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  • How to overcome shortcomings in reporting from EAV database?

    - by David Archer
    The major shortcomings with Entity-Attribute-Value database designs in SQL all seem to be related to being able to query and report on the data efficiently and quickly. Most of the information I read on the subject warn against implementing EAV due to these problems and the commonality of querying/reporting for almost all applications. I am currently designing a system where almost all the fields necessary for data storage are not known at design/compile time and are defined by the end-user of the system. EAV seems like a good fit for this requirement but due to the problems I've read about, I am hesitant in implementing it as there are also some pretty heavy reporting requirements for this system as well. I think I've come up with a way around this but would like to pose the question to the SO community. Given that typical normalized database (OLTP) still isn't always the best option for running reports, a good practice seems to be having a "reporting" database (OLAP) where the data from the normalized database is copied to, indexed extensively, and possibly denormalized for easier querying. Could the same idea be used to work around the shortcomings of an EAV design? The main downside I see are the increased complexity of transferring the data from the EAV database to reporting as you may end up having to alter the tables in the reporting database as new fields are defined in the EAV database. But that is hardly impossible and seems to be an acceptable tradeoff for the increased flexibility given by the EAV design. This downside also exists if I use a non-SQL data store (i.e. CouchDB or similar) for the main data storage since all the standard reporting tools are expecting a SQL backend to query against. Do the issues with EAV systems mostly go away if you have a seperate reporting database for querying? EDIT: Thanks for the comments so far. One of the important things about the system I'm working on it that I'm really only talking about using EAV for one of the entities, not everything in the system. The whole gist of the system is to be able to pull data from multiple disparate sources that are not known ahead of time and crunch the data to come up with some "best known" data about a particular entity. So every "field" I'm dealing with is multi-valued and I'm also required to track history for each. The normalized design for this ends up being 1 table per field which makes querying it kind of painful anyway. Here are the table schemas and sample data I'm looking at (obviously changed from what I'm working on but I think it illustrates the point well): EAV Tables Person ------------------- - Id - Name - ------------------- - 123 - Joe Smith - ------------------- Person_Value ------------------------------------------------------------------- - PersonId - Source - Field - Value - EffectiveDate - ------------------------------------------------------------------- - 123 - CIA - HomeAddress - 123 Cherry Ln - 2010-03-26 - - 123 - DMV - HomeAddress - 561 Stoney Rd - 2010-02-15 - - 123 - FBI - HomeAddress - 676 Lancas Dr - 2010-03-01 - ------------------------------------------------------------------- Reporting Table Person_Denormalized ---------------------------------------------------------------------------------------- - Id - Name - HomeAddress - HomeAddress_Confidence - HomeAddress_EffectiveDate - ---------------------------------------------------------------------------------------- - 123 - Joe Smith - 123 Cherry Ln - 0.713 - 2010-03-26 - ---------------------------------------------------------------------------------------- Normalized Design Person ------------------- - Id - Name - ------------------- - 123 - Joe Smith - ------------------- Person_HomeAddress ------------------------------------------------------ - PersonId - Source - Value - Effective Date - ------------------------------------------------------ - 123 - CIA - 123 Cherry Ln - 2010-03-26 - - 123 - DMV - 561 Stoney Rd - 2010-02-15 - - 123 - FBI - 676 Lancas Dr - 2010-03-01 - ------------------------------------------------------ The "Confidence" field here is generated using logic that cannot be expressed easily (if at all) using SQL so my most common operation besides inserting new values will be pulling ALL data about a person for all fields so I can generate the record for the reporting table. This is actually easier in the EAV model as I can do a single query. In the normalized design, I end up having to do 1 query per field to avoid a massive cartesian product from joining them all together.

