|
Thread Rules
1. This is not a "do my homework for me" thread. If you have specific questions, ask, but don't post an assignment or homework problem and expect an exact solution.
2. No recruiting for your cockamamie projects (you won't replace facebook with 3 dudes you found on the internet and $20)
3. If you can't articulate why a language is bad, don't start slinging shit about it. Just remember that nothing is worse than making CSS IE6 compatible.
4. Use [code] tags to format code blocks. |
On October 26 2018 19:45 bo1b wrote:I know it's possible like that, but I'm asking if it's possible to subtract in anyway. I found this schema out of a textbook: https://d2vlcm61l7u1fs.cloudfront.net/media/86b/86b4f72e-7407-4e33-af28-e90aacc10ccc/php4ZZyIW.pngLets say you're trying to find the amount of copies remaining at specific library branch, using an aggregate count might not work, depending on how they've set up the schema. If all they've done is input that there are 5 copies of Casino Royal at that library, and 2 separate people have loaned a copy from that library, how can you output the correct answer? I'm just trying to find out if you can do arithmetic from one column of data (assuming they're both numbers) to another, which I don't think is possible (or I never learned, which is more likely).
With SQL you can use basic arithmetic. Of course, SQL is not pure relational algebra, so don't know if that answers your question.
E: of course, the question you're asking isn't actually about relational algebra. Which is, per definition, about the relations in your database, not about manipulating individual values. So just as you cannot do string operations in relational algebra, you cannot do arithmetic operations: it's simply not what the algebra is for.
|
That's what I figured, I've been given a certain question relating to it and I don't want to ask for the answer online. Meaning the tutors either explained the problem wrong or I'm reading the question wrong.
|
Hyrule19161 Posts
you can select the book you're checking from book_copies, then join on book_loans and subtract the count(id) of that book.
Also it's odd there's no return_date column in book_loans
|
There is a due date though.
How do you subtract in relational algebra? Could you give an example if possible?
|
On October 27 2018 05:23 bo1b wrote:
There is a due date though.
How do you subtract in relational algebra? Could you give an example if possible?
Due date shouldn't tell you if the book has been checked in or not. It should be checked in before the due date and it being past due doesn't mean it was turned in.
|
Ah, yeah I see what you mean. I think it's just a homework assignment, and they weren't being particularly enthusiastic in creating it.
|
I've been using fzf on my linux install, and man oh man is it good. I've put this in my bashrc:
alias m="WD\$(pwd);cd ;mpv \"\$(fzf)\";cd \$wd"
and opening a terminal, and pushing m pulls up a library of every file in my home directory. Typing in a few letters of the show I want to watch narrows it down, and selcting it and pushing enter pulls it up on my screen in mpv. If I know what I want to watch it takes all of about 2 seconds to load up the video and start watching; more to the point I've done something similar with zathura for ebooks; now I have a library without the shitty reader that callibre provides, and it's so so fast.
This post brought to you by surplus autism™
|
For once in my life I am trying to plan out my project before jumping into it but I'm struggling to nail down exactly how I want to do some things in terms of design.
I am making a debate site. It has Debates, Posts, Communities, and Users. Posts belong to Debates and Users. Debates belong to Communities and Users. Communities belong to Users. I'll probably need to add Teams and Coalitions.
There are different types of Debates. For example, Direct Debates(1v1 or team v team), Coalition Debates(team vs team with subteams with different objectives).
It seems to me that each type of Debate should be a subclass of Debate. However, I am having problems understanding how to configure that. In a Coalition debate, if Team A and B are in a Coalition, and Team C and D are in a Coalition, then the debate order goes A, C, B, D. However, how would I assign this order to the Debate? I am thinking of having simply, Post A, Post C, Post B, Post D and they must be in order, but this seems like a terrible solution.
|
On a entirely unrelated note, do you think that at some point in the future Serverless providers will switch to simply using WebAssembly for all of their different types of languages, rather than having to specifically enable certain languages?
|
On November 01 2018 10:46 WarSame wrote:
For once in my life I am trying to plan out my project before jumping into it but I'm struggling to nail down exactly how I want to do some things in terms of design.
I am making a debate site. It has Debates, Posts, Communities, and Users. Posts belong to Debates and Users. Debates belong to Communities and Users. Communities belong to Users. I'll probably need to add Teams and Coalitions.
There are different types of Debates. For example, Direct Debates(1v1 or team v team), Coalition Debates(team vs team with subteams with different objectives).
