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  • Beginner SQL question: arithmetic with multiple COUNT(*) results

    - by polygenelubricants
    Continuing with the spirit of using the Stack Exchange Data Explorer to learn SQL, (see: Can we become our own “Northwind” for teaching SQL / databases?), I've decided to try to write a query to answer a simple question (on meta): What % of stackoverflow users have over 10,000 rep?. Here's what I've done: Query#1 SELECT COUNT(*) FROM Users WHERE Users.Reputation >= 10000 Result: 556 Query#2 SELECT COUNT(*) FROM USERS Result: 227691 Now, how do I put them together into one query? What is this query idiom called? What do I need to write so I can get, say, a one-row three-column result like this: 556 227691 0,00244190592

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  • Getting the median of 3 values using scheme's

    - by kristian Roger
    The problem this time is to get the median of three values (easy) I did this: (define (med x y z) (car(cdr(x y z))) and it was accepted but when testing it: (med 3 4 5) I get this error: Error: attempt to call a non-procedure (2 3 4) And when entering letters instead of number i get: (md x y z) Error: undefined varia y (package user) Using something besides x y z I get: (md d l m) Error: undefined variable d (package user) the question was deleted dont know how anyway write a function that return the median of 3 values Sorry for editing the question I got that I should put the values in order first not just a sill car and cdr thing so I did so 33> (define (med x y z) (if(and( (<x y) (<y z) y if(and( (<y x) (<x z) x z))))) Warning: invalid expression (if (and< (<x y) (<y z) y if (and ((<y x) (<x z) x z)))) but as u see Im getting a warning so what is wronge ?

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  • Pipe implementation

    - by nunos
    I am trying to implement a linux shell that supports piping. I have already done simple commands, commands running in background, redirections, but piping is still missing. I have already read about it and seen some snippets of code, but still haven't been able to sort out a working solution. What I have so far: int fd[2]; pid_t pid = fork(); if (pid == -1) return -1; if (pid == 0) { dup2(0, fd[0]); execlp("sort", "sort", NULL); } I am a novice programmer, as you can probably tell, and when I am programming something I don't know much about, this being obviously the case, I like to start with something really easy and concrete and then build from there. So, before being able to implement three and more different commands in pipeline, I would like to be able to compute "ls names.txt | sort" or something similiar, in which names.txt is a file of names alfabetically unordered. Thanks.

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  • How is thread synchronization implemented, at the assembly language level?

    - by Martin
    While I'm familiar with concurrent programming concepts such as mutexes and semaphores, I have never understood how they are implemented at the assembly language level. I imagine there being a set of memory "flags" saying: lock A is held by thread 1 lock B is held by thread 3 lock C is not held by any thread etc But how is access to these flags synchronized between threads? Something like this naive example would only create a race condition: mov edx, [myThreadId] wait: cmp [lock], 0 jne wait mov [lock], edx ; I wanted an exclusive lock but the above ; three instructions are not an atomic operation :(

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  • rails nested attributes

    - by user342798
    I am using rails 3.0.0.beta3 and I am trying to implement form with nested attributes using :accepts_nested_attributes_for. My form is nested to three levels: Survey Question Answer. Survey has_many Questions, and Question has many Answers. Inside the Survey model, there is :accepts_nested_attributes_for :questions and inside the question mode, there is :accepts_nested_attributes_for :answers Everything is working fine except when I add a new answer to an existing question, it doesn't get created. However, if I make changes to the corresponding question while creating the answer, I can successfully create the answer. This example is exactly similar to a railscast: http://railscasts.com/episodes/197-nested-model-form-part-2 but doesn't work in rails3 (at least in my case). Please let me know if there is any issue with nested attributes in Rails 3. Thanks in advance.

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  • In-Proc SxS opens for shell extension in managed code?

    - by Jens Granlund
    The recommendation used to be "Do not write in-process shell extensions in managed code." But with .NET Framework 4 and In-Process Side-by-Side the main reason not to write shell extensions in managed code should be resolved. With that said, I have three questions. Is it now okay to write shell extensions in managed code? Which problems, if any might there be with writing shell extensions in managed code? What reasons might there be to write shell extensions in unmanaged code?

