Title slide
Slides : Recording

This afternoon the final lecture on Structure Data covered a range of database topics: ACID properties for transactions; the NoSQL movement; nested SQL queries, set operations, and aggregate queries; ultimate physical limits to computation; the wonders of the heavens captured in SkyServer; and the idea of doing scientific research and experiments from inside the database.

Links: Slides for Lecture 8; Recording of Lecture 8


Explore SkyServer, its different types of search, and try some SQL yourself. Work through at least the first three pages of the SQL Tutorial there.

Links: SkyServer; Famous places; SQL tutorial

SkyServer accepts queries from anyone and everyone: you don’t need an account or identity on it unless you want to run queries that return more than 100,000 rows or take over 10 minutes. If you manage to hit that limit, let me know — I’m interested to find out how.

  1. Watch the night sky go by

  2. Work out how https://is.gd/locatepluto persuades SkyServer to serve a non-dwarf-planet version of Pluto.

    There’s a real SQL query there, and the page is genuinely from SkyServer. Some browsers may complain about subversive activity here, and they are right to do so.

Pie chart of popularity share for different kinds of database management system Which Database Systems are Most Popular?
Despite what you may have heard, relational databases still rule

This 2014 article from ZDNet looks at a ranking of database popularity. Since then things have shifted a little, but RDBMS remain well ahead.

Link: ZDNet article; Live popularity pie chart

Database popularity chart DB-Engines
Knowledge Base of Relational and NoSQL Database Management Systems

Each month DB-Engines ranks database management systems by “popularity”, looking at job offers, Google trends, tweets, …

Links: DB-Engines; This month’s top 10

Hubble Telescope image of Hoag's Object Hoag’s Object
Ring Galaxy

Eight billion stars, 600 million light-years away, shaped like a doughnut and with a bright inner core.

Links: Hubble Telescope image; Wikipedia

If you are interested in databases, their implementation and application, I recommend the third-year course Database Systems. If you would like to know more about complexity and the limits of computation, then take Algorithms and Data Structures.

The material in this lecture on complexity, exponential growth, and physical limits to computation is not examinable in this course, but these are important concepts in computer science and very likely to turn up again in your studies here.

Last of All
Movie Poster Travelling Salesman: The Movie
Four mathematicians are hired by the US government to solve the most powerful problem in computer science history.

“The moral uncertainty of a P=NP world” — New Scientist

Yes, really. You can watch the trailer. The casting, sadly, buys into the persistent nonsense that computer scientists are necessarily young, white, male and American. If you can face that, then the maths is said to be sound, and the desert/coin analogy in the trailer is a great image for the nature of P vs. NP. What’s less clear is whether showing P=NP would have quite the social and political impact suggested.

Lecture 8: SQL Queries