Lecture 6: Tuple Relational Calculus

Title slideToday, another language for talking about databases. This one is the Tuple Relational Calculus for writing queries that describe information to be extracted from the linked tables of a relational database. There’s a separation of roles here: the tuple relational calculus is good for succinctly stating what we want to find out; while relational algebra from the last lecture describes how to combine and sift tables to extract that information from the data. We distinguish what information we want from how to compute it.

There were also announcements about the CompSoc bowling trip, and the Equalise week of events raising funds for the Edinburgh Rape Crisis Centre.

Link: Slides for Lecture 6; Recording

Homework

1. Read This

Student taking notesEither or both of these study guides.

Both are good, but only wikiHow has those pictures.

2. Do This

Work through the exercises for Tutorial 2: Relational Modelling. For more practice, try some of the additional examples.

References

Mark Zuckerberg announcing Facebook Graph SearchA timeline of Facebook Graph Search.
describe
From 2013 …

… to 2016

More search, less graph.

Some of those examples:

Build your own with http://graph.tips

How it’s Done

Read the technical paper by the computer scientists who built this:

Unicorn: A System for Searching the Social Graph
Presented at the 39th International Conference on Very Large Data Bases, VLDB 2013

“Unicorn is designed to answer billions of queries per day at latencies in the hundreds of milliseconds…”

Equalise Film Screening

Poster advertising event