So, I'm not particularly fond of the stock exchange example; it works well, but it is ... maybe a little bit dull²? Would it be more fun for the aspiring Python SQLite database programmer if we expand on the programming languages example? Or perhaps something else?

Quoting Diátaxis, I think this touches upon the first item in this list; the example must be meaningful for the tutorial to be meaningful:

At the same time, the exercise you put your pupils through must be:

meaningful - the pupil needs to have a sense of achievement
successful - the pupil needs to be able to complete it
logical - the path that the pupil takes through it needs to make sense
usefully complete - the pupil must have an encounter with all of the actions, concepts and tools they need to become familiar with

Footnotes

1. It will probably not make sense to just use one grand example database for the whole sqlite3 docs; e.g., the type detection and the user-defined functions work best with stand-alone examples. ↩

2. No offence meant to the original author; it's just my personal opinion. ↩

[CAM-Gerlach]

So, I'm not particularly fond of the stock exchange example; it works well, but it is ... maybe a little bit dull2?

Maybe spice it up with some cryptocurrency? That's bound to be...exciting...these days... /s

As to the example, I'm really not sure. While being a relative subject matter n00b has been helpful in reviewing the docs from a more beginner perspective, I don't really have the required background to suggest something in this specific question, sorry.