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• Is there really such a thing as "being good at math"?

  - by thezhaba

  Aside from gifted individuals able to perform complex calculations in their head, I'm wondering if proficiency in mathematics, namely calculus and algebra, has really got to do with one's natural inclination towards sciences, if you can put it that way. A number of students in my calculus course pick up material in seemingly no time whereas I, personally, have to spend time thinking about and understanding most concepts. Even then, if a question that requires a bit more 'imagination' comes up I don't always recognize the concepts behind it, as is the case with calculus proofs, for instance. Nevertheless, I refuse to believe that I'm simply not made for it. I do very well in programming and software engineering courses where a lot of students struggle. At first I could not grasp what they found to be so difficult, but eventually I realized that having previous programming experience is a great asset -- once I've seen and made practical use of the programming concepts learning about them in depth in an academic setting became much easier as I have then already seen their use "in the wild". I suppose I'm hoping that something similar happens with mathematics -- perhaps once the practical idea behind a concept (which authors of textbooks sure do a great job of concealing..) is evident, understanding the seemingly dry and symbolic ideas and proofs would be more obvious? I'm really not sure. All I'm sure of is I'd like to get better at calculus, but I don't yet understand why some of us pick it up easily while others have to spend considerable amounts of time on it and still not have complete understanding if an unusual problem is given.

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• Non Technical -Got selected in Well Reputed Organisation but not getting offer letter. What to do..?

  - by Devashri

  Hi, I got selected in a well reputed company on 27th of March for .Net technology and got selection letter. I was told that I will have to join in next 15 days as my notice peroid was 15 days. And I will get my offer letter as I will submit all documents. So I submitted all the documents and I resigned from my curent organisation. But now no communication is being done. I tried to communicate with them but got no respone. Now I resigned from my previous organisation and not getting offer from new one. So what should I do now? I am just waitng for offer letter and looking for another opportunity? Can anyone suggest me the way to get my offer letter..?? I know this question is nontechnical but still I am asking because I would get suggestions or what to do as by IT Professionals who might had gone through the same condition.

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• MySQL count problem

  - by Skuja

  I have 3 tables users(id,name),groups(id,name) and users_groups(user_id,group_id). users and groups have many to many relationship, so the third one is for storing users and groups relations. I would like to select all the data from groups with user count in each group. So far I came up with this: SELECT groups.*, COUNT(users_groups.user_id) AS user_count FROM groups LEFT JOIN users_groups ON users_groups.group_id = groups.id The problem is that query result is not returning any of groups which has no users (users_groups doesnt have any records with group_id of those groups). How should I create my query to select all the groups and they user count, or user count as 0 if there are no users for that group?

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• threading.Event wait function not signaled when subclassing Process class

  - by user1313404

  For following code never gets past the wait function in run. I'm certain I'm doing something ridiculously stupid, but since I'm not smart enough to figure out what, I'm asking. Any help is appreciated. Here is the code: import threading import multiprocessing from multiprocessing import Process class SomeClass(Process): def __init__(self): Process.__init__(self) self.event = threading.Event() self.event.clear() def continueExec(self): print multiprocessing.current_process().name print self print "Set:" + str(self.event.is_set()) self.event.set() print "Set:" + str(self.event.is_set()) def run(self): print "I'm running with it" print multiprocessing.current_process().name self.event.wait() print "I'm further than I was" print multiprocessing.current_process().name self.event.clear() def main(): s_list = [] for t in range(3): s = SomeClass() print "s:" + str(s) s_list.append(s) s.start() raw_input("Press enter to send signal") for t in range(3): print "s_list["+str(t)+"]:" + str(s_list[t]) s_list[t].continueExec() raw_input("Press enter to send signal") for t in range(3): s_list[t].join() print "All Done" if __name__ == "__main__": main()

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• MySQL: Limit output according to associated ID

  - by Jess

  So here's my situation. I have a books table and authors table. An author can have many books... In my authors page view, the user (logged in) can click an author in a tabled row and be directed to a page displaying the author's books (collected like this URI format: viewauthorbooks.php?author_id=23), very straight forward... However, in my query, I need to display the books for the author only, and not all books stored in the books table (as i currently have!) As I am a complete novice, I used the most simple query of: SELECT * FROM tasks_tb This returns the books for me, but returns every single value (book) in the database, and not ones associated with the selected author. And when I click a different author the same books are displayed for them...I think everyone gets what I'm trying to achieve, I just don't know how to perform the query. I'm guessing that I need to start using more advanced query clauses like INNER JOIN etc. Anyone care to help me out :)

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• Should I use early returns in C#?