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  • Help with 2-part question on ASP.NET MVC and Custom Security Design

    - by JustAProgrammer
    I'm using ASP.NET MVC and I am trying to separate a lot of my logic. Eventually, this application will be pretty big. It's basically a SaaS app that I need to allow for different kinds of clients to access. I have a two part question; the first deals with my general design and the second deals with how to utilize in ASP.NET MVC Primarily, there will initially be an ASP.NET MVC "client" front-end and there will be a set of web-services for third parties to interact with (perhaps mobile, etc). I realize I could have the ASP.NET MVC app interact just through the Web Service but I think that is unnecessary overhead. So, I am creating an API that will essentially be a DLL that the Web App and the Web Services will utilize. The API consists of the main set of business logic and Data Transfer Objects, etc. (So, this includes methods like CreateCustomer, EditProduct, etc for example) Also, my permissions requirements are a little complicated. I can't really use a straight Roles system as I need to have some fine-grained permissions (but all permissions are positive rights). So, I don't think I can really use the ASP.NET Roles/Membership system or if I can it seems like I'd be doing more work than rolling my own. I've used Membership before and for this one I think I'd rather roll my own. Both the Web App and Web Services will need to keep security as a concern. So, my design is kind of like this: Each method in the API will need to verify the security of the caller In the Web App, each "page" ("action" in MVC speak) will also check the user's permissions (So, don't present the user with the "Add Customer" button if the user does not have that right but also whenever the API receives AddCustomer(), check the security too) I think the Web Service really needs the checking in the DLL because it may not always be used in some kind of pre-authenticated context (like using Session/Cookies in a Web App); also having the security checks in the API means I don't really HAVE TO check it in other places if I'm on a mobile (say iPhone) and don't want to do all kinds of checking on the client However, in the Web App I think there will be some duplication of work since the Web App checks the user's security before presenting the user with options, which is ok, but I was thinking of a way to avoid this duplication by allowing the Web App to tell the API not check the security; while the Web Service would always want security to be verified Is this a good method? If not, what's better? If so, what's a good way of implementing this. I was thinking of doing this: In the API, I would have two functions for each action: // Here, "Credential" objects are just something I made up public void AddCustomer(string customerName, Credential credential , bool checkSecurity) { if(checkSecurity) { if(Has_Rights_To_Add_Customer(credential)) // made up for clarity { AddCustomer(customerName); } else // throw an exception or somehow present an error } else AddCustomer(customerName); } public void AddCustomer(string customerName) { // actual logic to add the customer into the DB or whatever // Would it be good for this method to verify that the caller is the Web App // through some method? } So, is this a good design or should I do something differently? My next question is that clearly it doesn't seem like I can really use [Authorize ...] for determining if a user has the permissions to do something. In fact, one action might depend on a variety of permissions and the View might hide or show certain options depending on the permission. What's the best way to do this? Should I have some kind of PermissionSet object that the user carries around throughout the Web App in Session or whatever and the MVC Action method would check if that user can use that Action and then the View will have some ViewData or whatever where it checks the various permissions to do Hide/Show?

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  • Magento Onepage Success Conversion Tracking Design Pattern

    - by user1734954
    My intent is to track conversions through multiple channels by inserting third party javascript (for example google analytics, optimizely, pricegrabber etc.) into the footer of onepage success . I've accomplished this by adding a block to the footer reference inside of the checkout success node within local.xml and everything works appropriately. My questions are more about efficiency and extensibility. It occurred to me that it would be better to combine all of the blocks into a single block reference and then use a various methods acting on a single call to the various related models to provide the data needed for insertion into the javascript for each of the conversion tracking scripts. Some examples of the common data that conversion tracking may rely on(pseudo): Order ID , Order Total, Order.LineItem.Name(foreach) and so on Currently for each of the scripts I've made a call to the appropriate model passing the customers last order id as the load value and the calling a get() assigning the return value to a variable and then iterating through the data to match the values with the expectations of the given third party service. All of the data should be pulled once when checkout is complete each third party services may expect different data in different formats Here is an example of one of the conversion tracking template files which loads at the footer of checkout success. $order = Mage::getModel('sales/order')->loadByIncrementId(Mage::getSingleton('checkout/session')->getLastRealOrderId()); $amount = number_format($order->getGrandTotal(),2); $customer = Mage::helper('customer')->getCustomer()->getData(); ?> <script type="text/javascript"> popup_email = '<?php echo($customer['email']);?>'; popup_order_number = '<?php echo $this->getOrderId() ?>'; </script> <!-- PriceGrabber Merchant Evaluation Code --> <script type="text/javascript" charset="UTF-8" src="https://www.pricegrabber.com/rating_merchrevpopjs.php?retid=<something>"></script> <noscript><a href="http://www.pricegrabber.com/rating_merchrev.php?retid=<something>" target=_blank> <img src="https://images.pricegrabber.com/images/mr_noprize.jpg" border="0" width="272" height="238" alt="Merchant Evaluation"></a></noscript> <!-- End PriceGrabber Code --> Having just a single piece of code like this is not that big of a deal, but we are doing similar things with a number of different third party services. Pricegrabber is one of the simpler examples. A more sophisticated tracking service expects a comma separated list of all of the product names, ids, prices, categories , order id etc. I would like to make it all more manageable so my idea to do the following: combine all of the template files into a single file Develop a helper class or library to deliver the data to the conversion template Goals Include Extensibility Minimal Model Calls Minimal Method Calls The Questions 1. Is a Mage helper the best route to take? 2. Is there any design pattern you may recommend for the "helper" class? 3. Why would this the design pattern you've chosen be best for this instance?

