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• Designing Relational Survey Questionnaires Database

  - by user1213055

  I'm trying to build a simple sql database for following access database. Currently there is no relationship and I just have two tables male and female with 6 sections in each form. How can I design it a better way so end user can connect to the database and analyze using STATA or SPSS ? I'm really confused whether I should create one table with all fields or break down into different tables. The database is specific to this study only so I'm not looking for a generic survey database where user can create surveys and capture them. Any feedback or suggestion is much appreciated.

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• building an XML service parsing library

  - by DanInDC

  This is more of a design question I suppose. My company offers a web service to our client that spits data out in a custom xml format. I'd like to build a java library we can offer so our customers can just feed it the url and we will turn it into a set of POJOs built from the response. I can obviously just create a library that will do some simple xml parsing and building of the POJOs but I'm looking to build something a bit more robust. My brain is pulling me in a million directions, wondering if anyone has some pointers or some code to poke at. Was thinking about adding an Abdera extension, but it's not really a syndication format that fits the Abdera model. And most of the popular service libraries (twitter, facebook) all rely on standards format parsers, of which our format isn't.

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• Why and How to avoid Event Handler memory leaks ?

  - by gillyb

  Hey There, I just came to realize, by reading some questions and answers on StackOverflow, that adding event handlers using += in C# (or i guess, other .net languages) can cause common memory leaks... I have used event handlers like this in the past many times, and never realized that they can cause, or have caused, memory leaks in my applications. How does this work (meaning, why does this actually cause a memory leak) ? How can I fix this problem ? Is using -= to the same event handler enough ? Are there common design patterns or best practices for handling situations like this ? Example : How am I supposed to handle an application that has many different threads, using many different event handlers to raise several events on the UI ? Are there any good and simple ways to monitor this efficiently in an already built big application ? Thanks in advance!

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• Javascript object encapsulation that tracks changes

  - by Raynos

  Is it possible to create an object container where changes can be tracked Said object is a complex nested object of data. (compliant with JSON). The wrapper allows you to get the object, and save changes, without specifically stating what the changes are Does there exist a design pattern for this kind of encapsulation Deep cloning is not an option since I'm trying to write a wrapper like this to avoid doing just that. The solution of serialization should only be considered if there are no other solutions. An example of use would be var foo = state.get(); // change state state.update(); // or state.save(); client.tell(state.recentChange()); A jsfiddle snippet might help : http://jsfiddle.net/Raynos/kzKEp/ It seems like implementing an internal hash to keep track of changes is the best option. [Edit] To clarify this is actaully done on node.js on the server. The only thing that changes is that the solution can be specific to the V8 implementation.

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• SQL Server concurrency and generated sequence

  - by Goyuix

  I need a sequence of numbers for an application, and I am hoping to leverage the abilities of SQL Server to do it. I have created the following table and procedure (in SQL Server 2005): CREATE TABLE sequences ( seq_name varchar(50) NOT NULL, seq_value int NOT NULL ) CREATE PROCEDURE nextval @seq_name varchar(50) AS BEGIN DECLARE @seq_value INT SET @seq_value = -1 UPDATE sequences SET @seq_value = seq_value = seq_value + 1 WHERE seq_name = @seq_name RETURN @seq_value END I am a little concerned that without locking the table/row another request could happen concurrently and end up returning the same number to another thread or client. This would be very bad obviously. Is this design safe in this regard? Is there something I can add that would add the necessary locking to make it safe? Note: I am aware of IDENTITY inserts in SQL Server - and that is not what I am looking for this in particular case. Specifically, I don't want to be inserting/deleting rows. This is basically to have a central table that manages the sequential number generator for a bunch of sequences.

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• Return an opaque object to the caller without violating type-safety

  - by JS Bangs

  I have a method which should return a snapshot of the current state, and another method which restores that state. public class MachineModel { public Snapshot CurrentSnapshot { get; } public void RestoreSnapshot (Snapshot saved) { /* etc */ }; } The state Snapshot class should be completely opaque to the caller--no visible methods or properties--but its properties have to be visible within the MachineModel class. I could obviously do this by downcasting, i.e. have CurrentSnapshot return an object, and have RestoreSnapshot accept an object argument which it casts back to a Snapshot. But forced casting like that makes me feel dirty. What's the best alternate design that allows me to be both type-safe and opaque?

