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  • how relate one table to another for future records

    - by Sinan
    I have a games table which holds the data about a game. Then another table which holds the data about news. So far so good. First I thought about creating a junction table for game_news so I could relate news to games. This way works as intended when the game exists. So whenever I insert a news I can relate it to a game using the junction table. However there are cases when there is news about game but the game isn't published and it doesn't exists. So my question would be; is there a way to relate these news to a particular game when the game record is created. What is the best way to do this? Any ideas?

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  • Entity framework (1): implement 1 foreign key to multiple tables

    - by Michel
    Hi, i've modeled this: i have an import table, and an import steps table import 1 .. N importsteps Now i have a table importparams, which hold key/value pairs to register all kind of info about the import or the importsteps. So i have modeled a FK in SqlServer which points to the PK of the import table and to the PK of the importsteps table (the ID's for both the import as the importsteps table are guids, so i can query the importparams with either the id from import or from importsteps and get the right importparams). Makes sense a bit? But how can i model this in the EF? I can see it's a bit hard for the EF to model this, because one realtion can point to multiple classes, but is there a way? The workaround normally is just to get all importparams where FK is the ID, but as you know the FK is not available in the EF version 1. I hope you can help me out, michel

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  • Database access through collections

    - by Mike
    Hi All, I have an 3 tiered application where I need to get database results and populated the UI. I have a MessagesCollection class that deals with messages. I load my user from the database. On the instantiation of a user (ie. new User()), a MessageCollection Messages = new MessageCollection(this) is performed. Message collection accepts a user as a parameter. User user = user.LoadUser("bob"); I want to get the messages for Bob. user.Messages.GetUnreadMessages(); GetUnreadMessages calls my Business Data provider which in turn calls the data access layer. The Business data provider returns List. My question is - I am not sure what the best practice is here - If I have a collection of messages in an array inside the MessagesCollection class, I could implement ICollection to provide GetEnumerator() and ability to traverse the messages. But what happens if the messages change and the the user has old messages loaded? What about big message collections? What if my user had 10,000 unread messages? I don't think accessing the database and returning 10,000 Message objects would be efficient.

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  • Best way to store sales tax information

    - by Seph
    When designing a stock management database system (sales / purchases) what would be the best way to store the various taxes and other such amounts? A few of the fields that could be saved are: Unit price excluding tax Unit price including tax Tax per item Total excluding tax (rounded to 2 decimals) Total including tax (rounded to 2 decimals) Total tax (rounded to 2 decimals) Currently the most reasonable solution so far is storing down (roughly) item, quantity, total excluding tax (rounded) and the total tax (rounded). Can anyone suggest some better way of storing this details for a generic system? Also, given the system needs to be robust, what should be done if there were multiple tax values (eg: state and city) which might need to be separated, in this case a separate table would be in order, but would it be considered excessive to just have a rowID and some taxID mapping to a totalTax column?

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  • Function overloading by return type?

    - by dsimcha
    Why don't more mainstream statically typed languages support function/method overloading by return type? I can't think of any that do. It seems no less useful or reasonable than supporting overload by parameter type. How come it's so much less popular?

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  • Discover periodic patterns in a large data-set

    - by Miner
    I have a large sequence of tuples on disk in the form (t1, k1) (t2, k2) ... (tn, kn) ti is a monotonically increasing timestamp and ki is a key (assume a fixed length string if needed). Neither ti nor ki are guaranteed to be unique. However, the number of unique tis and kis is huge (millions). n itself is very large (100 Million+) and the size of k (approx 500 bytes) makes it impossible to store everything in memory. I would like to find out periodic occurrences of keys in this sequence. For example, if I have the sequence (1, a) (2, b) (3, c) (4, b) (5, a) (6, b) (7, d) (8, b) (9, a) (10, b) The algorithm should emit (a, 4) and (b, 2). That is a occurs with a period of 4 and b occurs with a period of 2. If I build a hash of all keys and store the average of the difference between consecutive timestamps of each key and a std deviation of the same, I might be able to make a pass, and report only the ones that have an acceptable std deviation(ideally, 0). However, it requires one bucket per unique key, whereas in practice, I might have very few really periodic patterns. Any better ways?

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  • Model login constraints based on time

    - by DaDaDom
    Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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  • Testing chess game

    - by mousey
    There is a software for chess game and we need to test the following method: boolean canMoveTo(int x, int y) x and y are the coordinates of the chess board and it returns true/false whether the piece can move to that position or not. We need to test this method for a pawn piece and you can set up the board any way you like prior to running a test case. Source code is not provided

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  • How to designing a generic databse whos layout may change over time?

