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  • MYSQL Event to update another database table

    - by Lee
    Hey All, I have just taken over a project for a client and the database schema is in a total mess. I would like to rename a load of fields make it a relationship database. But doing this will be a painstaking process as they have an API running of it also. So the idea would be to create a new database and start re-writing the code to use this instead. But I need a way to keep these tables in sync during this process. Would you agree that I should use MYSQL EVENT's to keep updating the new table on Inserts / updates & deletes?? Or can you suggest a better way?? Hope you can advise !! thanks for any input I get

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  • How would you organize this Javascript?

    - by Anurag
    How do you usually organize complex web applications that are extremely rich on the client side. I have created a contrived example to indicate the kind of mess it's easy to get into if things are not managed well for big apps. Feel free to modify/extend this example as you wish - http://jsfiddle.net/NHyLC/1/ The example basically mirrors part of the comment posting on SO, and follows the following rules: Must have 15 characters minimum, after multiple spaces are trimmed out to one. If Add Comment is clicked, but the size is less than 15 after removing multiple spaces, then show a popup with the error. Indicate amount of characters remaining and summarize with color coding. Gray indicates a small comment, brown indicates a medium comment, orange a large comment, and red a comment overflow. One comment can only be submitted every 15 seconds. If comment is submitted too soon, show a popup with appropriate error message. A couple of issues I noticed with this example. This should ideally be a widget or some sort of packaged functionality. Things like a comment per 15 seconds, and minimum 15 character comment belong to some application wide policies rather than being embedded inside each widget. Too many hard-coded values. No code organization. Model, Views, Controllers are all bundled together. Not that MVC is the only approach for organizing rich client side web applications, but there is none in this example. How would you go about cleaning this up? Applying a little MVC/MVP along the way? Here's some of the relevant functions, but it will make more sense if you saw the entire code on jsfiddle: /** * Handle comment change. * Update character count. * Indicate progress */ function handleCommentUpdate(comment) { var status = $('.comment-status'); status.text(getStatusText(comment)); status.removeClass('mild spicy hot sizzling'); status.addClass(getStatusClass(comment)); } /** * Is the comment valid for submission */ function commentSubmittable(comment) { var notTooSoon = !isTooSoon(); var notEmpty = !isEmpty(comment); var hasEnoughCharacters = !isTooShort(comment); return notTooSoon && notEmpty && hasEnoughCharacters; } // submit comment $('.add-comment').click(function() { var comment = $('.comment-box').val(); // submit comment, fake ajax call if(commentSubmittable(comment)) { .. } // show a popup if comment is mostly spaces if(isTooShort(comment)) { if(comment.length < 15) { // blink status message } else { popup("Comment must be at least 15 characters in length."); } } // show a popup is comment submitted too soon else if(isTooSoon()) { popup("Only 1 comment allowed per 15 seconds."); } });

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  • do's and don'ts for writing mysql queries

    - by nik
    One thing I always wonder while writing query is that am I writing most optimized query or not? I know certain things like: 1) using SELECT field1, filed2 instead of SELECT * 2) Giving proper indexes to the tables but I am sure there are more things that should be kept in mind for writing queries, since most of the database can only grow more and optimal query will help gr8 in execution time, Can u share some tips and tricks on writing queries?

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  • Is there a Delphi dropdown notification component?

    - by Mason Wheeler
    You know how in Firefox, if something happens that requires your attention but isn't immediately urgent enough to require a modal dialog, it will drop down a little strip at the top of the tab with a question on it? I'd like to be able to put functionality like that in a Delphi app, but I don't know if there's a component for that. Does anyone know of one?

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  • Using HTTP Vary header to decide on a strategy to process a request

    - by Jacques René Mesrine
    I have a specific REST endpoint that creates a topic in a forum; but I want to apply different strategies when processing the request. e.g. If client A makes the call, perform moderation. if client B makes the call, do something else. The easiest would be to add a query param for differentiation: POST /resource?from=xyz Another brilliant idea is to use the Vary HTTP header. POST /resource Vary: xyz Any problems with this approach ?

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  • Modelling problem - Networked devices with commands

    - by Schneider
    I encountered a head scratching modelling problem today: We are modelling a physical control system composed of Devices and NetworkDevices. Any example of a Device is a TV. An example of a NetworkDevice is an IR transceiver with Ethernet connection. As you can see, to be able to control the TV over the internet we must connect the Device to the NetworkDevice. There is a one to many relationship between Device and NetworkDevice i.e. TV only has one NetworkDevice (the IR transceiver), but the IR transceiver may control many Devices (e.g. many TVs). So far no problem. The complicated bit is that every Device has a collection of Commands. The type of the Command (e.g IrCommand, SerialCommand - N.B. not currently modelled) depends on the type of NetworkDevice that the Device is connected to. In the current legacy system the Device has a collection of generic Commands (no typing) where fields are "interpreted" depending on the NetworkDevice type. How do I go about modelling this in OOP such that: You can only ever add a Command of the appropriate type, given the NetworkDevice the Device is attached to? If I change the NetworkDevice the Commands collection changes to the appropriate type Make it so the API is simple/elegant/intuitive to use

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  • Is it a good idea to cache data from web services into a database?

