دوره Using Databases with Python ، فصل 2 : Basic Structured Query Language
دربارهی این فصل:
We learn the four core CRUD operations (Create, Read, Update, and Delete) to manage data stored in a database.
این شامل 7 زیر است:
If you imagine something like a learning management system, where there's hundreds of thousands of users, and terabytes or petabytes of data, and you log in, and within a half a second it shows you what you're supposed to see. And so this notion of modeling stuff at a connection is the underlying math that makes databases fast, but when we programmers think about it we kind of think about it as rows and columns. And in the early days they figured out how to technically solve fast access to lots of data by hopping in various ways, indexing, doing clever things.
And so, in a large project, and we're not going to do it in this, so much in this class, but I figured it's time now that we're learning about databases to sort of give you a sense of how they're used in these online systems. And so in a professional environment, like the open source learning management system that I work on named Sakai, in production I don't get as a developer, and so that's who I am. And I write code that talks SQL to the database server and gets data back, and then formats it for the end user, and that's what developers do.
You just need some piece of software that gives you a place to type SQL, You hit a go button, and it sends it to the database and comes back. Now, it turns out that we're kind of implicitly running those commands, the SELECT * FROM Users, every time I hit that browse button. Select all the columns from the table Users, ORDER BY, again a two-word keyword that rolls off the tongue more naturally.
I could make this be a email equals 'csev@umich' I would have to escape the quotes and stuff, but this question mark is a placeholder. So no matter what update does is in a single atomic operation, it turns whatever this number is into one higher and we don't have to worry about other pieces of code potentially modifying it. And this conn.commit, basically the way it works is that the database is efficiently keeping some of the information in memory and at some point, has to write all that stuff out to disk.
I'm studying faculty of electrical engineering and computing at University of Zagreb, and I am graduate student. I'm student of philosophy and social humanistic informatics, graduate and undergraduate. I've taken four, Guide to Irrational Behavior, How to reason and argue, and human computer interaction.
And selection of, I mean, how many variety of application you can build on top of a software foundation, what I call a database management system, is too varied. The files are hierarchical, they were in the IMS, the IBM information management system, which is a tree structure. He started talking about flat file and he called it a table, and it's a very easy concept that everybody understand.
We're gonna use urllib and urllib.error, twurl which was code that augments my url to do all the OAuth calculation. We're gonna make a database, and we have to import SQL because of the way Python doesn't trust any certificates, no matter how good they are. Now remember that you've got to edit the hidden.py file to make this work because we are talking to the Twitter API.
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