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• SQL - logical AND among multiple rows

  - by potrnd

  Hello, First of all sorry that I could not think of a more descriptive title. What I want to do is the following using only SQL: I have some lists of strings, list1, list2 and list3. I have a dataset that contains two interesting columns, A and B. Column A contains a TransactionID and column B contains an ItemID. Naturally, there can be multiple rows that share the same TransactionIDs. I need to catch those transactions that have at least one item ID that exists whithin each list (list1, list2 AND list3). I also need to count how many times does that happen for each transaction. I hope that makes enough sense, perhaps I will be able to explain it better with a clear head. Thanks in advance

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• base pointer to derived class

  - by Jay

  Suppose there are Base class and Derived class. Base *A = new Base; Here A is a pointer point to Base class, and new constructs one that A points to. I also saw Base *B = new Derived; How to explain this? B is a pointer to Base Class, and a Derived class constructed and pointed by B? If there is a function derived from Base class, say, Virtual void f(), and it's been overridden in Derived class, then B->f() will invoke which version of the function? version in Base class, or version that overridden in Derived Class. What if there is a new function void g()in Derived, is B->g() going to invoke this function properly? One more is, is int *a = new double; or int *a = new int; legal?

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• Can I use a single pointer for my hash table in C?

  - by aks

  I want to implement a hash table in the following manner: struct list { char *string; struct list *next; }; struct hash_table { int size; /* the size of the table */ struct list **table; /* the table elements */ }; Instead of struct hash_table like above, can I use: struct hash_table { int size; /* the size of the table */ struct list *table; /* the table elements */ }; That is, can I just use a single pointer instead of a double pointer for the hash table elements? If yes, please explain the difference in the way the elements will be stored in the table?

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• Graphics Question: How do I restrict the mouse cursor to within a circle?

  - by Dan

  I'm playing with XNA. When I click the left mouse button, I record the X,Y co-ordinates. Keeping the mouse button held down, moving the mouse draws a line from this origin to the current mouse position. I've offset this into the middle of the window. Now, what I'd like to do is restrict the mouse cursor to within a circle (with a radius of N, centred on the middle of the screen). Restricting the mouse to a rectangular region is easy enough (by adjusting the origin by the difference of the mouse position and the size of the region), but I haven't a clue on how to start doing it for a circular region. Can anyone explain how to do this? Any advice on where to start would be helpful.

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• JavaScript return method

  - by user1314034

  I'am new in javascript. I can't understand why the function returns T1 object (not just string 'hi') in the following example. function T1(){ return 'hi'; } function T(){ return new T1(); } T(); output: T1 And returns function in the following example function T1(){ return function(){ return 'hi'; } } function T(){ return new T1(); } T(); output: function (){ return 'hi' } Please explain this rethult. Thank you)

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• Performance problem on a query.

  - by yapiskan

  Hi, I have a performance problem on a query. First table is a Customer table which has millions records in it. Customer table has a column of email address and some other information about customer. Second table is a CommunicationInfo table which contains just Email addresses. And What I want in here is; how many times the email address in CommunicationInfo table repeats in Customers table. What could be the the most performer query. The basic query that I can explain this situation is; Select ci.Email, count(*) from Customer c left join CommunicationInfo ci on c.Email1 = ci.Email or c.Email2 = ci.Email Group by ci.Email But sure, it takes about 5, 6 minutes in execution. Thanks in Advance.

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• Solution to compiler warning for generic varargs

  - by TJR

  A puzzle from this blog. Similar to SO1445233. Given the following source listing, explain why the compiler is producing a warning at invocation to the list method and give a solution for removing the warning without resorting to @SuppressWarnings annotation. public class JavaLanguagePuzzle3 { public static void main(String[] args) { list("1", 2, new BigDecimal("3.5")); } private static <T> List<T> list(T... items) { return Arrays.asList(items); } } Warning: Type safety: A generic array of Object&Serializable&Comparable<?> is created for a varargs parameter

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• How to get the set events of a control?

  - by Jack

  It's possible via C# code get an list of methods/delegates that was set to Control? let me explain better.. For example. Assuming some definitions like this: foo.Click += (a, b) => { ... } //.. foo.Click += (A,B) => { ... } And a megic method: var baa = foo.GetEvents("Click"); Returns baa[0] points to (a, b) => { ... } baa[1] points to (A,B) => { ... } My scenery: I make and add dynamically event to some controls inside a loop. I want depending to a boolean value a event of control of index one,will removed by using control.Click -= baa[1] or something like this. I hope this is clear for your. Thanks in advance.