It seems to me that each type of Debate should be a subclass of Debate. However, I am having problems understanding how to configure that. In a Coalition debate, if Team A and B are in a Coalition, and Team C and D are in a Coalition, then the debate order goes A, C, B, D. However, how would I assign this order to the Debate? I am thinking of having simply, Post A, Post C, Post B, Post D and they must be in order, but this seems like a terrible solution.
This is horribly confusing. I don't think anybody cares about"belonging" for any of those things, except posts. Maybe throw that draft away and focus on the basics:
What is a debate? Is it just a thread? Is it a thread with rules? Is it moderated?
What is the structure of your community? You mention users and community, but then mention teams and coalitions. What are these things? Can users belong to multiple teams? Can teams be in multiple coalitions? Is there something happening at community level, or is it just the set of all users? Are teams and coalitions managed in some way?
|
On November 01 2018 17:30 Acrofales wrote:Show nested quote +On November 01 2018 10:46 WarSame wrote:
For once in my life I am trying to plan out my project before jumping into it but I'm struggling to nail down exactly how I want to do some things in terms of design.
I am making a debate site. It has Debates, Posts, Communities, and Users. Posts belong to Debates and Users. Debates belong to Communities and Users. Communities belong to Users. I'll probably need to add Teams and Coalitions.
There are different types of Debates. For example, Direct Debates(1v1 or team v team), Coalition Debates(team vs team with subteams with different objectives).
It seems to me that each type of Debate should be a subclass of Debate. However, I am having problems understanding how to configure that. In a Coalition debate, if Team A and B are in a Coalition, and Team C and D are in a Coalition, then the debate order goes A, C, B, D. However, how would I assign this order to the Debate? I am thinking of having simply, Post A, Post C, Post B, Post D and they must be in order, but this seems like a terrible solution. This is horribly confusing. I don't think anybody cares about"belonging" for any of those things, except posts. Maybe throw that draft away and focus on the basics: What is a debate? Is it just a thread? Is it a thread with rules? Is it moderated? What is the structure of your community? You mention users and community, but then mention teams and coalitions. What are these things? Can users belong to multiple teams? Can teams be in multiple coalitions? Is there something happening at community level, or is it just the set of all users? Are teams and coalitions managed in some way?
I agree with the idea of having specific debate types as subclasses of Debate. I also agree with what Acrofales is saying, and that some of the things you say should _have_ users, posts, etc., but not necessarily belong to them. I also don't understand what a community is, to me the community is the entire site.
In my mind the Debate is responsible for managing a debate. A Debate has (among other things): rules (how the debate is structured), teams (at least two), moderators, at least 1 thread (depends on the debate type, maybe some are private), and whatever else you think of that is necessary to actually carry out the debate. Some things floating around in my head: a 1v1 Debate limits the number of teams to 2 and the team size to 1, a coalition debate has a CoalitionTeam instead of a regular Team, each Debate subclass defines the Rules of the debate.
|
On November 01 2018 17:30 Acrofales wrote:Show nested quote +On November 01 2018 10:46 WarSame wrote:
For once in my life I am trying to plan out my project before jumping into it but I'm struggling to nail down exactly how I want to do some things in terms of design.
I am making a debate site. It has Debates, Posts, Communities, and Users. Posts belong to Debates and Users. Debates belong to Communities and Users. Communities belong to Users. I'll probably need to add Teams and Coalitions.
There are different types of Debates. For example, Direct Debates(1v1 or team v team), Coalition Debates(team vs team with subteams with different objectives).
It seems to me that each type of Debate should be a subclass of Debate. However, I am having problems understanding how to configure that. In a Coalition debate, if Team A and B are in a Coalition, and Team C and D are in a Coalition, then the debate order goes A, C, B, D. However, how would I assign this order to the Debate? I am thinking of having simply, Post A, Post C, Post B, Post D and they must be in order, but this seems like a terrible solution. This is horribly confusing. I don't think anybody cares about"belonging" for any of those things, except posts. Maybe throw that draft away and focus on the basics: What is a debate? Is it just a thread? Is it a thread with rules? Is it moderated?
I used belonging to refer to a "has-a" relationship. So a Debate has Posts. I also need to track this stuff to see, for example, who made a specific Debate.