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• How to relate keywords to records - Many to Many

  - by webworm

  Hi All, I am looking for suggestions on database design for a sample jobs listing application. I have many jobs that I would like to associate various keywords with. Each job can have multiple keywords. I would like to store the keywords in a seperate table instead of in a field within the Job table so as to avoid mispellings in keywords. What is the best way to relate keywords to the jobs? I was thinking of using an intermediary table that would have a many to many relationship linking keywords to jobs. Is this the best way to go or should I just have a field in the Job table that contains multiple keywords? Thanks for any suggestions.

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• benefit of having a factory for object creation?

  - by ajsie

  I'm trying to understand the factory design pattern. I don't understand why it's good to have a middleman between the client and the product (object that the client wants). example with no factory: $mac = new Mac(); example with a factory: $appleStore = new AppleStore(); $mac = $appleStore->getProduct('mac'); How does the factory pattern decouple the client from the product? Could someone give an example of a future code change that will impact on example 1 negative, but positive in example 2 so I understand the importance of decoupling? Thanks.

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• Entity framework Update fails when object is linked to a missing child

  - by McKay

  I’m having trouble updating an objects child when the object has a reference to a nonexising child record. eg. Tables Car and CarColor have a relationship. Car.CarColorId CarColor.CarColorId If I load the car with its color record like so this var result = from x in database.Car.Include("CarColor") where x.CarId = 5 select x; I'll get back the Car object and it’s Color object. Now suppose that some time ago a CarColor had been deleted but the Car record in question still contains the CarColorId value. So when I run the query the Color object is null because the CarColor record didn’t exist. My problem here is that when I attach another Color object that does exist I get a Store update, insert error when saving. Car.Color = newColor Database.SaveChanges(); It’s like the context is trying to delete the nonexisting color. How can I get around this?

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• How to add values accordingly of the first indices of a dictionary of tuples of a list of strings? Python 3x

  - by TheStruggler

  I'm stuck on how to formulate this problem properly and the following is: What if we had the following values: {('A','B','C','D'):3, ('A','C','B','D'):2, ('B','D','C','A'):4, ('D','C','B','A'):3, ('C','B','A','D'):1, ('C','D','A','B'):1} When we sum up the first place values: [5,4,2,3] (5 people picked for A first, 4 people picked for B first, and so on like A = 5, B = 4, C = 2, D = 3) The maximum values for any alphabet is 5, which isn't a majority (5/14 is less than half), where 14 is the sum of total values. So we remove the alphabet with the fewest first place picks. Which in this case is C. I want to return a dictionary where {'A':5, 'B':4, 'C':2, 'D':3} without importing anything. This is my work: def popular(letter): '''(dict of {tuple of (str, str, str, str): int}) -> dict of {str:int} ''' my_dictionary = {} counter = 0 for (alphabet, picks) in letter.items(): if (alphabet[0]): my_dictionary[alphabet[0]] = picks else: my_dictionary[alphabet[0]] = counter return my_dictionary This returns duplicate of keys which I cannot get rid of. Thanks.

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• Drupal and Back-End Complexity

  - by Brian

  Currently I am working on a school website, and we are still in the decision-making process of choosing a framework (we know that we're not using Joomla! or hand-coding). Drupal came up as a viable choice, and currently, that is my best bet for the site. However, I have an issue with CMS's in general. I would like to develop a quite complicated and specifically custom-suited back-end application for teachers to interact with individual students, including the design of shared/custom calendars, announcement privileges, etc. I currently have a bit of expertise with HTML, CSS, PHP, MySQL, and I could wrap my head around some JavaScript and AJAX stuff if need-be. However, would such a complicated application work with Drupal (in that I could create it to specifically suite my purposes)?

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• Importing data and keeping ids and relationships

  - by Justin Hamade

  I am working on cleaning up a mess that another programmer started. The created 2 identical databases for different locations but that obviously caused major issues. They are using cakePHP and there are quite a few relationships. I am pretty sure I will have to write a script to import that data from on DB to the other and keep all the relationships but was wondering if there is an easier way to do it.

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• How should nested components interact with model in a GUI application?