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  • WinForm Design View Error

    - by Ramiz Uddin
    I'm getting the following error on form design: Hide Call Stack at EnvDTE80.CodeModel2.DotNetNameFromLanguageSpecific(String LanguageName) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.CodeTypeDeclarationFromCodeClass(CodeClass vsClass) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.OnNamespacePopulateTypes(Object sender, EventArgs e) at System.CodeDom.CodeNamespace.get_Types() at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.Parse(TextReader codeStream) at Microsoft.VisualStudio.Design.Serialization.CodeDom.MergedCodeDomParser.System.CodeDom.Compiler.ICodeParser.Parse(TextReader stream) at System.CodeDom.Compiler.CodeDomProvider.Parse(TextReader codeStream) at Microsoft.VisualStudio.Shell.Design.Serialization.CodeDom.CodeDomDocDataAdapter.get_CompileUnit() at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager) at System.ComponentModel.Design.Serialization.BasicDesignerLoader.BeginLoad(IDesignerLoaderHost host) Need help!

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  • Is it a good object-oriented-design practice to send a pointer to private data to another class?

    - by Denis
    Hello everyone, There is well known recommendation not to include into class interface method that returns a pointer (or a reference) to private data of the class. But what do you think about public method of a class that sends to another class a pointer to the private data of the first one. For example: class A { public: void fA(void) {_b.fB(&_var)}; private: B _b; int _var; }; I think that it is some sort of data hiding damage: the private data define state of their own class, so why should one class delegate changes of its own state to another one? What do you think? Denis

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  • Working with PHP and MySQL - need a good and secure design with OO design

    - by Andrew
    I am new to PHP- first time developer. I am working on my web application and it is nearly done; nevertheless, most of my sql was done directly via code using direct mysql requests. This is the way I approached it: In classes_db.php I declared the db settings and created methods that I use to open and close DB connections. I declare those objects on my regular pages: class classes_db { public $dbserver = 'server; public $dbusername = 'user'; public $dbpassword = 'pass'; public $dbname = 'db'; function openDb() { $dbhandle = mysql_connect($this->dbserver, $this->dbusername, $this->dbpassword); if (!$dbhandle) { die('Could not connect: ' . mysql_error()); } $selected = mysql_select_db($this->dbname, $dbhandle) or die("Could not select the database"); return $dbhandle; } function closeDb($con) { mysql_close($con); } } On my regular page, I do this: <?php require 'classes_db.php'; session_start(); //create instance of the DB class $db = new classes_db(); //get dbhandle $dbhandle = $db->openDb(); //process query $result = mysql_query("update user set username = '" . $usernameFromForm . "' where iduser= " . $_SESSION['user']->iduser); //close the connection if (isset($dbhandle)) { $db->closeDb($dbhandle); } ?> My questions is: how to do it right and make it OO and secure? I know that I need incorporate prepared queries- how to do it the best way? Please provide some code

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  • are there any useful datasets available on the web for data mining?