  - by Bobby

  I've learned Visual Basic and was always taught to keep the flow of the program without interruptions, like Goto, Exit and Return. Using nested ifs instead of one return statement seems very natural to me. Now that I'm partly migrating towards C#, I wonder what the best practice is for C-like languages. I've been working on a C# project for some time, and of course discover more code of ExampleB and it's hurting my mind somehow. But what is the best practice for this, what is more often used and are there any reasons against one of the styles? public void ExampleA() { if (a != b) { if (a != c) { bool foundIt; for (int i = 0; i < d.Count && !foundIt; i++) { if (element == f) foundIt = true; } } } } public void ExampleB() { if (a == b) return; if (a == c) return; foreach (object element in d) { if (element == f) break; } }

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• Is Amazon SQS the right choice here? Rails performance issue.

  - by ole_berlin

  I'm close to releasing a rails app with the common networking features (messaging, wall, etc.). I want to use some kind of background processing (most likely Bj) for off-loading tasks from the request/response cycle. This would happen when users invite friends via email to join and for email notifications. I'm not sure if I should just drop these invites and notifications in my Database, using a model and then just process it with a worker process every x minutes or if I should go for Amazon SQS, storing the messages and invites there and let my worker retrieve it from Amazon SQS for processing (sending the invites / notifications). The Amazon approach would get load off my Database but I guess it is slower to retrieve messages from there. What do you think?

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• In SQL How do I copy values from one table to another based on another field's value?

  - by Joshua1729

  Okay I have two tables VOUCHERT with the following fields ACTIVATIONCODE SERIALNUMBER VOUCHERDATADBID UNAVAILABLEAT UNAVAILABLEOPERATORDBID AVAILABLEAT AVAILABLEOPERATORDBID ACTIVATIONCODENEW EXT1 EXT2 EXT3 DENOMINATION -- I added this column into the table. and the second table is VOUCHERDATAT with the following fields VOUCHERDATADBID BATCHID VALUE CURRENCY VOUCHERGROUP EXPIRYDATE AGENT EXT1 EXT2 EXT3 What I want to do is copy the corresponding VALUE from VOUCHERDATAT and put it into DENOMINATION of VOUCHERT. The linking between the two is VOUCHERDATADBID. How do I go about it? It is not a 1:1 mapping. What I mean is there may be 1000 SERIALNUMBERS with a same VOUCHERDATADBID. And that VOUCHERDATADBID has only entry in VOUCHERDATAT, hence one value. Therefore, all serial numbers belonging to a certain VOUCHERDATADBID will have the same value. Will JOINS work? What type of JOIN should I use? Or is UPDATE table the way to go? Thanks for the help !!

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• Reduce the number of queries in EF

  - by Gio2k

  I have the following Model: Entities: Product (Contains basic data for products: price, etc) Attribute (Contains data for all possible optional attributes) ProductAttribute (Contains data for optional attributes of a product, eg. Color, Model, Size). ProductAttribute is essentially a many to many relationship with payload (ProductId, AttributeID, Value) And this piece of code: private static void ListAttributes(Product p) { p.ProductAttributes.Load(); foreach (var att in p.ProductAttributes) { att.Attribute.load(); Console.WriteLine("\tAttribute Name:{0} - Value {1}", att.Attribute.Name, att.AttributeValue); } } This piece of code will fire a query for each time the att.Attribute.Load() method is called in the foreach loop, only so i can get display the name of the attribute. I would like to fetch the Attribute.Name together with the query that fetches all attribute values, i.e. join ProductAttribute and Attribute. Is there any way to achieve this within my method?

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• Property changing null whilst updating a value.