  - by fig-gnuton

  Broad design/architecture question. If you have nested components in a GUI, what's the most common way for those components to interact with data? For example, let's say a component receives a click on one of its buttons to save data. Should the save request be delegated up that component's ancestors, with the uppermost ancestor ultimately passing the request to a controller? Or are models/datastores in a GUI application typically singletons, so that a component at any level of a hierarchy can directly get/set data? Or is a controller injected as a dependency down the hierarchy of components, so that any given component is only one intermediary away from the datastore/model?

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• MYSQL to UPDATE table if row with 2 specific columns exist or INSERT new row if it does not exist

  - by user2509541

  I have a MYSQL table that looks as follows: id id_jugador id_partido team1 team2 1 2 1 5 2 2 2 2 1 1 3 1 2 0 0 I need to create a query to either INSERT new rows in the table or UPDATE the table. The condition is based on id_jugador and id_partido, meaning that if I wanted to insert id_jugador = 2 and id_partido = 1, then it should just UPDATE the existing row with the new team1 and team2 values I am sending. And dont duplicate the row. However, if I have an entry id_jugador=2 and id_partido=3, since this combination does not exist yet, it should add the new row. I read about the REPLACE INTO but it seems to be unable to check combination of UNIQUE KEYS.

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• Solution for this SQL query?

  - by homeWorkBoy

  Suppose you have these tables: Table Name: Salesman Fields: S_ID(Primary Key), Name Table Name: Region_1 Fields: Reg_ID(Primary Key), S_ID(Foreign Key), sales Table Name: Region_2 Fields: Reg_ID(Primary Key), S_ID(Foreign Key), sales Table Name: Region_3 Fields: Reg_ID(Primary Key), S_ID(Foreign Key), sales Table Name: Region_4 Fields: Reg_ID(Primary Key), S_ID(Foreign Key), sales Query 1: Find out total of sales of each salesman in all the regions. Query 2: Find out total of sales of a particual salesman in all the regions. (if the first one is solved I think this will be easy. :-) )

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• BlackBerry - Multiple Screens or Single Screen with Content Manager?

  - by Max Gontar

  Hi! I've seen projects which use many screens each one for different layout and functionality. I've seen projects with only one screen (like wizard workflow) where content is changed on user interaction (and this seems to be logical to use single screen in wizards). But also I've seen projects (apps like game or messenger or phone settings utility) which use single screen for different functionalities. I can see such advantages of having single screen in app: keep same decoration design and menu or toolbar (which may be also achieved with inheritance) keep single screen in ui stack (which may be achieved by pop/push screen) easy to handle data over application Can you tell other advantages/disadvantages of single screen app? When its better to use this approach? Thank you!

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• c++ - what is faster ?

  - by VaioIsBorn

  If we have the following 2 snippets of code in c++ that do the same task: int a, b=somenumber; while(b > 0) { a = b % 3; b /= 3; } or int b=somenumber; while(b > 0) { int a=b%3; b /= 3; } I don't know much about computer architecture/c++ design, but i think that the first code is faster because it declares the integer a at the beginning and just uses it in the while-loop, and in the second code the integer a is being declared everytime the while-loop starts over. Can some one help me with this, am i correct or what and why ?

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• Refactoring FAT client legacy application

  - by Paul

  I am working on a fat client legacy C++ application which has a lot of business logic mixed in with the presentation side of things. I want to clean things out and refactor the code out completely, so there is a clear seperation of concerns. I am looking at MVC or some other suitable design pattern in order to achieve this. I would like to get recommendations from people who have walked this road before - Do I use MVP or MVC (or another pattern)? What is/are the best practices for undertaking something like this (i.e. useful steps/checks) ?

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• C++ Inheritance Question

  - by shaz

  I have a base class MessageHandler and 2 derived classes, MessageHandler_CB and MessageHandler_DQ. The derived classes redefine the handleMessage(...) method. MH_DQ processes a message and puts the result in a deque while MH_CB processes the message and then executes a callback function. The base class has a static callback function that I pass along with a this pointer to a library which calls the static callback when a new message is available for processing. My problem comes when I am in the static callback with a void * pointing to either a MH_DQ or a MH_CB. If I cast it to the base class the empty MessageHandler::handleMessage(...) method is called, rather than the version in the appropriate derived class. What is the best way to address this situation from a design perspective and/or what language features might help me to implement a solution to my problem? Thanks in advance!