    - by niko
    Hi, Does anyone know any good resource where example (real) data can be downloaded for experimenting statistics and machine learning techniques such as decision trees etc? Currently I am studying machine learning techniques and it would be very helpful to have real data for evaluating the accuracy of various tools. If anyone knows any good resource (perhaps csv, xls files or any other format) I would be very thankful for a suggestion.

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  • Server Design Enquiry [closed]

    - by Brandon Gelfand
    I am really new to this and am having trouble with how I can store information from a website. I am going to be making a site similar to dropbox for my company and there is gonna be around 40 TB of space that we need to be able to access on the go, for instance pull the file up on the phone or off our laptop using the internet. Obviously using an Amazon S3 server is not the most cost effective way of doing this so how can I make my own server to hold all of the info and communicate to it from a website? Please I need as much help as possible, like a blueprint or something. Thanks and sorry for the noobish question but I can't really find an exact answer to my question.

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  • MVC - Cocoa interface - Cocoa Design pattern book

    - by Idan
    So I started reading this book: http://www.amazon.com/Cocoa-Design-Patterns-Erik-Buck/dp/0321535022 On chapter 2 it explains about the MVC design pattern and gives and example which I need some clarification to. The simple example shows a view with the following fields: hourlyRate, WorkHours, Standarthours , salary. The example is devided into 3 parts : View - contains some text fiels and a table (the table contains a list of employees' data). Controller - comprised of NSArrayController class (contains an array of MyEmployee) Model - MyEmployee class which describes an employee. MyEmployee class has one method which return the salary according to the calculation logic, and attributes in accordance with the view UI controls. MyEmployee inherits from NSManagedObject. Few things i'm not sure of : 1. Inside the MyEmplpyee class implemenation file, the calculation method gets the class attributes using sentence like " [[self valueForKey:@"hourlyRate"] floatValue];" Howevern, inside the header there is no data member named hourlyRate or any of the view fields. I'm not quite sure how does it work, and how it gets the value from the right view field. (does it have to be the same name as the field name in the view). maybe the conncetion is made somehow using the Interface builder and was not shown in the book ? and more important: 2. how does it seperate the view from the model ? let's say ,as the book implies might happen, I decide one day to remove one of the fields in the view. as far as I understand, that means changing the way the salary method works in MyEmplpyee (cause we have one field less) , and removing one attribute from the same calss. So how is that separate the View from the Model if changing one reflect on the other ? I guess I get something wrong... Any comments ? Thanks

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  • Design Patterns Recommendation for Filtering Option

    - by Tarik
    Hi people, I am thinking to create a filter object which filters and delete everything like html tags from a context. But I want it to be independent which means the design pattern I can apply will help me to add more filters in the future without effecting the current codes. I thought Abstract Factory but it seems it ain't gonna work out the way I want. So maybe builder but it looks same. I don't know I am kinda confused, some one please recommend me a design pattern which can solve my problem but before that let me elaborate the problem a little bit. Lets say I have a class which has Description field or property what ever. And I need filters which remove the things I want from this Description property. So whenever I apply the filter I can add more filter in underlying tier. So instead of re-touching the Description field, I can easily add more filters and all the filters will run for Description field and delete whatever they are supposed to delete from the Description context. I hope I could describe my problem. I think some of you ran into the same situation before. Thanks in advance...

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  • iPhone User Interface Design

    - by Blaenk
    Hey guys, I've just had a nagging question for a while regarding iPhone app user interfaces. For example, consider WeightBot's User Interface. I am wondering, how are most of these user interfaces created? In general, of course. Is there a way to simply design controls (that is, the images) in a program like Photoshop, then use that 'skin' for controls in UIKit? I realize that there are some controls that are probably created by the programmer (custom controls), but I'm referring to the ready-made ones that come in UIKit. In other words, is the concept similar to 'splicing' web site designs? Where a designer draws out the design of the website in something like Photoshop, and then it is cut up into pieces which can be applied to form the actual website? I know this can be done for UIButtons, can this also be done for other controls, and is this how it is usually done? Or perhaps this is done with Core Animation? I've heard this from time to time, so does this mean that the User Interfaces are 'hard-coded'? Or is Core Animation only use for the 'effects', such as applying the glowing effect to the numbers in WeightBot? If there are any resources you can point me to I would really appreciate it. Thanks!