What is the structure of your community? You mention users and community, but then mention teams and coalitions. What are these things? Can users belong to multiple teams? Can teams be in multiple coalitions? Is there something happening at community level, or is it just the set of all users? Are teams and coalitions managed in some way?
A Community has Users that are subscribed to it, and contains Debates within it. I think I might rename it a Forum. It's similar to a Subreddit.
A Team is a group of co-operating Users within a Debate. A Coalition is a group of co-operating Teams to represent a side. The classic example of a Coalition Debate is France and Austria vs. Britain and Prussia to mirror the Napoleonic Wars.
Users cannot belong to multiple Teams. Teams cannot be in multiple Coalitions. Communities are collections of Debates posted to that Community and subscribed Users. Yes, I envision Teams and Coalitions being defined at the start of Debate, with modification possible with agreement between the Moderator(which I haven't thought much about yet), and both sides.
On November 01 2018 18:23 emperorchampion wrote:Show nested quote +On November 01 2018 17:30 Acrofales wrote:On November 01 2018 10:46 WarSame wrote:
For once in my life I am trying to plan out my project before jumping into it but I'm struggling to nail down exactly how I want to do some things in terms of design.
I am making a debate site. It has Debates, Posts, Communities, and Users. Posts belong to Debates and Users. Debates belong to Communities and Users. Communities belong to Users. I'll probably need to add Teams and Coalitions.
There are different types of Debates. For example, Direct Debates(1v1 or team v team), Coalition Debates(team vs team with subteams with different objectives).
It seems to me that each type of Debate should be a subclass of Debate. However, I am having problems understanding how to configure that. In a Coalition debate, if Team A and B are in a Coalition, and Team C and D are in a Coalition, then the debate order goes A, C, B, D. However, how would I assign this order to the Debate? I am thinking of having simply, Post A, Post C, Post B, Post D and they must be in order, but this seems like a terrible solution. This is horribly confusing. I don't think anybody cares about"belonging" for any of those things, except posts. Maybe throw that draft away and focus on the basics: What is a debate? Is it just a thread? Is it a thread with rules? Is it moderated? What is the structure of your community? You mention users and community, but then mention teams and coalitions. What are these things? Can users belong to multiple teams? Can teams be in multiple coalitions? Is there something happening at community level, or is it just the set of all users? Are teams and coalitions managed in some way? I agree with the idea of having specific debate types as subclasses of Debate. I also agree with what Acrofales is saying, and that some of the things you say should _have_ users, posts, etc., but not necessarily belong to them. I also don't understand what a community is, to me the community is the entire site. In my mind the Debate is responsible for managing a debate. A Debate has (among other things): rules (how the debate is structured), teams (at least two), moderators, at least 1 thread (depends on the debate type, maybe some are private), and whatever else you think of that is necessary to actually carry out the debate. Some things floating around in my head: a 1v1 Debate limits the number of teams to 2 and the team size to 1, a coalition debate has a CoalitionTeam instead of a regular Team, each Debate subclass defines the Rules of the debate.
I guess I mis-used the term "belong".
Thank you for your stab at it there. I think I like it. I think for Rules I could make an Interface that all Debates must implement to control how they go through their phases.
|
|
|
He definiteley wants to be a friends class of her
|
|
|
![[image loading]](https://i.imgur.com/VkNDVW7.png)
Finally something to send to your friends and family...
|
Some stuff I'm dealing with at work:
SQL query built with Java JDBC, called from Scala, called from Python, called from bash script...
![[image loading]](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTVkf5CMujaz6K7ayCmeSzJZ5mh_Nd5z2_-7UYsluGMF54wSPkS)
|
|
|
FLASK vs Django?
I'm working on a university project and trying to decide which framework would be better for us (group project). Here is the info about the project and the members that are of note:
- Group project (3 of us) due in 2 weeks
- Need to design a user interface for our database server (website backed by DB)
- MySQL was used for database design
- We all have fairly decent python experience (and I'd like to think we are all capable people, willing and able to learn - even in this short amount of time)
- We have little to no web development experience
I know there are plenty of differences from what online (although both would work). I may be wrong, but I think the most important factor for us would be which framework allows us to work and connect to MySQL most easily.
Thank you so much to people who reply, it will be super appreciated!
|
I have not worked with Django. Ive used Flask with sqlite, not MySQL, but my experience was that it was very straightforward to use. I dont think you can really go wrong with it.
|
|
|
|
|
|
EPT![[image loading]](https://i.imgur.com/WzfOzGf.jpg)
