TL;DR - do not take CS143 with Rosario. Just not worth it. I made a Bruinwalk account just to post this review in the hope that I can save someone from this class.

Rosario has a massive superiority complex and it seems like he teaches only to get a power trip. He assumes everybody is against him and treats students as such. He is rude and condescending and does not want to help you learn unless you suck up to him at office hours. He cares more about being right and powerful than helping us learn what we joined his class to learn. Tests/specs are unclear, he doesn't like to answer questions, and is borderline abusive on Piazza. A friend of mine was outright cyberbullied by him and others on Piazza, administration did nothing.

I as well as many of my friends have complained to administration about him so I am frankly astonished he is still teaching. This man should not be teaching. Do not think your experience will be different -- do not take this class.

The recent reviews don't lie; the class, and professor rosario, have improved since a majority of the reviews were left. I took it online and we had 5 homeworks, 1 extra credit project with spark, a midterm, and a final. All of which were pretty straightforward, and the curve prof rosario gives is pretty generous. Additionally, I never felt like prof rosario was belittling students like some previous reviewers mentioned; I asked some pretty dumb questions in office hours and class, and never once did prof rosario make me feel like an idiot (even though I probably am at times). I'm not too interested in databases, but I'd recommend most CS majors to take some offering of this course to get a fundamental understanding of databases.

He sucks and I hate him a lot

Rosario has really chilled out since last year. He was a friendly and helpful instructor during Spring 2020. The homework assignments were really doable, and the tests weren't insane.

For the first 10 weeks I really wanted to give a good comment for this professor, because his average response time on Piazza is 40 mins and he is always willing to support students (he gives us an extra 1 hours to do midterm), and his (kinda) engaging lectures. His homework (which is 40% of the grade) is generally not hard, except for the last one or two, and he gives extra credit for the one mini-project.
However, things changed. You wouldn't expect the final would be much much harder than the midterm. In midterm, we have many SQL related problem which is clearly defined in class or in textbook (or slides). Well, in the final, even though we have 24 hours to work on it, many friends of mine and me have to work at least 10 hours for a supposed 3 hours exam (he told us this exam was written for 3 hours). There are a bunch of explanation kind of questions that you can't really find the related information in the textbook (or slides or lectures), and even the textbook doesn't go in detail for those concepts. So, you have to really really think out of the box, and like use what you have learned from the past 20 years maybe, to compose an answer, not to mention that he gives few partial credit for answer that is not in his solution. Putting it simply, it's not just testing what you learn in class, it's like asking you to publish a paper for some of the questions. THIS IS INSANE.
All in all, it's not the kind of easy-A CS elective class you are looking (maybe not even easy-B). However, if you really like database systems, the lectures are good (JUST DON'T TAKE THE EXAM). So if you have other choices of professor teaching this class, go for it.

I remember seeing Rosario get a lot of from prior Bruinwalk reviews and actively tried avoiding him - then I took his class and realized how WRONG those reviews were. He's completely revamped the curriculum post 2019 and it's solid.

Rosario is awesome. His lectures are clear + engaging and follow the slides in lock step (he posts slides prior to lecture, annotates during class, and re-posts after).

Best thing about him is he works in industry as a Data Scientist / SWE, so every topic is covered with practical, real-world examples that we can actually use.

And he's a nice guy who truly enjoys teaching, and he handled COVID better than any other professor I've seen so props!

The professor was really nice and helpful. He answered Piazza posts extremely quickly and thoughtfully.

We had a mini-project for extra credit. This probably bumped my grade up from B+ territory up to an A.

I'm not sure how good his lectures are, since I just looked over the slides, but from the brief snippets of the recording I saw, they seemed okay. His slides, however, are very good, IMO.

There were only 5 homework assignments, and the workload for each of these was not too bad. I think each of these assignments could be done in an afternoon.

The midterm was okay, but the final was a bit harder. I just reviewed the lecture slides, homework assignments, and discussion slides. I received a 88% for the midterm and 80% for the final.

I agree with just about everything else that's been said so far. Here's an example.

One lecture we were discussing how to run transactions serially. The professor mentioned that you can use a topological sort on a precedence graph to obtain the correct order of transactions. He then proceeded to give an incorrect explanation of topological sort. When a student pointed this out, instead of humbly accepting his mistake, Rosario snapped at the student and in a flustered tone, told us to just do a topological sort.

A student watching this all unfold might be thinking that since CS 180 is not a pre-req for CS 143 and since our professor doesn't even know what a topological sort is, this topic will probably never show up again.

Well, on our final, topological sort reappeared even though it had never been discussed again. I guess we were just expected to learn it on our own from one refrenece to it in lecture.

Experiences like this are what make the class so frustrating.

I disagree with a lot of the negative reviews of Rosario and his class. I found his lectures to be pretty engaging and covered the material pretty well. He was also pretty open to helping students.

Content and exams: The lectures in the first half of the course (mainly SQL and relational algebra) covered everything you really need to know and the midterm was very fair in my opinion. The second half of the class was definitely a turning point where the concepts got more difficult (NoSQL, join algorithms, system design, etc.) and the lectures were more congested. The final was extremely difficult and too long in my opinion, but as long as you did well in the rest of the class you should have been fine. Overall, I feel I learned what I needed to without being too overwhelmed. (Another note, he uses a lot of the questions from previous midterms. He does not give back the final though).

Homework: There were 6, all of which were relatively easy and not super intensive. Covered the most relevant material too.

Textbook: Rosario gives a textbook as a basis for the class, though it is not necessarily needed. I would recommend reading it though as it is pretty good at explaining the concepts and fills in the blanks Rosario might have missed.

Overall, don't be scared off by the bad reviews. The class is worth taking and gives you the fundamental understanding of databases you need, just be prepared for some difficult exams.

One of my favorite courses I have taken at UCLA. Prof. Rosario really knows his stuff. I thought the assignments were extremely fair and the exams in lecture felt representative of what was displayed on exams. Some of the exam questions proved to be quite tricky but Prof. Rosario's expectations seem to reflect that students are learning and is willing to fairly represent the grades. Felt like I learned a lot about data management systems not only just hands on content but also some theory and internals for how data management systems work. Would highly recommend this class for all computer scientists.