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• Executing functions in series

  - by Latanmos

  Hi, First of all... Happy new year! Could you please explain to me, how does this work? I browsed throught Connect's (https://github.com/senchalabs/connect) source code, but I don't get it. I would like to write it by myself. app.get( '/', function(req, res, next) { // Set variable req.var = 'Happy new year!'; // Go to next function next(); }, function(req, res, next) { // Returns 'Happy new year!' console.log(req.var); // <- HOW IS THIS POSSIBLE? // (...) } ); Thanks in advance!

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• wp7 and dependency property : onChanged and onRead?

  - by user233150

  hi here's my question : well I want build a wp7 control,so I write it and all go well, but the problem is that I can intercept on write(see onItemsSourcePropertyChanged)but not on read I would like explain better: public static readonly DependencyProperty ItemsSourceProperty= DependencyProperty.Register( "ItemsSource", typeof(ObservableCollection<ObjWithDesc>), typeof(HorizontalListBox), new PropertyMetadata(OnItemsSourcePropertyChanged) ); static void OnItemsSourcePropertyChanged(DependencyObject obj,DependencyPropertyChangedEventArgs e) { ((HorizontalListBox) obj).OnItemsSourcePropertyChanged(e); } OnItemsSourcePropertyChanged is called when I use SetValue(dp,..) but there isn't onItemsSourcePropertyRead ? that is called when I Use GetValue()? thanks

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• Alert Box Running First?

  - by corymathews

  I have some jQuery/JS below. The first thing to run is the alert box at the end. $(document).ready(function() { $("#id1 img , .msg").stop().animate( { width: '300px', height: '300px'}, { duration: 'slow', easing: 'easeInSine' }).pause(3000); $(".msg").animate( { width: '50px', height: '50px' }, { duration: 498, easing: 'easeOutSine' }); $("#id1 img").animate( { width: '50px', height: '50px' }, { duration: 500, easing: 'easeOutSine' }); $("#id1 img , .msg").animate( { width: '300px',height: '300px'}, { duration: 'slow', easing: 'easeInSine' }).pause(3000); alert('eh?'); }); I do have a easing plugin. If I run this the alert will show, and then the first animate will happen in the background but not be shown. It will just appear at the final size. Shouldn't the alert run at the end of all the animation? Can anyone explain why this is happening?

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• Threads in JAVA

  - by theband

  I was today asked in an interview over the Thread concepts in JAVA? The Questions were... What is a thread? Why do we go for threading? A real time example over the threads. Can we create threads in Spring framework service class. Can flex call a thread? I did not answer any questions apart from definition of Thread, that too i just learnt from internet. Can anyone explain me clearly over this.

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• Which of these Array Initializations is better in Ruby?

  - by Bragaadeesh

  Hi, Which of these two forms of Array Initialization is better in Ruby? Method 1: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = Array.new(DAYS_IN_A_WEEK.size).map!{ Array.new(HOURS_IN_A_DAY.size) } DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day][hour] = 'something' end end Method 2: DAYS_IN_A_WEEK = (0..6).to_a HOURS_IN_A_DAY = (0..23).to_a @data = {} DAYS_IN_A_WEEK.each do |day| HOURS_IN_A_DAY.each do |hour| @data[day] ||= {} @data[day][hour] = 'something' end end The difference between the first method and the second method is that the second one does not allocate memory initially. I feel the second one is a bit inferior when it comes to performance due to the numerous amount of Array copies that has to happen. However, it is not straight forward in Ruby to find what is happening. So, if someone can explain me which is better, it would be really great! Thanks

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• Problem building relationships between models

  - by Brian Roisentul

  Until now, I've been using acts_as_taggable_on plugin for tagging announcements. That plugin creates the following tables: taggings: relates tags and announcements table(for the tagged item, it has a field called taggable_id, which I rename to "announcement_id" for what I'll explain below). tags: has the tag ids and names. The other day, I discovered that I had no way of getting the announcements tagged with a certain tag, but doing Announcement.tagged_with(tag_name), and I don't want to search by name, but for id. So, as I'm using almost nothing of the functionality in that plugin, I decided to create the models for taggings and tags tables, to accomplish this: Announcement.tags. The models' relationships look as following: class Tagging < ActiveRecord::Base belongs_to :announcement belongs_to :tag end class Tag < ActiveRecord::Base has_many :announcements, :through => :taggings end class Announcement < ActiveRecord::Base has_many :tags, :through => :taggings Why can't I execute the command Announcement.tags? Because when I try, I get undefined method `tags'

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• Suspension of Gmail account [closed]

  - by Ifeanyi Agu

  I have a Joomla site with my gmail account (google apps) being used as the SMTP server for sending mails. I also have a newsletter component on this site. I tried sending newsletter to all my subscribers and I noticed that the SMTP server could not be connected to. I then checked the emails of my company and noticed that the one I used to set it up was suspended. I cannot really explain why Google suspended the email account. Please could anyone tell me if Google saw the mails that were being sent as spam.

