CS50 SQL - Lecture 1 - Relating

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This is CS50, Harvard University's introduction to the intellectual enterprises of computer science and the art of programming.

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TABLE OF CONTENTS

00:00:00 - Introduction
00:00:17 - Relating
00:08:23 - Entity Relationship Diagrams
00:13:35 - Keys
00:26:35 - Subqueries
00:55:47 - Joins
01:16:59 - Sets
01:30:29 - Groups

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LICENSE

CC BY-NC-SA 4.0
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License

David J. Malan

[mahmudhasanrimel]

Even though I have intermediate knowledge of SQL, I am taking this course to refresh myself. The explanations are crystal clear, and the topics are well-organized. Overall, I would give this course a 5-star rating.

[GenZ__]

Cs50 courses are on another league .
Carter you’re a great teacher.
Thank you all🙏🏽

[vmvknik]

Thank you so much for putting this online and free for us. I'm learning Data Science and getting started with SQL is really easier with your instruction.

[janetkalu]

Thank you for putting this course out for us. I can proudly say that I have never enjoyed querying tables until now. You make it seamless and stuck in my head. I don't have to repeatedly memorize queries, without understanding the underlying concepts. Thank you so much

[WarbossPepe]

You're a great teacher and communicator Carter. Thank you for doing what you do

[kamalkishor]

Great teacher, Awesome way of communication, each concept is crystal clear and easy to understand.
Love to see more videos from you.
Great thing CS50.

💌

[alainrouleau]

Thanks so much!

I finally understand, after all these years, how JOIN actually works and all its variants. Love the animated joins. Very nice to see what happens visually. That helped to explain things quite a lot.

The query within a query, aka as subqueries or nested queries, was all very interesting as well. Didn't realize you could go so deep and do something like that. You know, multiple nested queries all on one line. Pretty crazy.

[SamraatMaharjan]

I am absolutely loving these playlists.

[dixigrc]

Great explaination and so unique way of teaching it help me so much in university 🥰

[SothearithKONGMrMuyKhmer]

Great! Thanks a lot for this tutorial! 🥰

[swampguy]

This guy talks as well as Malan, very good course

[gyhlnpp]

In moneyball ERD have two tables players and salaries. relation between table players and table salaries 1.N but some players LIKE Satchel Paige doesnt have matches, i dont get something or its mistake

[joaopauloduarteferreira]

Where do I take this data bases used in the course?

[mastertoru]

Is there any reason why at 1:09:42, "NULL" did not appear for the presenter?

[shauryathakkar]

Why would we use subqueries if we can use joins instead ???

[sisunbb]

Guys how can i download the software or sqlite shown in this image begginer i wanted to code along with him; your help would be appreciated ❤

[rebekahmenn]

Can anyone figure out why my query is coming back as incorrect? The prompt for Lesson 1, Question 12 in the DESE set of questions is:
"Write a SQL query to find public school districts with above-average per-pupil expenditures and an above-average percentage of teachers rated “exemplary”. Your query should return the districts’ names, along with their per-pupil expenditures and percentage of teachers rated exemplary. Sort the results first by the percentage of teachers rated exemplary (high to low), then by the per-pupil expenditure (high to low)."

And here's my query:

SELECT "districts"."name", "staff_evaluations"."exemplary", FROM "districts"
JOIN "expenditures" ON "expenditures"."district_id" = "districts"."id"
JOIN "staff_evaluations" ON = "districts"."id"
WHERE > (
SELECT
FROM "staff_evaluations"
) AND > (
SELECT
FROM "expenditures"
)
ORDER BY DESC, DESC;

Every time I check my answers, CS50 tells me this is wrong but I can't figure out why.

[cmonvgz]

Do you have the solutions for the problem set?

[tshepomalalane]

Nested querying feels like recursion somehow...

[kursataydn]

I cant see tables in my longlist when i enter ".tables "it just outputs longlist any solution for that? Thanks!