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  • Base-camp Style Subdomains and IDs of Models

    - by Newy
    I have an app that has Basecamp-style subdomains, that is, I have Projects, Users, Apples and Oranges. The Users, Apples and Oranges are all keyed to a Project and only exist in the http://project.myapp.com. I added a project_id to Users, Apples and Oranges and everything works, except of course that the ids of those three objects increment globally, and throughout my app I lookup objects by that id. This doesn't seem like best practice. Should I instead do lookups by a secondary key? How does that affect efficiency? If there's a good blog post that covers this, would be wesome.

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  • NameError: uninitialized constant Nokogiri::HTML::DocumentFragment

    - by Mike Sutton
    About three hours ago I started seeing the above error in my production server. It comes from a call to the sanitize gem: vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:276:in 'load_missing_constant' vendor/rails/activerecord/lib/../../activesupport/lib/active_support/dependencies.rb:468:in `const_missing' vendor/gems/sanitize-1.2.0/lib/sanitize.rb:91:in `clean!' vendor/gems/sanitize-1.2.0/lib/sanitize.rb:84:in `clean' vendor/gems/sanitize-1.2.0/lib/sanitize.rb:49:in `clean' app/helpers/application_helper.rb:28:in `display_none' app/views/main/_blogs.html.erb:13:in `_run_erb_47app47views47main47_blogs46html46erb' The error only occurs on the production server (linux), not my development machine (windows) I tried rolling back my latest deployment but it didn't fix it. I've updated to sanitize 1.2.0 (which was the latest version brought down by gem update sanitize, though I note my host is running 1.3.6. Can anyone provide any clues to help fix this?

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  • File system to choose for NAS box based on FreeNAS or OpenFiler [closed]

    - by Chris
    I'm a photographer and I have a requirement find a better method of storing my photos other than multiple USB2 drives via USB hubs. Currently I use a Macbook Pro and 6 external drives connected via USB2 or FW800. 3 are a copy of the first three, kept up to day manually by running an rsync backup. I'd like to run a FreeNAS or OpenFiler NAS box using 2TB drives mirrored via software RAID. But - I would like to have the flexibility of also plugging into the drive physically for the faster throughput when necessary. So. My question is, is there a file system that both *nix and Mac OSX will play nice with? Many thanks, Chris.

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  • Connection string in app.config in a class library

    - by Copeleto
    I am creating solution and inside I have three projects: A WCF Service Library Project A DataAccess Project (Class Library) A Web site for hosting WCF service The implementation of the service is on the project # 1, but in order to access the DataBase I use a second project that implements the data access using a class library project. That problem is in order to get data access I need to configure a connection string, but that connection string must be configurable in a production environment, I meant in production I am going to deploy the site, which is a very simple project that contains only a reference WCF Service Library Project then a guy from database department will configure the connection string. In development I have an app.config on the data access project but when I do the release that app.config is embedded on the dll. Any ideas how can we achieve our purpose

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  • How to cut a "hole" inside a rectangular Sprite to see the Sprite underneath? (ActionScript 3)

    - by Zando
    Everytime I google this question I see confusing information about masks and blends, none of which seems to directly apply to what I think should be an easy thing... There are three Sprites involved here...the lowest layer sprite is pretty much a background. I want to overlay a translucent Sprite on top of the background and then I want the third, top-most Sprite to act as a hole, so that the area inside the third Sprite is completely transparent, so that the background sprite is completely visible. How would I go about doing this dynamically (i.e. dynamically drawing the masking sprite and hole using the Actionscript graphics calls)?

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  • On Ubuntu, how do you install a newer version of python and keep the older python version?

    - by Trevor Boyd Smith
    Background: I am using Ubuntu The newer python version is not in the apt-get repository (or synaptic) I plan on keeping the old version as the default python when you call "python" from the command line I plan on calling the new python using pythonX.X (X.X is the new version). Given the background, how do you install a newer version of python and keep the older python version? I have downloaded from python.org the "install from source" *.tgz package. The readme is pretty simple and says "execute three commands: ./configure; make; make test; sudo make install;" If I do the above commands, will the installation overwrite the old version of python I have (I definitely need the old version)?

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  • jQuery addClass to a tag problem

    - by lander
    I have this in my html code: <ul id="navlist" <li id="tabItem1"><a href="#">Item one</a></li> <li id="tabItem2"><a href="#">Item two</a></li> <li id="tabItem3"><a href="#">Item three</a></li> <li id="tabItem4"><a href="#">Item four</a></li> </ul> I want to add a class to the a element with jquery like this: (its not working) var currentTab = 1; $(document).ready(function() { $("li#tabItem" + currentTab + ":has(a)").addClass("navlistHover"); //console.log("li#tabItem" + currentTab + ":has(a)"); }); When a delete the a element and do it like the next example, than there is no problem. $("li#tabItem" + currentTab).addClass("navlistHover");

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  • Will this safely delete my record?