    - by mawg
    Here's a tricky one - how do I programatically create and interrogate a database who's contents I can't really foresee? I am implementing a generic input form system. The user can create PHP forms with a WYSIWYG layout and use them for any purpose he wishes. He can also query the input. So, we have three stages: a form is designed and generated. This is a one-off procedure, although the form can be edited later. This designs the database. someone or several people make use of the form - say for daily sales reports, stock keeping, payroll, etc. Their input to the forms is written to the database. others, maybe management, can query the database and generate reports. Since these forms are generic, I can't predict the database structure - other than to say that it will reflect HTML form fields and consist of a the data input from collection of edit boxes, memos, radio buttons and the like. Questions and remarks: A) how can I best structure the database, in terms of tables and columns? What about primary keys? My first thought was to use the control name to identify each column, then I realized that the user can edit the form and rename, so that maybe "name" becomes "employee" or "wages" becomes ":salary". I am leaning towards a unique number for each. B) how best to key the rows? I was thinking of a timestamp to allow me to query and a column for the row Id from A) C) I have to handle column rename/insert/delete. Foe deletion, I am unsure whether to delete the data from the database. Even if the user is not inputting it from the form any more he may wish to query what was previously entered. Or there may be some legal requirements to retain the data. Any gotchas in column rename/insert/delete? D) For the querying, I can have my PHP interrogate the database to get column names and generate a form with a list where each entry has a database column name, a checkbox to say if it should be used in the query and, based on column type, some selection criteria. That ought to be enough to build searches like "position = 'senior salesman' and salary 50k". E) I probably have to generate some fancy charts - graphs, histograms, pie charts, etc for query results of numerical data over time. I need to find some good FOSS PHP for this. F) What else have I forgotten? This all seems very tricky to me, but I am database n00b - maybe it is simple to you gurus?

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  • Why are alloc and init called separately in Objective-C?

    - by André Hoffmann
    Note: I'm relatively new to Objective-C and am coming from Java and PHP. Could someone explain to me why I always have to first allocate and then initialize an instance? Couldn't this be done in the init methods like this: + (MyClass*)init { MyClass *instance = [MyClass alloc]; [instance setFoo:@"bla"]; return instance; } + (MyClass*)initWithString:(NSString*)text { MyClass *instance = [MyClass init]; [instance setFoo:text]; return instance; } ... Is this just a relict from the old C days or is there something that I'm not seeing? I know this isn't a problem as I could as well always call alloc and init, but since it's a bit tedious I'd like to at least know why I'm doing it. I'm liking the expressiveness of the language so far, but this is something that I want to fully understand in order to think the Objective-C way. Thank you!

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  • Java Polymorphism - Selecting correct method based on subtype

    - by Marty Pitt
    Hi Given the following Class and Service layer signatures: public class PersonActionRequest { PersonVO person // ... other fields } public class MyServiceLayerClass { public void requestAction(PersonActionRequest request) { PersonVO abstractPerson = request.getPerson(); // call appropriate executeAction method based on subclass of PersonVO } private void executeAction(PersonVO person) {} private void executeAction(EmployeeVO employee) {} private void executeAction(ManagerVO manager) {} private void executeAction(UnicornWranglerVO unicornWrangler) {} } As discussed here, java will select the best method based on type info at compile time. (Ie., it will always select executeAction(PersonVO person) ). What's the most appropriate way to select the correct method? The internet tells me that using instanceof gets me slapped. However, I don't see the appropraite way to select the method without explictly casting abstractPerson to one of the other concrete types. Thanks Marty

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  • How my Website looks like under Different Screen Resolutions?

    - by strakastroukas
    Back in the past, i found a third party webpage that was able to capture and save images of my website in different resolutions and browsers. Of course i have no more that bookmark... So is there any webpage or application where i can see how my webpage looks like in different resolution? And here are the resolutions i would like to check for... 1. 1024x768 24.56% 2. 1280x800 22.06% 3. 1280x1024 13.42% 4. 1366x768 7.10% 5. 1440x900 6.68%

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  • Subversion Repository Layout

    - by Tim Long
    Most subversion tools create a default repository layout with /trunk, /branches and /tags. The documentation also recommends not using separate repositories for each project, so that code can be more easily shared. Following that advice has led to me having a repository with the following layout: /trunk /Project1 /Project2 /branches /Project1 /Project2 /tags /Project1 /Project2 and so on, you get the idea. Over time, I've found this structure a bit clumsy and it occurred to me that there's an alternative interpretation of the recommendations, such as: /Project1 /trunk /branches /tags /Project2 /trunk /branches /tags So, which layout do people use, and why? Or - is there another way to do things that I've completely missed?

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  • Displaying an NSString on a Custom View

    - by ilovetacos
    I have an interface that has an NSTextField, NSButton, and an NSView. When I type something in the textfield and press the button, I want the text to be drawn in the NSView. So far I have everything connected and working, except for the view. How can I connect the text and the view so that every time I press the button, the text is drawn to the view?