  - by dinesh

  retreiveing the Data object through a class which is partial class in linq to sql. i am using the same object model to update the changes. but proprertychanging is always null for this object. An anonoymoustype has been converted into strong object type. This strong type is updated again. any one can expalin reason for this? Sample Code: var questions = from Question in _db.CheckListInstanceQuestionDataSource join Question in _db.QuestionDataSource on CheckListInstanceQuestion.UI_QuestionID equals Question.UI_QuestionID where CheckListInstanceQuestion.UI_CheckListInstanceID == instanceID && CheckListInstanceForm.UI_TemplateCheckListFormID == selectedFormID orderby CheckListInstanceQuestion.IN_Order, CheckListInstanceQuestion.VC_Code select new { Question .UI_QuestionID, Question.VC_Description, }; ICollection checkListQuestions = new List(); foreach (var question in questions) { checkListQuestions.Add(new CheckListInstanceQuestion { UI_QuestionID = question.UI_QuestionID, VC_Description = question.VC_Description, });

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• Linq to Sql query reuse

  - by UserControl

  Let's say we have a view V1 and V2 that is declared like: create view V2 as select V1.*, V2.C1, V2.C2, V2.C3 from V1 join V2 on V1.Key = V2.Key where bla-bla So V2 narrows down the result set of V1 and adds some joins. And there is a retrieval routine in C# IEnumerable<V1> GetData(MyFilter filter, MySortOrder order) {} I want to reuse with V2. Is it possible without performing joins in L2S rather than in database? Should i manually create a base class in the database context or something?

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• Failing faster when URL content is not found, howto

  - by Jam

  I have a thread pool that loops over a bunch of pages and checks to see if some string is there or not. If String is found, or not found response is near instant, however if server is offline or application is not running getting a rejection seems to take seconds How can I change my code to fail faster? for (Thread thread : pool) { thread.start(); } for (Thread thread : pool) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } } Here is my run method @Override public void run() { for (Box b : boxes) { try { connection = new URL(b.getUrl()).openConnection(); scanner = new Scanner(connection.getInputStream()); scanner.useDelimiter("\\Z"); content = scanner.next(); if (content.equals("YES")) { } else { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } catch (Exception ex) { System.out.println("\tFAILED ON " + b.getName() + " BAD APPLICATION STATE"); } } }

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• Why I get UnsupportedOperationException when trying to remove from the List?

  - by Pentium10

  I have this code: public static String SelectRandomFromTemplate(String template,int count) { String[] split = template.split("|"); List<String> list=Arrays.asList(split); Random r = new Random(); while (list.size()>count) { list.remove(r.nextInt(list.size())); } return StringUtils.join(list, ", "); } I get this: 06-03 15:05:29.614: ERROR/AndroidRuntime(7737): java.lang.UnsupportedOperationException 06-03 15:05:29.614: ERROR/AndroidRuntime(7737): at java.util.AbstractList.remove(AbstractList.java:645) How would be this the correct way? Java.15

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• socket.error: [Errno 10054]

  - by C0d3r

  import socket, sys if len(sys.argv) !=3 : print "Usage: ./supabot.py <host> <port>" sys.exit(1) irc = sys.argv[1] port = int(sys.argv[2]) sck = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sck.connect((irc, port)) sck.send('NICK supaBOT\r\n') sck.send('USER supaBOT supaBOT supaBOT :supaBOT Script\r\n') sck.send('JOIN #darkunderground' + '\r\n') data = '' while True: data = sck.recv(1024) if data.find('PING') != -1: sck.send('PONG ' + data.split() [1] + '\r\n') print data elif data.find('!info') != -1: sck.send('PRIVMSG #darkunderground supaBOT v1.0 by sourD' + '\r\n') print sck.recv(1024) when I run this code I get this error.. socket.error: [Errno 10054] An existing connection was forcibly closed by the remote host it says that the error is in line 16, in data = sck.recv(1024)

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• Get the count of A -> B and B->A without duplicates

