Another day, 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 next week, and information about 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.