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  • Format for storing contacts in a database

    - by Gart
    I'm thinking of the best way to store personal contacts in a database for a business application. The traditional and straightforward approach would be to create a table with columns for each element, i.e. Name, Telephone Number, Job title, Address, etc... However, there are known industry standards for this kind of data, like for example vCard, or hCard, or vCard-RDF/XML or even Windows Contacts XML Schema. Utilizing an standard format would offer some benefits, like inter-operablilty with other systems. But how can I decide which method to use? The requirements are mainly to store the data. Search and ordering queries are highly unlikely but possible. The volume of the data is 100,000 records at maximum. My database engine supports native XML columns. I have been thinking to use some XML-based format to store the personal contacts. Then it will be possible to utilize XML indexes on this data, if searching and ordering is needed. Is this a good approach? Which contacts format and schema would you recommend for this?

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  • How to perform a literal match with regex using wildcard

    - by kashif4u
    I am trying to perform literal match with regular expression using wildcard. string utterance = "Show me customer id 19"; string pattern 1 = "*tom*"; string patter 2 = "*customer id [0-9]*"; Desired results: if (Regex.IsMatch(utterance, pattern 1 )) { MATCH NOT FOUND } if (Regex.IsMatch(utterance, pattern 2 )) { MATCH FOUND } I have tried looking for literal match solution/syntax in wildcard but having difficulty. Could you also enlighten me with with an example on possible Pattern Matching Strength algorithm i.e. if code match 90 select? Note: I have table with 100000 records to perform literal matches from user utterances. Thanks in advance.

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  • Modifying my website to allow anonymous comments

    - by David
    I write the code for my own website as an educational/fun exercise. Right now part of the website is a blog (like every other site out there :-/) which supports the usual basic blog features, including commenting on posts. But I only have comments enabled for logged-in users; I want to alter the code to allow anonymous comments - that is, I want to allow people to post comments without first creating a user account on my site, although there will still be some sort of authentication involved to prevent spam. Question: what information should I save for anonymous comments? I'm thinking at least display name and email address (for displaying a Gravatar), and probably website URL because I eventually want to accept OpenID as well, but would anything else make sense? Other question: how should I modify the database to store this information? The schema I have for the comment table is currently comment_id smallint(5) // The unique comment ID post_id smallint(5) // The ID of the post the comment was made on user_id smallint(5) // The ID of the user account who made the comment comment_subject varchar(128) comment_date timestamp comment_text text Should I add additional fields for name, email address, etc. to the comment table? (seems like a bad idea) Create a new "anonymous users" table? (and if so, how to keep anonymous user ids from conflicting with regular user ids) Or create fake user accounts for anonymous users in my existing users table? Part of what's making this tricky is that if someone tries to post an anonymous comment using an email address (or OpenID) that's already associated with an account on my site, I'd like to catch that and prompt them to log in.

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  • Should a developer be a designer?

    - by nepb
    I have been developing websites for quite some time and I am not so good in designing websites? My Boss is refering me to take some lessons on it. But I really want to stick to development rather than designing?

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  • How To Implement The Query Side Of CQS in DDD?

    - by Laz
    I have implemented the command side of DDD using the domain model and repositories, but how do I implement the query side? Do I create an entirely new domain model for the UI, and where is this kept in the project structure...in the domain layer, the UI layer, etc? Also, what do I use as my querying mechanism, do I create new repositories specifically for the UI domain objects, something other than repositories, or something else?

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  • Best Practice for Utilities Class?

    - by Sonny Boy
    Hey all, We currently have a utilities class that handles a lot of string formatting, date displays, and similar functionality and it's a shared/static class. Is this the "correct" way of doing things or should we be instanciating the utility class as and when we need it? Our main goal here is to reduce memory footprint but performance of the application is also a consideration. Thanks, Matt PS. We're using .NET 2.0

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  • Avoiding Duplicate Data in DB (for use with Rails)

    - by ants
    I have five tables that I am trying to get to work nicely together but may need some help. I have three main tables: accounts members and roles. With two join tables account_members and account_member_roles. The accounts and members table are joined by account_members (fk account_id and member_id) table. The other 2 tables are the problem (roles and account_member_roles). A member of an account can have more than one role and I have the account_member_roles (fk account_member_id and role_id) table joining the account_members join table and the roles table. That seems logical but can you have a relationship with a join table? What I'd like to be able to do is when creaeting an account, for instance, I would like @account.save to include the roles and update the account_member_roles table neatly ..... but through the account_members join table. I've tried ..... accept_nested_attributes_for :members, :account_member_roles in the account.rb but I get ..... ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection (Cannot modify association 'Account#account_member_roles' because the source reflection class 'AccountMemberRole' is associated to 'AccountMember' via :has_many.) upon trying to save a record. Any advice on how I should approach this? CIA -ants

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  • What is the best approach to binding commands in a ViewModel to elements in the View?

    - by Micah
    Anyone who has tried to implement RoutedCommands in WPF using M-V-VM has undoubtedly run into issues. Commands (non-UI commands that is) should be implemented in the ViewModel. For instance if I needed to save a CustomerViewModel then I would implement that as a command directly on my CustomerViewModel. However if I wanted to pop up a window to show the users addresses I would implement a ShowCustomerAddress command directly in the view since this a UI specific function. How do I define the command bindings in the viewmodel, and use them in the view?

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