Databases: Intro, Relational and XML (Hierarchical)

First day wasn’t so bad. I watched about 40 minutes of video at 1.2x or 1.5x (I’d probably have falled asleep at 1x pace) and learned a bit.

There are four kinds of developers in the database programming world: builders, designers, programmers and administrators.

This course is not about (#1 above) building a database system, which would involve designing the database interaction with the physical system in C or Assembly or something crazy like that. Nor is it about (#4) maintaining a database in use, which involves optimizing resources, minimizing downtime and keeping things running.

What we’re learning about are choosing a database type, designing schemas, writing queries and incorporating the structure into a program. In other words, this is a database course for people that build database functionality into a program.

There are two choices for databases today: relational databases (in my case, SQLite or some other system that uses SQL as its query language) or hierarchical databases (XML, which means a flat text file formatted in a certain manner).

We were just getting into a description of what XML is when a quiz popped up in the lecture, which was neat.

The questions, however, were ridiculous, not least because I got them all wrong. Here are some things I learned from the quiz (honestly, none of this was discussed in the lecture):

  1. ALWAYS use relational databases when you can. In particular, when the data structure is fixed (a few ‘columns’ and lots of records), relational is the default. Why this is isn’t discussed (grr), but I suspect that relational databases are just much faster.
  2. XML is useful when the data is ‘hierarchical’, which means that data can be easily described as subsets of other parts of the dataset. The example they used in the question was a family tree. For this question I chose ‘XML only’ when the right answer was ‘either XML or relational’. Again, relational is the default and only stray from it IF YOU HAVE A DAMN GOOD REASON TO.

I also learned what ‘relational algebra‘ is. Turns out it isn’t as scary as it sounds. Algebra, I’m reminded, simply means a vocabulary of symbols for concepts. Relational algebra, therefore, can be thought of as a series of symbols that represent actions a database program performs (pi defines the set, sigma selects the data, blah blah blah). I’m hoping it’s somewhat intuitive.

I’m happy I got this out of the way early because seeing the words RELATIONAL ALGEBRA staring out at me from the syllabus was giving me the heebeejeebees. The last thing I need to do is brush up on lots of complicated math.

It it takes FOREVER to relearn math. 

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