Lecture 5: Relational Algebra

Title slide
Slides : Recording

This morning’s lecture presented a mathematical language for slicing and dicing the structured tables of the relational model: selection, projection, renaming; union, intersection, difference; cross product, join, equijoin and natural join. A key feature of this relational algebra is that just six of these operations are enough to capture an extremely wide range of queries and transformations of data. Database implementors work hard to build highly efficient engines to carry out these operations, which can then support many different kinds of user application.
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Lecture 4: From ER Diagrams to Relational Models

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Slides : Recording

Today’s lecture reviewed the high-level conceptual language of ER diagrams and the more concrete structures of the relational model; followed by some recipes for translating from the first into the second. This isn’t always an exact match, and for any particular ER diagram we might go back to its original scenario description to decide how to best represent it as a relational model. Even so, this kind of step-by-step staging towards a fully formal representation is an effective route to capturing the subtleties of real-world systems.
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Lecture 2: Entities and Relationships

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Slides : Recording

In today’s lecture I started to present the topic of structured data with an introduction to Entity-Relationship Modelling and the graphical language of ER diagrams. This language is important for planning and structuring databases, bridging the gap between informal conceptual design and the logical precision required for machine implementation.

I was also able to demonstrate the marvels of recursion by live-streaming the lecture within itself. Fun, but perhaps we won’t do that again.
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Viewing Lecture Recordings

Feedback from students suggests that viewing lecture recordings isn’t quite as one-click as I had hoped. While I included direct links in the previous blog post and on Piazza, those only work once you have been recognised as an authorized Inf1-DA student by Echo360 who provide the lecture recording service.

If you find that the links don’t work for you then I recommend you do the following.

  • Connect to Learn at https://www.learn.ed.ac.uk.
  • Log on through EASE if necessary.
  • Select Informatics 1 – Data and Analysis (2017-2018)[SV1-SEM2].
  • Select the Lecture Recordings link on the left-hand side.
  • That will attempt to pop-up a new window. Your browser may disallow this — mine did — in which case you can wait a moment until Learn realises that and then select the button offered to open Media Hopper Replay in a new window.

I believe that once you have trodden this path all parties involved will recognise you as a legitimate Inf1-DA student. The one-click links I post here should then work directly.

If you find a simpler method to do this then please let me know.

If you try this and still can’t see the lecture recording, then please let me know.

If you can’t give me a URL to get to it, then it isn’t on the Web.

Lecture 1: Introduction

Title slide
Slides : Recording

Thank you to everyone who came in through the snow and ice for this morning’s lecture. You can find the slides for the lecture by clicking on the thumbnail image of the title slide to the right, or in the links below. In the rest of this post I’ve listed the homework for Friday’s lecture and some answers to questions students asked during and after the lecture.
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