    - by Sergio Tapia
    I hate these three tables that. Two tables have a many to many relationship and as such it generates a third table. I'm using Linq-to-SQL and in the .dbml file I've dragged all the folder there to the graphic surface. Here is the method I'm using to delete an Area safely. Remember that documents are associated to an Area, so I can't just delete it and leave documents hanging. ScansDataContext db = new ScansDataContext(); /// <summary> /// Deletes an Area object from the database along with all associations in the database. /// </summary> /// <param name="area">Area object to save</param> public void Delete(Area area) { db.DocumentAreaRelations.DeleteAllOnSubmit(area.DocumentAreaRelations); db.Areas.DeleteOnSubmit(area); db.SubmitChanges(System.Data.Linq.ConflictMode.FailOnFirstConflict); }

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  • Procedures before checking in to source control?

    - by Mongus Pong
    I am starting to get a reputation at work as the "guy who breaks the builds". The problem is not that I am writing dodgy code, but when it comes to checking my fixes back into source control, it all goes wrong. I am regularly doing stupid things like : forgetting to add new files accidentally checking in code for a half fixed bug along with another bug fix forgetting to save the files in VS before checking them in I need to develop some habits / tools to stop this. What do you regularly do to ensure the code you check in is correct and is what needs to go in? Edit I forgot to mention that things can get pretty chaotic in this place. I quite often have two or three things that Im working on in the same code base at any one time. When I check in I will only really want to check in one of those things.

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  • Insert rows into MySQL table while changing one value

    - by Jonathan
    Hey all- I have a MySQL table that defines values for a specific customer type. | CustomerType | Key Field 1 | Key Field 2 | Value | Each customer type has 10 values associated with it (based on the other two key fields). I am creating a new customer type (TypeB) that is exactly the same as another customer type (TypeA). I want to insert "TypeB" as the CustomerType but then just copy the values from TypeA's rows for the other three fields. Is there an SQL insert statement to make this happen? Somthing like: insert into customers(customer_type, key1, key2, value) values "TypeB" union select key1, key2, value from customers where customer_type = "TypeA" Thanks- Jonathan

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  • How do I create a controller and action without a model?

    - by Angela
    I have several models: Email Letter Call All three belong to a model Campaign. And a Campaign has_many Contacts I envision being able to see a schedule for Today by going to domain/schedule/today What I'd like it to do would be to show all the Events (Email, Letter, Call) that have to happen today for each campaign. I tried the following, but have some challenges in putting it into a controller versus into a View. There are many emails in campaign. Email.days is the number of days from the contact.start_date that an email should be sent to the Contact. ScheduleController < def index campaigns.each do |campaign| #goes through each campaign for contacts in campaign.contacts Email.find(:all).reject { |email| email.contact.start_date + email.days <= Date.now } end end end

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  • Android question. Is there a link to a simple example of changing the screen brightness for an activ

    - by John
    There are apparently at least three different techniques for changing screen brightness in the Android OS. Two of them no longer work post-cupcake and the third accepted technique evidently has a bug. I would like to increase screen brightness at the start of a one-view activity then turn the brightness back to the user setting at the end of the activity. No buttons, no second view or second activity. Just a maxed brightness at start and a return to original brightness setting at the end of the activity. The examples of the current technique using WindowManager.LayoutParams that I have located range from 2 lines of code WindowManager.LayoutParams lp = getWindow().getAttributes(); lp.screenBrightness = 100 / 100.0f; getWindow().setAttributes(lp); to several pages of source code and numerous activities. Is there a simple example of maxing the screen brightness at start that someone can provide a link to? Thank you for reading my question.