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  • “if” statement vs OO Design - 2

    - by hilal
    I encountered similar problem “if” statement vs OO Design - 1 but it is slightly different. Here is the problem that open the popup (different objects/popups) onValueChange of listbox Popup1 p1; // different objects Popup2 p2; // different objects Popup3 p3; ... listbox.add("p1"); listbox.add("p2"); listbox.add("p3"); ... listbox.addChangeHandler() { if(getSelectedItem().equals("p1")){ p1 = new Popup1(); p1.show(); } else if() {...} .... } I don't want to write "if" that if p1 then p1 = new Popup1(); p1.center(); How I can handle this situation? Any design-pattern? Here is my solution but it is so costly map() { map.put("p1", new Popup1()); map.put("p2", new Popup2()); map.put("p3", new Popup3()); } onValueChange() { map.get(selectedItem).show(); } One drawback is initialization all the popups. but it is require only when valueChange

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  • Best Practice, objects design ASP.NET MVC

    - by DoomStone
    Hello Stackoverflow I have a code design question that have been torbeling me for a while, you see I’m doing a refactoring of my website Cosplay Denmark, a site where cospalyers can upload images of them self in their costumes. The original site was done in php, Zend MVC, but my refactoring is being done in ASP.NET MVC 2. If you take the site http://www.cosplaydanmark.dk/Costumes/ (You can switch to English in the left column (Sprog)) Here you see a list of all the anime’s we have on the site with images, we show the name, how many different characters and how many images there are under this anime. http://www.cosplaydanmark.dk/Costumes/Bleach If you click on an anime will you get a list of characters within the given anime which we have images in, here do we show the character name, how many galleries and how many images. http://www.cosplaydanmark.dk/Costumes/Bleach/Ichigo_Kurosaki/ If you click on the character name, will you get a list of the galleries under the given character in the given anime. Here we have some information about the gallery, such as image count. http://www.cosplaydanmark.dk/Costumes/Bleach/Ichigo_Kurosaki/Admi/ Should you click the gallery do you get a list of the images in the gallery. My database look like this at the moment. As you can might imagine there are a lot of different query’s to create the site, on the first site I need to do a select on the on the “animes” table and for each result, I need to do a count select on characters and galleries. My plan to create this will be one of the following Where the IList, would be a lazy load list. But I can’t decide what would be the best solution for this would be, also if there is a better way of doing this. My priority is to have good performance with a minimum lose of features and code upkeep. I’m using a service pattern with a linq to sql repository. My design is not absolute, I’m willing to change it if it could increase performance :D I hope that I have describe my question good enough for you to understand what I mean, but ask away if there are anything I have missed.

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  • C# Item system design approach, should I use abstract classes, interfaces or virutals?

