Another lecture, another language. This one is the Tuple Relational Calculus for specifying 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 IT Careers Fair and the Careers in Computer Games evening next week; as well as the story of Facebook Graph Search as an example of the power of database query languages.
Link: Slides for Lecture 6
Inside Google Spanner, the Largest Single Database on Earth.
Cade Metz. Wired, 26 November 2012.
Tuple-relational calculus can be quite tricky to understand, and it’s not always obvious to follow what a query means. So, homework this time is to read the lecture slides again, going through the examples to see how each query works. If you are stuck, say so and ask on Piazza.
A timeline of Facebook Graph Search.
More search, less graph.
- Photos tagging Facebook user #4
- Restaurants visited by Mark Zuckerberg
- People who live in Bogota who have visited Fiji
Build your own with http://graph.tips
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