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  • non blocking tcp connect with epoll

    - by doccarcass
    My linux application is performing non-blocking TCP connect syscall and then use epoll_wait to detect three way handshake completion. Sometimes epoll_wait returns with both POLLOUT & POLLERR revents set for the same socket descriptor. I would like to understand what's going on at TCP level. I'm not able to reproduce it on demand. My guess is that between two calls to epoll_wait inside my event loop we had a SYN+ACK/ACK/FIN sequence but again I'm not able to reproduce it. Any clue ? Regards, Seb

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  • Assignment to None

    - by Joel
    Hello, I have a function which returns 3 numbers, e.g.: def numbers(): return 1,2,3 usually I call this function to receive all three returned numbers e.g.: a,b,c=numbers() However, I have one case in which I only need the first returned number. I tried using: a, None None = numbers() But I receive "SyntaxError: assignment to None". I know, of course, that i can use the first option I mentioned and then not use "b" and "c", but only "a". However, this seems like a "waste" of two vars and feels like wrong programming. Any ideas? Thanks, Joek

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  • Fit <TD> height to page

    - by ssg
    Consider a table with three rows with heights 10, *, 10. I'd like the middle cell to be high enough to fit to the page vertically. Unfortunately "height:100%" doesn't work at table, tr, or td level, possibly due to standards. Even if it happens to work, I don't want 100%, I want 100% of clientHeight-20px :) I can always write script to calculate remaining clientHeight but I wonder if it can be achieved in HTML/CSS standards. NOTE: I'm using table just for layout, if there are other ways to lay them down in a better way I'm ok with those approaches too.

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  • Edit Distance in Python

    - by Alice
    I'm programming a spellcheck program in Python. I have a list of valid words (the dictionary) and I need to output a list of words from this dictionary that have an edit distance of 2 from a given invalid word. I know I need to start by generating a list with an edit distance of one from the invalid word(and then run that again on all the generated words). I have three methods, inserts(...), deletions(...) and changes(...) that should output a list of words with an edit distance of 1, where inserts outputs all valid words with one more letter than the given word, deletions outputs all valid words with one less letter, and changes outputs all valid words with one different letter. I've checked a bunch of places but I can't seem to find an algorithm that describes this process. All the ideas I've come up with involve looping through the dictionary list multiple times, which would be extremely time consuming. If anyone could offer some insight, I'd be extremely grateful. Thanks!

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  • SQL Join a View with a Table

    - by gamerzfuse
    CREATE VIEW qtyorderedview AS SELECT titleditors.title_id, titleditors.ed_id, salesdetails.title_id, salesdetails.qty_shipped FROM titleditors, salesdetails WHERE titleditors.title_id = salesdetails.title_id I am using the above SQL statement to create a view. I need to show Editors First Name, Last Name, City where they shipped more than 50 books. The three tables I have are: create table editors ( ed_id char(11), ed_lname varchar(20), ed_fname varchar(20), ed_pos varchar(12), phone varchar(10), address varchar(30), city varchar(20), state char(2), zip char(5), ed_boss char(11)); create table titleditors ( ed_id char(11), title_id char(6), ed_ord integer); create table salesdetails ( sonum integer, qty_ordered integer, qty_shipped integer, title_id char(6), date_shipped date); Can anyone tell me what the second Join code would be to create this result? My first view works fine, but I don't know how to join it to the second table to achieve this result? I didn't make the tables, I just have to work with what I was given. Thanks in advance!

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  • Query data using LINQ to SQL and Entity Framework with foreign key? (Help me please)

    - by The Wind
    Hello! There is a problem I need help with your query on the data using LINQ to SQL and Entity Framework (I'm using Visual Studio 2010). My picure here: http://img.tamtay.vn/files/photo2/2010/5/28/10/962/4bff3a3b_1093f58f_untitled-1.gif I have three tables: tbl NewsDetails tblNewsCategories tblNewsInCategories (See screen 1 in my picture) Now, I want to retrieve records in the tblNewsDetails table, with condition: CategoryId=1, as the following results: (See screen 2 in my picture) But NewsID and CategoryId in tblNewsInCategories table is two foreign key, I do not see them and I do not know how to use them in your code. My code has errors: (See screen 3 in my picture) Please help me. Thanks! (I am a new member, should not have the right to insert images)

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  • Symbol error in java application using netbeans when adding a shared project to library

    - by Malachi
    I have a project which has shared functionality between three other projects and have linked these to existing projects as I normally would using the add project functionality of the libraries folder. This all used to work however when I started up Netbeans yesterday it just wasn't working as in the other projects won't compile even though the projects are linked. It can recognise the packages - just the actual classes themselves were not recognised... and to add to the weirdness some of the classes are getting picked up fine. I have checked the dist folder of the shared project and the Shared.jar file exists. Also I have checked the Jar and the other classes that are not being recognises are there also. Any suggestions?

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