    - by vexe
    I'm working on a Resident Evil 1/2/3/0/Remake type of game. Currently I've done a big part of the inventory system (here's a link if you wanna see my inventory, pretty outdated, added a lot of features and made a lot of enhancements) Now I'm thinking about how to approach the items system, If you've played any Resident Evil game or any of its likes you should be familiar with what I'm trying to achieve. Here's a very simple category I made for the items: So you have different items, with different operations you could perform on them, there are usable items that you could use, like for example herbs and first aid kits that 'using' them would affect your health, keys to unlock doors, and equipable items that you could 'equip' like weapons. Also, you can 'combine' two items together to get new one, like for example mixing a green and red herb would give you a new type of herb, or combining a lighter with a paper, would give you a burnt paper, or ammo with a gun, would reload the gun or something. etc. You know the usual RE drill. Not all items are 'transformable', in that, for example: lighter + paper = burnt paper (it's the paper that 'transforms' to burnt paper and not the lighter, the lighter is not transformable it will remain as it is) green herb + red herb = newHerb1 (both herbs will vanish and transform to this new type of herb) ammo + gun = reload gun (ammo state will remain as it is, it won't change but it will just decrease, nothing will happen to the gun it just gets reloaded) Also a key note to remember is that you can't just combine items randomly, each item has a 'mating' item(s). So to sum up, different items, and different operations on them. The question is, how to approach this, design-wise? I've been learning about interfaces, but it just doesn't quite get into my head, I mean, why not just use classes with the good old inheritance? I know the technical details of interfaces and that the cool thing about them is that they don't require an inheritance chain, but I just can't see how to use them properly, that is, if they were the right thing to use here. So should I go with just classes and inheritance? just like in the tree I showed you? or should I think more about how to use interfaces? (IUsable, IEquipable, ITransformable) - why not just use classes UsableItem, Equipable item, TransformableItem? I want something that won't give me headaches in the long run, something resilient/flexible to future changes. I'm OK using classes, but I smell something better here. The way I'm thinking is to possibly use both inheritance and interfaces, so that you have a branch like this: item - equipable - weapon. but then again, the weapon has methods like 'reload' 'examine' 'equip' some of them 'combine' so I'm thinking to make weapon implement ICombinable?... not all items get used the same way, using herbs will increase your health, using a key will open a door, so IUsable maybe? Should I use a big database (XML for example) for all the items, items names, mates, nRowsReq, nColsReq, etc? Thanks so much for your answers in advanced, note that demo 3 is coming after I'm done with items :D

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  • Java - Is this a bad design pattern?

    - by Walter White
    Hi all, In our application, I have seen code written like this: User.java (User entity) public class User { protected String firstName; protected String lastName; ... getters/setters (regular POJO) } UserSearchCommand { protected List<User> users; protected int currentPage; protected int sortColumnIndex; protected SortOder sortOrder; // the current user we're editing, if at all protected User user; public String getFirstName() {return(user.getFirstName());} public String getLastName() {return(user.getLastName());} } Now, from my experience, this pattern or anti-pattern looks bad to me. For one, we're mixing several concerns together. While they're all user-related, it deviates from typical POJO design. If we're going to go this route, then shouldn't we do this instead? UserSearchCommand { protected List<User> users; protected int currentPage; protected int sortColumnIndex; protected SortOder sortOrder; // the current user we're editing, if at all protected User user; public User getUser() {return(user);} } Simply return the user object, and then we can call whatever methods on it as we wish? Since this is quite different from typical bean development, JSR 303, bean validation doesn't work for this model and we have to write validators for every bean. Does anyone else see anything wrong with this design pattern or am I just being picky as a developer? Walter

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  • Database design for invoices, invoice lines & revisions

    - by FreshCode
    I'm designing the 2nd major iteration of a relational database for a franchise's CRM (with lots of refactoring) and I need help on the best database design practices for storing job invoices and invoice lines with a strong audit trail of any changes made to each invoice. Current schema Invoices Table InvoiceId (int) // Primary key JobId (int) StatusId (tinyint) // Pending, Paid or Deleted UserId (int) // auditing user Reference (nvarchar(256)) // unique natural string key with invoice number Date (datetime) Comments (nvarchar(MAX)) InvoiceLines Table LineId (int) // Primary key InvoiceId (int) // related to Invoices above Quantity (decimal(9,4)) Title (nvarchar(512)) Comment (nvarchar(512)) UnitPrice (smallmoney) Revision schema InvoiceRevisions Table RevisionId (int) // Primary key InvoiceId (int) JobId (int) StatusId (tinyint) // Pending, Paid or Deleted UserId (int) // auditing user Reference (nvarchar(256)) // unique natural string key with invoice number Date (datetime) Total (smallmoney) Schema design considerations 1. Is it sensible to store an invoice's Paid or Pending status? All payments received for an invoice are stored in a Payments table (eg. Cash, Credit Card, Cheque, Bank Deposit). Is it meaningful to store a "Paid" status in the Invoices table if all the income related to a given job's invoices can be inferred from the Payments table? 2. How to keep track of invoice line item revisions? I can track revisions to an invoice by storing status changes along with the invoice total and the auditing user in an invoice revision table (see InvoiceRevisions above), but keeping track of an invoice line revision table feels hard to maintain. Thoughts? 3. Tax How should I incorporate sales tax (or 14% VAT in SA) when storing invoice data?