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• Why javabeans framework create the IndexedPropertyDescriptor for the NON index method

  - by George Macus

  I'm not familiar with java beans framework, in the below scenario, I got the IndexedPropertyDescriptor for the method getFooWithX, could someone explain why? public class IntrospectorTest { public static void main(String[] args) throws IntrospectionException { BeanInfo info = Introspector.getBeanInfo(SubClass.class); PropertyDescriptor[] descriptors = info.getPropertyDescriptors(); for (int i = 0; i < descriptors.length; i++) { System.out.println(descriptors[i].getClass().getName() + ":" + descriptors[i].getName()); } } } abstract class BaseClass { public abstract Object getFoo(); } abstract class SubClass extends BaseClass { public Object getFooWithX(int x) { return null; } } and the result will be: java.beans.PropertyDescriptor:class java.beans.PropertyDescriptor:foo java.beans.IndexedPropertyDescriptor:fooWithX Why?

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• What is this VB6 method doing?

  - by Craig

  We are converting a VB6 application to C# (4.0). and have come across a method in VB6 that we're battling to understand. Public Sub SaveToField(fldAttach As ADODB.Field) Dim bData() As Byte Dim nSize As Long nSize = Len(m_sEmail) bData = LngToByteArray(nSize) fldAttach.AppendChunk bData If nSize > 0 Then bData = StringToByteArray(m_sEmail) fldAttach.AppendChunk bData End If nSize = Len(m_sName) bData = LngToByteArray(nSize) fldAttach.AppendChunk bData If nSize > 0 Then bData = StringToByteArray(m_sName) fldAttach.AppendChunk bData End If bData = LngToByteArray(m_nContactID) fldAttach.AppendChunk bData End Sub It seems like it's doing some binary file copy type thing, but I'm not quite understanding. Could someone explain so that we can rewrite it?

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• Problem with "not declared in this scope" error

  - by lego69

  I've got: error a1 was not declared in this scope Can somebody please explain why this code causes that? quiz.h #ifndef QUIZ_H_ #define QUIZ_H_ #include "quiz.cpp" class A { private: int player; public: A(int initPlayer); ~A(); void foo(); }; #endif /* QUIZ_H_ */ quiz.cpp #include "quiz.h" #include <iostream> using std::cout; using std::endl; A::A(int initPlayer = 0){ player = initPlayer; } A::~A(){ } void A::foo(){ cout << player; } main function #include "quiz.h" int main() { quiz(7); return 0; } quiz function #include "quiz.h" void quiz(int i) { A a1(i); a1.foo(); }

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• Python and object/class attrs - what's going on?

  - by digitala

  Can someone explain why Python does the following? >>> class Foo(object): ... bar = [] ... >>> a = Foo() >>> b = Foo() >>> a.bar.append(1) >>> b.bar [1] >>> a.bar = 1 >>> a.bar 1 >>> b.bar [1] >>> a.bar = [] >>> a.bar [] >>> b.bar [1] >>> del a.bar >>> a.bar [1] It's rather confusing!

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• About Attributes member of LUID_AND_ATTRIBUTES used in TOKEN_PRIVILEGES structure

  - by Astaroth

  MSDN article, Enabling and Disabling Privileges in C++, provided the a code example to show how to enable or disable a privilege in an access token. I quote the part in questioned: tp.PrivilegeCount = 1; tp.Privileges[0].Luid = luid; if (bEnablePrivilege) tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED; else tp.Privileges[0].Attributes = 0; What is the meaning of zero value for Attributes member? According to the documentation of TOKEN_PRIVILEGES structure, the attributes of a privilege can be a combination of the following values: SE_PRIVILEGE_ENABLED  (it is 0x00000002L in WinNT.h) SE_PRIVILEGE_ENABLED_BY_DEFAULT  (it is 0x00000001L in WinNT.h) SE_PRIVILEGE_REMOVED  (it is 0x00000004L in WinNT.h) SE_PRIVILEGE_USED_FOR_ACCESS  (it is 0x80000000L in WinNT.h) So, we don't see any valid constant with a value of zero. I guess, the zero is equal to SE_PRIVILEGE_REMOVED. Anybody here could explain what the zero value really does?

