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  • What resources will help me understand the fundamentals of Relational Database Design.

    - by Rachel
    This are few of the fundamental database questions which has always given me trouble. I have tried using google and wiki but I somehow I miss out on understanding the functionality rather than terminology. If possible would really appreciate if someone can share more insights on this questions using some visual representative examples. What is a key? A candidate key? A primary key? An alternate key? A foreign key? What is an index and how does it help your database? What are the data types available and when to use which ones?

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  • Design review - do you think I'm doing this the right way? First commercial project for me!

    - by Sergio Tapia
    I'm tasked with designing an application that will allow a person to scan a legal document, save that associated with a Name and save it to a database. Now, inside of the Organization, there are many departments, and each department can have many sub departments. Problem lies in that some larger organizations will have many departments and smallers ones will only have 1 or two. I've though about creating a Department table and a Supdepartment table to create associations, etc. That way it's extensible and users can dynamically create departments to fit my program to their organizational scheme. Am I approaching this the right way? As I said, this is my first commercial application so I want to do it right and set a name for myself for delivering things on time and good code for other to expand upon.

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  • UX Design Question: Should a multi step wizard save the form contents when the user clicks 'go back'

    - by Ashwin Prabhu
    I am developing a web application that collects data over multiple steps through a wizard. Steps are generally not interdependent, in that data input at each step has little or no effect on the consequent steps. However each step may have a set of validations which determine whether the user can progress to the next step by clicking 'continue' What should be the behavior when the user clicks previous? a Quickly move to the previous page, thus losing all the unsaved data in the form. Prompting the user with a warning is an option, but it can become irritating quite soon. b Move to the previous page saving all the data in the current step - without triggering validations, so that when the user comes back she sees the form in the same state that she left it in. c any other behaviour All opinions are welcome :)

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  • PHP OOP Design Patterns: Should I Create two seperate classes for registration and form validation?

    - by Joshua Poshua
    So here's my problem: I have two types of registration, registration A and registration B, each will have some of the same fields and some different fields. I was going to create abstract class registration and both A and B would have their own classes that extend from registration. My question is, should I create a seperate Validation class with seperate A and B validation classes that extend? or is there a better pattern to use for something like this? Thanks

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  • Database table design vs. ease of use.

    - by Gastoni
    I have a table with 3 fields: color, fruit, date. I can pick 1 fruit and 1 color, but I can do this only once each day. examples: red, apple, monday red, mango, monday blue, apple, monday blue, mango, monday red, apple, tuesday The two ways in which I could build the table are: 1.- To have color, fruit and date be a composite primary key (PK). This makes it easy to insert data into the table because all the validation needed is done by the database. PK color PK fruit PK date 2.- Have and id column set as PK and then all the other fields. Many say thats the way it should be, because composite PKs are evil. For example, CakePHP does no support them. PK id color fruit date Both have advantages. Which would be the 'better' approach?

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  • c++ Design pattern for CoW, inherited classes, and variable shared data?

    - by krunk
    I've designed a copy-on-write base class. The class holds the default set of data needed by all children in a shared data model/CoW model. The derived classes also have data that only pertains to them, but should be CoW between other instances of that derived class. I'm looking for a clean way to implement this. If I had a base class FooInterface with shared data FooDataPrivate and a derived object FooDerived. I could create a FooDerivedDataPrivate. The underlying data structure would not effect the exposed getters/setters API, so it's not about how a user interfaces with the objects. I'm just wondering if this is a typical MO for such cases or if there's a better/cleaner way? What peeks my interest, is I see the potential of inheritance between the the private data classes. E.g. FooDerivedDataPrivate : public FooDataPrivate, but I'm not seeing a way to take advantage of that polymorphism in my derived classes. class FooDataPrivate { public: Ref ref; // atomic reference counting object int a; int b; int c; }; class FooInterface { public: // constructors and such // .... // methods are implemented to be copy on write. void setA(int val); void setB(int val); void setC(int val); // copy constructors, destructors, etc. all CoW friendly private: FooDataPrivate *data; }; class FooDerived : public FooInterface { public: FooDerived() : FooInterface() {} private: // need more shared data for FooDerived // this is the ???, how is this best done cleanly? };

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  • Should I design the application or model (database) first?

    - by YonahW
    I am getting ready to start building a new web project in my spare time to bring to fruition an idea that has been bouncing around my head for a while. I have never gotten down whether I am better off first building the model and then the consuming application or the other way around. What are the best practices? What would you build first and why? I imagine that in general the application should generally drive the model, however the application like many websites really doesn't do much without the model. For some reason I find it easier at times to think in terms of the model since the application is really just actions on the model. Is this a poor way of thinking about things? What advantages/disadvantages does each option have?

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  • True or False: Good design calls for every table to have a primary key, if nothing else, a running i

    - by Velika
    Consider a grocery store scenario (I'm making this up) where you have FACT records that represent a sale transaction, where the columns of the Fact table include SaleItemFact Table ------------------ CustomerID ProductID Price DistributorID DateOfSale Etc Etc Etc Even if there are duplicates in the table when you consider ALL the keys, I would contend that a surrogate running numeric key (i.e. identity column) should be made up, e.g., TransactionNumber of type Integer. I can see someone arguing that a Fact table might not have a unique key (though I'd invent one and waste the 4 bytes, but how about a dimension table?

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  • Which design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English. EDITED - Asking for multiple patterns.

