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  • Modeling a Generic Relationship in a Database

    - by StevenH
    This is most likely one for all you sexy DBAs out there: How would I effieciently model a relational database whereby I have a field in an "Event" table which defines a "SportType". This "SportsType" field can hold a link to different sports tables E.g. "FootballEvent", "RubgyEvent", "CricketEvent" and "F1 Event". Each of these Sports tables have different fields specific to that sport. My goal is to be able to genericly add sports types in the future as required, yet hold sport specific event data (fields) as part of my Event Entity. Is it possible to use an ORM such as NHibernate / Entity framework which would reflect such a relationship? I have thrown together a quick C# example to express my intent at a higher level: public class Event<T> where T : new() { public T Fields { get; set; } public Event() { EventType = new T(); } } public class FootballEvent { public Team CompetitorA { get; set; } public Team CompetitorB { get; set; } } public class TennisEvent { public Player CompetitorA { get; set; } public Player CompetitorB { get; set; } } public class F1RacingEvent { public List<Player> Drivers { get; set; } public List<Team> Teams { get; set; } } public class Team { public IEnumerable<Player> Squad { get; set; } } public class Player { public string Name { get; set; } public DateTime DOB { get; set;} }

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  • Suggest a Game Idea for my 3D World

    - by mrlinx
    Been creating a 3D complete world in OpenGL. For now, it features navigation like Google Earth, making possible the zooming from outter space to meter like level. My question is: How do you suggest I make this a fun and interesting game? My initial tought was to have a kind of moon lander where the user simply navigated the lander around the world. Anything better to suggest?

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  • One check constraint or multiple check constraints?

    - by RenderIn
    Any suggestions on whether fewer check constraints are better, or more? How should they be grouped if at all? Suppose I have 3 columns which are VARCHAR2(1 BYTE), each of which is a 'T'/'F' flag. I want to add a check constraint to each column specifying that only characters IN ('T', 'F') are allowed. Should I have 3 separate check constraints, one for each column: COL_1 IN ('T', 'F') COL_2 IN ('T', 'F') COL_3 IN ('T', 'F') Or a single check constraint: COL_1 IN ('T', 'F') AND COL_2 IN ('T', 'F') AND COL_3 IN ('T', 'F') My thoughts are it is best to keep these three separate, as the columns are logically unrelated to each other. The only case I would have a check constraint that examines more than one column is if there was some relationship between the value in one and the value in another, e.g.: (PARENT_CNT > 0 AND PRIMARY_PARENT IS NOT NULL) OR (PARENT_CNT = 0 AND PRIMARY_PARENT IS NULL)

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  • C# threading pattern that will let me flush

    - by Jeff Alexander
    I have a class that implements the Begin/End Invocation pattern where I initially used ThreadPool.QueueUserWorkItem() to do thread my work. I now have the side effect where someone using my class is calling the Begin (with callback) a ton of times to do a lot of processing so ThreadPool.QueueUserWorkItem is creating a ton of threads to do the processing. That in itself isn't bad but there are instances where they want to abandon the processing and start a new process but they are forced to wait for their first request to finish. Since ThreadPool.QueueUseWorkItem() doesn't allow me to cancel the threads I am trying to come up with a better way to queue up the work and maybe use an explicit FlushQueue() method in my class to allow the caller to abandon work in my queue. Anyone have any suggestion on a threading pattern that fits my needs?

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  • Reuse nib's across multiple UIViewControllers

    - by colm
    I've created some custom UITableViewCells in a nib file and would like to use that across multiple UIViewControllers. Can anyone tell me the best practice way to do that? My limited knowledge around loading nibs seems to suggest that you have to specify a single owner class in Interface Builder. Thanks.

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  • 7 Card Poker Hand Evaluator

    - by Peter
    Hey, Does anyone know a fast algorithm for evaluating 7 card poker hands? Something which is more efficient than simply brute-force checking a every 21 5-card combination of hands from a set of 7. Cheers, Pete

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  • algorithm diagram

    - by tunl
    This is the max searching algorithm diagram: So, I wonder how can draw diagram for Recursion in HaNoi Tower program: package tunl; public class TowersApp { static int n = 3; public static void main(String[] args) { TowersApp.doTowers(3, 'A', 'B', 'C'); } public static void doTowers(int n, char from, char inter, char to) { if (n == 1) { System.out.println("disk 1 from "+ from + " to " + to); } else { doTowers(n-1, from, to, inter); System.out.println("disk " + n + " from " + from + " to " + to); doTowers(n-1, inter, from, to); } } } I can't draw it. Anyone can help me !!!

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  • Building big, immutable objects without constructors having long parameter lists

    - by Malax
    Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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  • best way to store 1:1 user relationships in relational database

    - by aharon
    What is the best way to store user relationships, e.g. friendships, that must be bidirectional (you're my friend, thus I'm your friend) in a rel. database, e.g. MYSql? I can think of two ways: Everytime a user friends another user, I'd add two rows to a database, row A consisting of the user id of the innitiating user followed by the UID of the accepting user in the next column. Row B would be the reverse. You'd only add one row, UID(initiating user) followed by UID(accepting user); and then just search through both columns when trying to figure out whether user 1 is a friend of user 2. Surely there is something better?

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  • 3rd party data - Store in Data Warehouse or Primary database?

    - by brydgesk
    This is mostly a data warehouse philosophy question. My project involves an Oracle forms application, and a Teradata Data Warehouse for reporting and ad-hoc purposes. In addition to the primary data created by the users of our application, we also require data from various other sources. Currently, this 3rd party data comes via FTPd flat files directly to our Data Warehouse. To access the data, our users must use a series of custom BusinessObjects reports. My question is, would it make more sense for this data to be sent to our source Oracle system instead? Is it ever appropriate for a Data Warehouse to be the point of origin for users to access raw data? In short, is it more important that the operational database contain only the data created by your project, or that the data warehouse remain dedicated solely to reporting and analysis?