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• Reference and Value confusion

  - by rgamber

  Hi I read this question on Stack overflow, and tried to do an example. I had the below code: public static void main(String[] args){ int i = 5; Integer I = new Integer(5); increasePrimitive(i); increaseObject(I); System.out.println(i); //Prints 5 - correct System.out.println(I); //Still prints 5 System.out.println(increaseObject2(I)); //Still prints 5 } public static void increasePrimitive(int n){ n++; } public static void increaseObject(Integer n){ n++; } public static int increaseObject2(Integer n){ return n++; } Does the increaseObject print 5 because the value of reference is changing inside that function? Am I right? I am confused why the increasedObject2 prints 5 and not 6. Can anyone please explain?

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• Does '[ab]+' equal '(a|b)+' in python re module?

  - by user1477871

  I think pat1 = '[ab]' and pat2 = 'a|b' have the same function in Python(python2.7, windows) 're' module as a regular expression pattern. But I am confused with '[ab]+' and '(a|b)+', do they have the same function, if not plz explain details. ''' Created on 2012-9-4 @author: melo ''' import re pat1 = '(a|b)+' pat2 = '[ab]+' text = '22ababbbaa33aaa44b55bb66abaa77babab88' m1 = re.search(pat1, text) m2 = re.search(pat2, text) print 'search with pat1:', m1.group() print 'search with pat2:', m2.group() m11 = re.split(pat1, text) m22 = re.split(pat2, text) print 'split with pat1:', m11 print 'split with pat2:', m22 m111 = re.findall(pat1, text) m222 = re.findall(pat2, text) print 'findall with pat1:', m111 print 'findall with pat2:', m222 output as below: search with pat1: ababbbaa search with pat2: ababbbaa split with pat1: ['22', 'a', '33', 'a', '44', 'b', '55', 'b', '66', 'a', '77', 'b', '88'] split with pat2: ['22', '33', '44', '55', '66', '77', '88'] findall with pat1: ['a', 'a', 'b', 'b', 'a', 'b'] findall with pat2: ['ababbbaa', 'aaa', 'b', 'bb', 'abaa', 'babab'] why are 'pat1' and 'pat2' different and what's their difference? what kind of strings can 'pat1' actually match?

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• iPhone App on iPad - What is the extra effort?

  - by hol

  I started to develop an iPhone App for a client but the binary not yet submitted to Apple. My client asked me whether they can run the iPhone App also on the iPad. I am not sure what to answer. I am away from home and cannot even check how this all works in XCode. I wonder whether I have to submit two binaries two Apple - one for iPhone and one for iPad - or how this all works? If somebody with experience can explain me. Basically I need to figure out how much more effort I have to consider if it is only making the app work on the iPad. I do not mean the effort to redesign the whole app being a real "iPad app". Just to make it work and when somebody downloads the app and it can be for an iPhone and for an iPad and it does not matter.

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• MySql query and table optimisation

  - by Cheeky

  Hi everyone. I am trying to run the following simple query on a table with 500K records. SELECT COUNT(*) AS impressionCount FROM impression WHERE 0 = 0 AND impressionObjectId1 = 'C69A54B8-B828-E2E4-2319A93011DF4120' AND impressionObjectId2 = '1'; This query is taking 10 seconds to run. I have tried creating individual indexes for the impressionObjectId1 and impressionObjectId2 columns, as well as a composite index using both. The composite worked well for a while, but now it is also slow. Here is my table structure: DROP TABLE IF EXISTS `impression`; CREATE TABLE `impression` ( `impressionId` varchar(50) NOT NULL, `impressionObjectId1` varchar(50) NOT NULL, `impressionObjectId2` varchar(50) default NULL, `impressionStampDate` datetime NOT NULL, PRIMARY KEY (`impressionId`), KEY `IX_object` (`impressionObjectId1`,`impressionObjectId2`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 ROW_FORMAT=DYNAMIC COMMENT='InnoDB free: 191488 kB'; Any advice would be greatly appreciated. Thanks EDIT: When adding an EXPLAIN, this is the output: 1, 'SIMPLE', 'impression', 'ref', 'IX_object', 'IX_object', '105', 'const,const', 304499, 'Using where; Using index'

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• What is this PHP Syntax: ($variation_id>0) ? $variation_id : $item_id;

  - by user1325258

  Is someone able to explain the meaing of the following statment, and the type of php it is reffering to so I can do further research: $foo = ($variation_id>0) ? $variation_id : $item_id; I have tried search but don't really know what i'm searching for. What I am trying to find out is the name and meaning of the following syntax ? / : and is ($variation_id>0) just a shorthand if statement ? -- I just stumbled upon conditional variables although a nice simple explanation would still be appreciated.

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