    - by Thierry Lam
    Let's assume that Stackoverflow offers web services where you can retrieve all the questions asked by a specific user. A request to get all question from user A can result in the following json output: { { "question": "What is rest?", "date_created": "20/02/2010", "votes": 1, }, { "question": "Which database to use for ...", "date_created": "20/07/2009", "votes": 5, }, } If I want to manipulate and present the data in any ways that I want, will it be wise to dump it in a local database? At some point, I will also want to retrieve all answers for each question and store them in a local database. The workflow that I'm thinking is: User logs in. Web services retrieve all questions asked by the logged in user, dump them in a local database. User wants all answers for a specific question, another web service does the retrieval and dump them in a local database. After user logs out, delete from the local database all questions and answers from that user.

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  • Data access pattern, combining push and pull?

    - by andlju
    I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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  • Anticipate factorial overflow

    - by Flavius
    Hi I'm wondering how I could anticipate that the next iteration will generate an integer overflow while calculating the factorial F. Let's say that at each iteration I have an int I and the maximum value is MAX_INT. It sounds like a homework, I know. It's not. It's just me asking myself "stupid" questions.

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  • algorithm || method to write prog

    - by fatai
    I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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  • Database Table of Boolean Values

    - by guazz
    What's the best method of storing a large number of booleans in a database table? Should I create a column for each boolean value or is there a more optimal method? Employee Table IsHardWorking IsEfficient IsCrazy IsOverworked IsUnderpaid ...etc.

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  • How strict to be when using Qt framework?

    - by toffeehoops
    I'm building a Qt application that needs to use libssh, a SSH client library. libssh (understandably) performs its own network connections, however Qt has its own infrastructure for network connections (QTcpSocket etc). Should I worry about these differences? Should I be trying to make libssh make network connections via QTcpSocket... Or if it works fine on the platforms I'm targeting, is that good enough?

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  • Database Modeling - Either/Or in Many-to-Many

    - by EkoostikMartin
    I have an either/or type of situation in a many-to-many relationship I'm trying to model. So I have these tables: Message ---- *MessageID MessageText Employee ---- *EmployeeID EmployeeName Team ---- *TeamID TeamName MessageTarget ---- MessageID EmployeeID (nullable) TeamID (nullable) So, a Message can have either a list of Employees, or a list of Teams as a MessageTarget. Is the MessageTarget table I have above the best way to implement this relationship? What constraints can I place on the MessageTarget effectively? How should I create a primary key on MessageTarget table?

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  • How do I correctly model data in SQL-based databases that have some columns in common, but also have

    - by Brandon Weiss
    For instance, let's say I have a User model. Users have things like logins, passwords, e-mail addresses, avatars, etc. But there are two types of Users that will be using this site, let's say Parents and Businesses. I need to store some different information for the Parents (e.g. childrens' names, domestic partner, salaries, etc.) than for the Businesses (e.g. industry, number of employees, etc.), but also some of it is the same, like logins and passwords. How do I correctly structure this in a SQL-based database? Thanks!

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  • Structuring Win32 GUI code

    - by kraf
    I wish to improve my code and file structure in larger Win32 projects with plenty of windows and controls. Currently, I tend to have one header and one source file for the entire implementation of a window or dialog. This works fine for small projects, but now it has come to the point where these implementations are starting to reach 1000-2000 lines, which is tedious to browse. A typical source file of mine looks like this: static LRESULT CALLBACK on_create(const HWND hwnd, WPARAM wp, LPARAM lp) { setup_menu(hwnd); setup_list(hwnd); setup_context_menu(hwnd); /* clip */ return 0; } static LRESULT CALLBACK on_notify(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { const NMHDR* header = (const NMHDR*)lp; /* At this point I feel that the control's event handlers doesn't * necessarily belong in the same source file. Perhaps I could move * each control's creation code and event handlers into a separate * source file? Good practice or cause of confusion? */ switch (header->idFrom) { case IDC_WINDOW_LIST: switch (header->code) { case NM_RCLICK: return on_window_list_right_click(hwnd, wp, lp); /* clip */ } } } static LRESULT CALLBACK wndmain_proc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) { switch (msg) { case WM_CREATE: return on_create(hwnd, wp, lp); case WM_CLOSE: return on_close(hwnd, wp, lp); case WM_NOTIFY: return on_notify(hwnd, wp, lp); /* It doesn't matter much how the window proc looks as it just forwards * events to the appropriate handler. */ /* clip */ default: return DefWindowProc(hwnd, msg, wp, lp); } } But now as the window has a lot more controls, and these controls in turn have their own message handlers, and then there's the menu click handlers, and so on... I'm getting lost, and I really need advice on how to structure this mess up in a good and sensible way. I have tried to find good open source examples of structuring Win32 code, but I just get more confused since there are hundreds of files, and within each of these files that seem GUI related, the Win32 GUI code seems so far encapsulated away. And when I finally find a CreateWindowEx statement, the window proc is nowhere to be found. Any advice on how to structure all the code while remaining sane would be greatly appreciated. Thanks! I don't wish to use any libraries or frameworks as I find the Win32 API interesting and valuable for learning. Any insight into how you structure your own GUI code could perhaps serve as inspiration.