  - by TomGasson

  I have a table like so: index|from | to ------------------ 1 | ABC | DEF 2 | ABC | GHI 3 | ABC | GHI 4 | ABC | JKL 5 | ABC | JKL 6 | ABC | JKL 7 | DEF | ABC 8 | DEF | GHI 9 | DEF | JKL 10 | GHI | ABC 11 | GHI | ABC 12 | GHI | ABC 13 | JKL | DEF And I need to count how the total times between the points (regardless of direction) to get the result: A | B | count ----------------- ABC | DEF | 2 ABC | GHI | 5 ABC | JKL | 3 DEF | GHI | 1 DEF | JKL | 2 So far I can get: SELECT `a`.`from` as `A`, `a`.`to` as `B`, (`a`.`count` + `b`.`count`) as `count` FROM (SELECT `from`, `to`, count(*) as `count` FROM `table` GROUP BY 1,2) `a` LEFT OUTER JOIN (SELECT `from`,`to`, count(*) as `count` FROM `table` GROUP BY 1,2) `b` ON `a`.`from` = `b`.`to` AND `a`.`to` = `b`.`from` But I'm unsure how to remove the A/B swapped duplicates.

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• Need to speed up the results of this SQL statement. Any advice?

  - by jeffself

  I've got the following SQL Statement that needs some major speed up. The problem is I need to search on two fields, where each of them is calling several sub-selects. Is there a way to join the two fields together so I call the sub-selects only once? SELECT billyr, billno, propacct, vinid, taxpaid, duedate, datepif, propdesc FROM trcdba.billspaid WHERE date(datepif) > '01/06/2009' AND date(datepif) <= '01/06/2010' AND custno in (select custno from cwdba.txpytaxid where taxpayerno in (select taxpayerno from cwdba.txpyaccts where accountno in (select accountno from rtadba.reasacct where controlno = 1234567))) OR custno2 in (select custno from cwdba.txpytaxid where taxpayerno in (select taxpayerno from cwdba.txpyaccts where accountno in (select accountno from rtadba.reasacct where controlno = 1234567)))

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• mysql select query optimization

  - by Saharsh Shah

  I have two table testa & testb. CREATE TABLE `testa` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `testb` ( `id` INT(10) NOT NULL AUTO_INCREMENT, `name` VARCHAR(50) DEFAULT NULL, `aid1` INT(10) DEFAULT NULL, `aid2` INT(10) DEFAULT NULL, `aid3` INT(10) DEFAULT NULL, PRIMARY KEY (`id`) ); Currently I am running below query for retrieving all rows where id in testa table matches with any columns of aid1,aid2,aid3 in tableb. The query is retreiving acurate result but it is taking minimum 30 seconds to execute which is too much. I have also tried to optimise my query using UNION but failed to do so. SELECT a.id, a.name, b.name, b.id FROM testb b INNER JOIN testa a ON b.aid1 = a.id OR b.aid2 = a.id OR b.aid3 = a.id ; How do i optimize my query so it's total execution time is within 2-3 seconds? Thanks in advance...

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• [MFC] What is the reciprocal of CComboBox.GetItemData?

  - by Hamish Grubijan

  Instead of associating objects with Combo Box items, I associate long ids representing choices. They come from a database, so it seems natural to do so anyway. Now, I persist the id and not the index of the user's selection, so that the choice is remembered across sessions. If id no longer exists in database - no big deal. The choice will be messed up once. If db does not change, however, then it would be a great success ;) Here is how I get the id : chosenSomethingIndex = cmbSomething.GetCurSel(); lastSomethingId = cmbSomething.GetItemData(chosenSomethingIndex); How do I reverse this? When I load the stored value for user's last choice, I need to convert that id into an index. I can do: cmbSomething.SetCurSel(chosenSomethingIndex); However, how can I attempt (it might not exist) to get an index once I have an id? I am looking for a reciprocal function to GetItemData I am using VS2008, probably latest version of MFC, whatever that is. Thank you.

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• Referencing outer query's tables in a subquery

  - by soulmerge

  Is it possible to reference an outer query in a subquery with MySQL? I know there are some cases where this is possible: SELECT * FROM table t1 WHERE t1.date = ( SELECT MAX(date) FROM table t2 WHERE t2.id = t1.id)` ); But I'm wondering if something like this could work: SELECT u.username, c._postCount FROM User u INNER JOIN ( SELECT p.user, COUNT(*) AS _postCount FROM Posting p --# This is the reference I would need: WHERE p.user = u.id ) c ON c.user = u.id WHERE u.joinDate < '2009-10-10'; I know I could achieve the same using a GROUP BY or by pulling the outer WHERE clause into the sub-query, but I need this for automatic SQL generation and cannot use either alternative for various other reasons.