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  • How to add an "Export to ebook" feature to a site?

    - by systempuntoout
    How could i add to a blog or site in general a feature that let users export the content to epub format or some other open ebook formats? It's not a feature that i normally see on most of the site i browse every day (some has export to pdf that is not great as ebook format), do you think it is feasible? I own an ebook reader and reading saved html to pdf pages is not so good. I'm searching for a general solution here so i have not specified any specific technology; if you have some sites that offer this feature i would like to try them. thanks

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  • Loose Coupling vs. Information Hiding and Ease of Change

    - by cretzel
    I'm just reading Code Complete by Steve McConell and I'm thinking of an Example he gives in a section about loose coupling. It's about the interface of a method that calculates the number of holidays for an employee, which is calculated from the entry date of the employee and her sales. The author suggests a to have entry date and sales as the parameters of the method instead of an instance of the employee: int holidays(Date entryDate, Number sales) instead of int holidays(Employee emp) The argument is that this decouples the client of the method because it does not need to know anything about the Employee class. Two things came to my mind: Providing all the parameters that are needed for the calculation breaks encapsulation. It shows the internals of the method on how it computes the result. It's harder to change, e.g. when someone decides that also the age of the employee should be included in the calculation. One would have to change the signature. What's your opinion?

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  • When writing a game, should you make objects/enemies/etc. have unique ID numbers?

    - by SLC
    I have recently encountered some issues with merely passing references to objects/enemies in a game I am making, and am wondering if I am using the wrong approach. The main issue I have is disposing of enemies and objects, when other enemies or players may still have links to them. For example, if you have a Rabbit, and a Wolf, the Wolf may have selected the Rabbit to be its target. What I am doing, is the wolf has a GameObject Target = null; and when it decides it is hungry, the Target becomes the Rabbit. If the Rabbit then dies, such as another wolf killing it, it cannot be removed from the game properly because this wolf still has a reference to it. In addition, if you are using a decoupled approach, the rabbit could hit by lightning, reducing its health to below zero. When it next updates itself, it realises it has died, and is removed from the game... but there is no way to update everything that is interested in it. If you gave every enemy a unique ID, you could simply use references to that instead, and use a central lookup class that handled it. If the monster died, the lookup class could remove it from its own index, and subsequently anything trying to access it would be informed that it's dead, and then they could act accordingly. Any thoughts on this?

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  • mysql unique-constraint

    - by Cypher
    I have two tables -- Variables (id, name) and Variable_Entries (id, var_id, value). I want each variable to have a unique set of entries. If I make the value entry unique then a different variable won't be able to have that same value which is not right. Is there some way to make the value column unique for identical var_id's?

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  • database splitting; multiple tables

    - by Ben
    I am coding a classifieds ad web app. What is the optimal way to structure the database for this? Because of the high repeatability, would it be faster (in terms of searching/indexing) to have a separate table in the database for each city? Or would it be okay to just have one table for every city (it would have a lot of rows..). The classifieds table has id, user_id, city_name, category,[description and detail fields].

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  • Proper way to set class variables

    - by ensnare
    I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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  • Access Error when running windows program

    - by JPJedi
    I have a windows form application that uses microsoft access for the database on the backend. When I run that application I get an error that says access is not installed on the computer. I thought that if I included the reference that it will be included with what I release so the user would not have to have access installed. How do I include the Access Runtime to be distributed/installed when my application is installed?

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  • Best method to store Enum in Database

    - by LnDCobra
    What is the best method of storing an Enum in a Database using C# And Visual Studio and MySQL Data Connector. I am going to be creating a new project with over 100 Enums, and majority of them will have to be stored in the database. Creating converters for each one would be a long winded process therefore I'm wondering if visual studio or someone has any methods for this that I haven't heard off.

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  • MVC implementation/best-practices question

    - by Vivin Paliath
    I have to work with some code that isn't truly MVC (i.e., it doesn't use an explicit framework among other things). Right now we make do with servlets that pass data to services. Here is my problem. I am receiving a post to a servlet that contains a whole bunch of address data that I have to save to the database. The data is (obviously) in the HttpRequest object. My question is, how do I pass this data into a service? I am reluctant to do it like this: AddressService.saveAddress(request); Because I don't think the service should have a dependency on the request. My other option is to do something like this: String addressLine = request.getParameter("addressLine"); .. .. about 7 other parameters .. String zip = request.getParameter("zip"); AddressService.saveAddress(addressLine, ... 7 other parameters ..., zip); But I don't like having a function with a huge number of parameters either. I was thinking of making an intermediate object called AddressData that would hold data from the request, and then passing that into the service. Is that an acceptable way of doing things?

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  • Object database for website

    - by Damian
    I was planning to use db4o for a website. It's a microblog site with small posts and comments developed in java. The thing is I contacted db4o support asking if db4o would be suitable for a website, and they answered me that only for websites with low concurrency. That means with few requests? So, now I think db4o will not be a good choice. Do you know if there is any object database for java suitable for a website?

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  • Is it possible to create a quine in every turing-complete language?

    - by sub
    I just wanted to know if it is 100% possible, if my language is turing-complete, to write a program in it that prints itself out (of course not using a file reading function) So if the language just has the really necessary things in order to make it turing complete (I would prove that by translating Brainf*ck code to it), like output, variables, conditions and gotos (hell yes, gotos), can I try writing a quine in it? I'm also asking this because I'm not sure that a quine directly fits into Turing's law that the turing machine is capable of any computational task. I just want to know so I don't try for years without knowing that it may be impossible.

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