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  • How to design a command line program reusable for a future development of a GUI?

    - by systempuntoout
    What are some best practices to keep in mind when developing a script program that could be integrated with a GUI, probably by somebody else, in the future? Possible scenario: i develop a fancy python CLI program that scrapes every unicorn images from the web i decide to publish it on github a unicorn fan programmer decides to take the sources and build a GUI on them. he\she gives up because my code is not reusable How do i avoid step four and let unicorn fan programmer build his\her GUI without hassle?

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  • What is the best Design/Way to keep user connected ?

    - by Fasih Hansmukh
    Am working on a POC for self learning in which I want to keep my user connected in LIVE pattern. For example, A game in which 4 user can play at a time , here I need to keep this user connected to my game . M not good at Socket type of programming and love to do that in Services way.What i wana know is 'What is the best way of doing this'. According to my initial Brain Storming, I have decided that I will use SilverLight(In Browser Or Out of Browser) as Front end [I have no issue in that]. I m more concern in back end. Either I make an handler or make a WCF service or use full duplex service and use pooling mechanism for that. As a random thought I come up with a Timer type logic that will fire every after 10 seconds at clients end and get status like Is it now Its turn to roll a dice Home many user left (in case if some of them left) What are connected user status in game like there score/points ect and update game view according to this at his end Kindly place your best answers here that will help me to learn this. Regards and thanks in Advance EDIT: Starting Bounty as i need more feedback. FH

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  • What design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English.

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  • Quality Design for Asynchronous WCF Services Calls in a Middle-Tier and Returning Data to UI Tier

    - by Perplexed
    I have a WPF application with a group of asynchronous WCF service calls all mashed into the code behind, complete with event handlers and everything, that I have to refactor to productionize and maintain. I want to separate concerns here for maintainability and all the other good reasons to do this, but I'm not sure exactly how to achieve this. Anybody have any good ideas on how to do this, or at least some links to put me in the right direction? My thinking: Create an "infrastructure" layer and reference the services there. Move the asynchronous event handlers into this layer. When an update is called, I will bubble up my own event with my own derivation of the EventArgs class that contains the data the UI will need. I'll have a fairly coupled hooking of the UI to the infrastructure layer as it will consume events I fire off upon completion of an asynchronous data call.

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  • Algorithm design: can you provide a solution to the multiple knapsack problem?

    - by MalcomTucker
    I am looking for a pseudo-code solution to what is effectively the Multiple Knapsack Problem (optimisation statement is halfway down the page). I think this problem is NP Complete so the solution doesn't need to be optimal, rather if it is fairly efficient and easily implemented that would be good. The problem is this: I have many work items, with each taking a different (but fixed and known) amount of time to complete. I need to divide these work items into groups so as to have the smallest number of groups (ideally), with each group of work items taking no longer than a given total threshold - say 1 hour. I am flexible about the threshold - it doesnt need to be rigidly applied, though should be close. My idea was to allocate work items into bins where each bin represents 90% of the threshold, 80%, 70% and so on. I could then match items that take 90% to those that take 10%, and so on. Any better ideas?

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  • Icons: How does a developer with no design skill make his/her application icons look pretty?

    - by Martin
    I probably spend far too much time trying to make my visual interfaces look good, and while I'm pretty adept at finding the right match between usability and style one area I am hopeless at is making nice looking icons. How do you people overcome this (I'm sure common) problem? I'm thinking of things like images on buttons and perhaps most important of all, the actual application icon. Do you rely on third party designers, in or out of house? Or do you know of some hidden website that offers lots of icons for us to use? I've tried Google but I seem to find either expensive packages that are very specific, millions of Star Trek icons or icons that look abysmal at 16x16 which is my preferred size on in-application buttons. Any help/advice appreciated.

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  • Please suggest me the best way to design my database.

    - by Raymond Ho
    I have a table named "Pages" and a table named "Categories". Each entry of the table "Pages" is linked to the table "Categories". The "Categories" table have 5 entries, they are: "Car", "Websites", "Technology", "Mobile Phones", and "Interest". So each time I put an entry to the "Pages" table, I need to map it to the "Categories" table so are arranged properly. Here's my table: Pages ______ id [PK] name url Categories ______ id [PK] Categoryname Pages2Categories ______ Pages.id Categories.id So my question is, is this the most efficient way to create this kind of relationships between tables? It seems very amateur

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  • Database design (MySql)::should we put html data in text field inside database table or more efficie

    - by meyosef
    Hi, We building big Web Application and we use mysql, we want to make mysql database more fast. Some of us think if we will put message html body inside table and not inside text.txt in will make database heavy and not fast. Thanks, *Part of main table that hold message: option 1:hold html message body inside database message { id (int) subject (varchar) body (text) } option 2: hold html message body inside body1.txt file message { id (int) subject (varchar) file_body_path (varchar) } *

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  • Having to insert a record, then update the same record warrants 1:1 relationship design?

    - by dianovich
    Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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  • database design: table with large amount of columns (50+) or many sub tables with small amount of co

    - by Guillaume
    In our oroject we already have a lots of tables (100+). Some of them contains a lot of columns (50-100) and we are facing the need of adding more columns from time to time. What do you think is best - from maintenance and performance point of view - to split these huge tables in smaller entities or to keep the tables the way they are ? We are using an ORM tools, so we don't need to write custom request.

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