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• SQL query showing element more than once.

  - by Sorin Cioban

  Hi guys, I have the following SQL query but it doesn't entirely work because it shows each element more than once. select c.name, c.director, c.title, count(c.title) as numfilms from casting c join casting c1 on c1.name = c.name Group by c.name, c.director, c.title Having count (c.title) > 1 order by numfilms So what it does it shows which actors have made more than 1 film. But unfortunately, this query shows each actor as many times as the number of movies he made. Using distinct doesn't work as actor may have been in different movie with same title and different director.

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• Tell me how to use ActiveRecord#after_add

  - by Small Wolf

  Hey,Guys! Now I hava a problem,how can I make the callback#after_add receive a reference to the join model in a has_many :through association? my code like this: class Emergency has_many :departments, :through => :eme_references, :after_add => Proc.new { |eme_reference| eme_reference.eme_flag = 1} end the attribute eme_flag is the model EmeReference's attribute! but in the block ,i get the eme_reference.class is Emergency. I want to set the attribute eme_flag of the model EmeReference. That is my question! cheers!

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• Limit text area value and cut the rest

  - by streetparade

  I have a textarea which users can enter some tags. I need to limit this tags to 20 tags. Tags could be enterer this way maytag1,mytag2,mytag3 What i wrote is this function function limitTags() { var tags = $("input[type=text][name=tags]").val() var tag = $.trim(tags); var selected = new Array(); /** * replace the last ',' */ if(tag.substring(tag.length - 1) == ",") { *///tag = tag.replace(tag.length - 1, ''); } var enteredTags = tag.split(","); if( enteredTags.length > 20 ) { //$("input[type=text][name=tags]").val(enteredTags.join(",", enteredTags)); alert("Only 20 Tags allowed"); } } The alert works just fine but, after the alert box is gone. i can continiue entering tags till the alert box appears. What i need is cut the text after the messagebox which was entered also the last "," I hope i could ask my question clear. Thanks

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• Zend Framework Relations vs. Table Select

  - by rtmilker

  Hey! I just want to know your guys opinion on using join tables within the zend framework. Of course you can use relations by defining a referenceMap and dependentTables and stuff, or using setIntegrityCheck(false) within a db select(). The setIntegrityCheck version seems a little bit dirty to me, but the other version is not very suitable for big querys and joining many tables... I'm a PHP developer for 5 years now and new to the zend framework and just want get a direction for my first project. Thanks!!!

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• UPDATE from SELECT complains about more that one value returned

  - by Álvaro G. Vicario

  I have this data structure: request ======= building_id lot_code building ======== building_id lot_id lot === lot_id lot_code The request table is missing the value for the building_id column and I want to fill it in from the other tables. So I've tried this: UPDATE request SET building_id = ( SELECT bu.building_id FROM building bu INNER JOIN lot lo ON bu.lot_id=lo.lot_id WHERE lo.lot_code = request.lot_code ); But I'm getting this error: Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , , = or when the subquery is used as an expression. Is it due to wrong syntax? The data model allows more than one building per lot but actual data doesn't contain such cases so there should be at most one building_id per lot_code.

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• MySQL - Conflicting WHERE and GROUP BY Statements

  - by TaylorPLM

  I have a query returning the counts of some data, but I do NOT want data that has a null value in it... As an example, the code rolls stats from a clicking system into a table. SELECT sh.dropid, ... FROM subscriberhistory sh INNER JOIN subscriberhistory sh2 on sh.subid = sh2.subid WHERE sh.dropid IS NOT NULL AND sh.dropid != "" ... GROUP BY sh.dropid An example of the record set returned would look like this... 400 2 3 4 5 6 401 2 3 6 5 4 NULL 2 3 4 5 1 There are some other where clauses, and a few more selects (as I said, using the count aggregate) that are also within the query. There is also an order by statement. Again, the goal is to keep the NULL data out of the preceding record set. Could someone explain to me why this behavior is occurring and what to do to solve it.

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