دوره Using Databases with Python ، فصل 4 : Many-to-Many Relationships in SQL

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In this section we explore how to model situations like students enrolling in courses where each course has many students and each student is enrolled in many courses.

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And we can't put a foreign key in Books pointing to Authors because that would be sort of a one on either side. I'm going to make a User table, the main difference is I'm going to give the primary key for the users, I'm going to make a Course table, and this is our standard primary key stuff. Yep, I've got a course and user, primary key, title, id, name, just exactly what we've got.

What unique means is if you try to insert the same string into this column, you know like chuck twice, then it's going to fail the second time because it's going to refuse to create a new record. Some people would just give this to you in a text file and have you cut and paste this, and then go run that in your SQLite browser to create them. Whereas, when you enter the commit, it's going to go and write everything to disk, pause until it's complete, and then your program doesn't continue.

I'm very happy to be here meeting Doctor Chuck and other fellow students. I'm really having fun with Doctor Chuck, and it's great that he can be here in Mexico City so. Hi I'm my first time in Coursera, and I'm very thankful with Doctor Chuck, and happy to meet some of my fellow students.

But Robert's remark ultimately changed billions of dollars of valuation in the Samsung versus Apple stock prices. And so I didn't want to make Minix like a big commercial thing because I figured the BSD guys were eventually are going to go out there and it's a stable mature system with many programmers, and many users, and all software. And there you go and there's a slight glitch of maybe a couple of hundred milliseconds for the application when there was no file service but they don't know that, unless you're doing hard real time, everything works.

And of course we're going to ask URL open to give us back the headers, as a dictionary, using this call and we can see what the, how many we have left for the remaining, right? And then what we're going to do is write a loop that goes through all the friends of this particular user that we're asking and get their screen name, print it out and then we're going to check to see if this one is already in our people database. So what I'm going to do is change this code a little bit really quick, and I'm going to print the headers of rate limiting at the beginning.

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