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• values of diff keys to concatenate from a resource file, how?

  - by Narry

  I want to concatenate the values of two or more keys from a resource file, while assigning value to a control, somthing like <%$ Resources:LocalizedText, LeadTitle%" but, getting an error.Is it possible some way to concatenate the value of different keys from a resource file?

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• Need help on understanding Mobile First concept

  - by RhymeGuy

  So, I worked on responsive sites before but I'm on my way to build my first responsive site now. I opened some articles on the subject, and boom: Mobile First.. I have no idea how I skipped that concept till now. From the beginning I cant seem to understand whole thing (except that number of mobile devices will take out soon desktop computers) and here is why. How I'm supposed to know how my site will look for desktop version, if I design it for mobile first? I mean, on the smallest device I will have to eventually hide some content etc, how I'm supposed to know what to hide and move things, when I don't know how the site will look on bigger screen? Isn't stripping the things easier?!?! For me (right now), the Mobile First concept looks to me like building pyramid upside down.

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• Very basic database theory.

  - by John R

  I have a set of tables to show the relationship between organziations and supporters below. Although I have done some basic mySQL querries, I know very little about database 'design'. I plan to querry the database for: -a list of contributors to a specific organization... or, -a list of organizations that a specific suporter supports. The database tables for organiations and contributors may have other columns in the future and recieve a lesser amount of querries based on that information. A | X A | Y A | Z B | X B | Y C | X C | Z How should the tables be set up? I assume that there should be a third table, but there is still redundent information in the third table. Is there a better way of setting up the tables? +----+-------+ +-------------+----------+ +----+-------+ | id | org | | org | contr | | id | contr.| +----+-------+ +-------------+----------+ +----+-------+ | 1 | A | | 1 | 1 | | 1 | X | | 2 | B | | 1 | 2 | | 2 | Y | | 3 | C | | 1 | 3 | | 3 | Z | +----+-------+ | 2 | 1 | +----+-------+ | 2 | 2 | | 3 | 1 | | 3 | 3 | +-------------+----------+

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• Elegant ways of displaying a GridView with lots of columns (ASP.NET)

  - by Chris

  Hi, just a general design question that I'd like to hear some of your opinions on. I am designing a system for a client, and I'm using GridView' a lot. They need a lot of columns to be displayed in some of these, and I've had to resort to using a panel with a horizontal scrollbar. This presents some issues - keeping track of which row is which is difficult, even with alternating row colours, and it's generally pretty ugly. How have you dealt with these issues before? Are there any sort of AJAX controls that could help, so some data could be only displayed on hover or such? Or any other general ideas.

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• Normalization two types of customers into one table

  - by JDewzy

  I am trying to model a sales situation where you can sell to a person or to a business with a contact person. I cannot figure out the proper way to do this. It seems like 2 tables would be incorrect. But how do I model a Customer table that can be a business or a person? Would I just have a boolean for "business" and an additional "business_name" field that would default to Null. But then I have to do an if/then on the columns and that seems like poor design. Any advice, direction, or links is appreciated.

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• Single value data to multiple values of data in database relation

  - by Sofiane Merah

  I have such a hard time picturing this. I just don't have the brain to do it. I have a table called reports. --------------------------------------------- | report_id | set_of_bads | field1 | field2 | --------------------------------------------- | 123 | set1 | qwe | qwe | --------------------------------------------- | 321 | 123112 | ewq | ewq | --------------------------------------------- I have another table called bads. This table contains a list of bad data. ------------------------------------- | bad_id | set_it_belongs_to | field2 | field3 | ------------------------------------- | 1 | set1 | qwe | qwe | ------------------------------------- | 2 | set1 | qee | tte | ------------------------------------- | 3 | set1 | q44w | 3qwe | ------------------------------------- | 4 | 234 | qoow | 3qwe | ------------------------------------- Now I have set the first field of every table as the primary key. My question is, how do I connect the field set_of_bads to set_it_belongs_to in the bads table. This way if I want to get the entire set of data that is set1 by calling on the reports table I can do it. Example: hey reports table.. bring up the row that has the report_id 123. Okay thank you.. Now get all the rows from bads that has the set_of_bads value from the row with the report_id 123. Thanks.

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