Lecture 4 pre-recording

Hello everyone,

Remember that there is no physical lecture today. Instead, we have a pre-recorded video, which is now published. It is a bit longer than one lecture is supposed to be. It is not ideal, but I believe that it is better to finish the SQL summary in one piece (we will compensate this time later with a shorter lecture). Remember also that it is a `crash course' on SQL, so it is a bit denser than usual lectures. There are also a couple of small glitches in the video (no more than 1 min in total), hopefully they will not disturb you too much. We will start with discussions about this lecture material next time. See you on Wednesday!

Egor