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  • Multiple Tables or Multiple Schema

    - by Yan Cheng CHEOK
    http://stackoverflow.com/questions/1152405/postgresql-is-better-using-multiple-databases-with-1-schema-each-or-1-database I am new in schema concept for PostgreSQL. For the above mentioned scenario, I was wondering Why don't we use a single database (with default schema named public) Why don't we have a single table, to store multiple users row? Other tables which hold users related information, with foreign key point to the user table. Can anyone provide me a real case scenario, which single database, multiple schema will be extremely useful, and can't solve by conventional single database, single schema.

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  • Looking for some thoughts on an image printing app

    - by Alex
    Hey All, Im looking for thoughts/advice. I have an upcoming project (all .net) that will require the following: pulls data once a day from an online service provider based on certain criteria. saves data locally for reference and reporting the data thats pulled will be used to create gift cards. So after the data is loaded, a process will run to generate "virtual cards" and send them to a network printer. Once printed, the system will updated the local data recording a successful or failed print. My initial thought was to create a windows service to pull the data...but then I couldnt decide how I was going to put a "virtual card" together and get it to print. Then I considered doing it as a WPF app. I figure that will give me access to the graphics and printing ability. Maybe neither of these are the right direction....Any ideas or thoughts would be greatly appreciated. Alex

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  • Haskell: "how much" of a type should functions receive? and avoiding complete "reconstruction"

    - by L01man
    I've got these data types: data PointPlus = PointPlus { coords :: Point , velocity :: Vector } deriving (Eq) data BodyGeo = BodyGeo { pointPlus :: PointPlus , size :: Point } deriving (Eq) data Body = Body { geo :: BodyGeo , pict :: Color } deriving (Eq) It's the base datatype for characters, enemies, objects, etc. in my game (well, I just have two rectangles as the player and the ground right now :p). When a key, the characters moves right, left or jumps by changing its velocity. Moving is done by adding the velocity to the coords. Currently, it's written as follows: move (PointPlus (x, y) (xi, yi)) = PointPlus (x + xi, y + yi) (xi, yi) I'm just taking the PointPlus part of my Body and not the entire Body, otherwise it would be: move (Body (BodyGeo (PointPlus (x, y) (xi, yi)) wh) col) = (Body (BodyGeo (PointPlus (x + xi, y + yi) (xi, yi)) wh) col) Is the first version of move better? Anyway, if move only changes PointPlus, there must be another function that calls it inside a new Body. I explain: there's a function update which is called to update the game state; it is passed the current game state, a single Body for now, and returns the updated Body. update (Body (BodyGeo (PointPlus xy (xi, yi)) wh) pict) = (Body (BodyGeo (move (PointPlus xy (xi, yi))) wh) pict) That tickles me. Everything is kept the same within Body except the PointPlus. Is there a way to avoid this complete "reconstruction" by hand? Like in: update body = backInBody $ move $ pointPlus body Without having to define backInBody, of course.

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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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  • Is a "factory" method the right pattern?

    - by jdt141
    Hey all - So I'm working to improve an existing implementation. I have a number of polymorphic classes that are all composed into a higher level container class. The problem I'm dealing with at the moment is that the higher level container class, well, sucks. It looks something like this, which I really don't have a problem with (as the polymorphic classes in the container should be public). My real issue is the constructor... /* * class1 and class 2 derive from the same superclass */ class Container { public: boost::shared_ptr<ComposedClass1> class1; boost::shared_ptr<ComposedClass2> class2; private: ... } /* * Constructor - builds the objects that we need in this container. */ Container::Container(some params) { class1.reset(new ComposedClass1(...)); class2.reset(new ComposedClass2(...)); } What I really need is to make this container class more re-usable. By hard-coding up the member objects and instantiating them, it basically isn't and can only be used once. A factory is one way to build what I need (potentially by supplying a list of objects and their specific types to be created?) Other ways to get around this problem? Seems like someone should have solved it before... Thanks!

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  • Best practice for DAO pattern ?

    - by Tony
    I've seen a lot of codes use a service-dao pattern , I don't know the origin of this pattern . It force the front layer call service , then delegates some of the service task to dao. I want to ask : Does DAO layer do purely data access related task ? What about exception encapsulation ? Is there other pattern can be used to replace this ?

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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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