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  • Database design for credit based purchases

    - by FreshCode
    I need an elegant way to implement credit-based purchases for an online store with a small variety of products which can be purchased using virtual credit or real currency. Alternatively, products could only be priced in credits. Previous work I have implemented credit-based purchasing before using different product types (eg. Credit, Voucher or Music) with post-order processing to assign purchased credit to users in the form of real currency, which could subsequently be used to discount future orders' charge totals. This worked fairly well as a makeshift solution, but did not succeed in disconnecting the virtual currency from the real currency, which is what I'd like to do, since spending credits is psychologically easier for customers than spending real currency. Design I need guidance on designing the database correctly with support for the simultaneous bulk purchase of credits at a discount along with real currency products. Alternatively, should all products be priced in credits and only credit have a real currency value? Existing Database Design Partial Products table: ProductId Title Type UnitPrice SalePrice Partial Orders table: OrderId UserId (related to Users table, not shown) Status Value Total Partial OrderItems table (similar to CartItems table): OrderItemId OrderId (related to Orders table) ProductId (related to Products table) Quantity UnitPrice SalePrice Prospective UserCredits table: CreditId UserId (related to Users table, not shown) Value (+/- value. Summed over time to determine saldo.) Date I'm using ASP.NET MVC and LINQ-to-SQL on a SQL Server database.

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  • Database design for sharing photos site?

    - by javaLearner.java
    I am using php and mysql. If I want to do a sharing photos website, whats the best database design for upload and display photos. This is what I have in mind: domain: |_> photos |_> user Logged in user will upload photo in [http://www.domain.com/user/upload.php] The photos are stored in filesystems, and the path-to-photos stored in database. So, in my photos folder would be like: photos/userA/subfolders+photos, photos/userB/subfolders+photos, photos/userC/subfolders+photos etc Public/others people may view his photo in: [http://www.domain.com/photos/user/?photoid=123] where 123 is the photoid, from there, I will query from database to fetch the path and display the image. My questions: Whats the best database design for photo-sharing website (like flickr)? Will there be any problems if I keep creating new folder in "photos" folder. What if hundreds of thousands users registered? Whats the best practices What size of photos should I keep? Currently I only stored thumbnail (100x100) and (max) 1600x1200 px photos. What others things I should take note when developing photos-sharing website?

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  • Design: Website calling a webservice on the same machine

    - by Chris L
    More of a design/conceptual question. At work the decision was made to have our data access layer be called through webservices. So our website would call the webservices for any/all data to and from the database. Both the website & the webservices will be on the same machine(so no trip across the wire), but the database is on a separate machine(so that would require a trip across the wire regardless). This is all in-house, the website, webservice, and database are all within the same company(AFAIK, the webservices won't be reused by another other party). To the best of my knowledge: the website will open a port to the webservices, and the webservices will in turn open another port and go across the wire to the database server to get/submit the data. The trip across the wire can't be avoided, but I'm concerned about the webservices standing in the middle. I do agree there needs to be distinct layers between the functionality(such as business layer, data access layer, etc...), but this seems overly complex to me. I'm also sensing there will be some performance problems down the line. Seems to me it would be better to have the (DAL)assemblies referenced directly within the solution, thus negating the first port to port connection. Any thoughts(or links) both for and against this idea would be appreciated P.S. We're a .NET shop(migrating from vb to C# 3.5)

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  • Movies recommendation engine conceptual database design

    - by Supyxy
    I am working at an movie recommendations engine and i'm facing a DB design issue. My actual database looks like this: MOVIES [ID,TITLE] KEYWORDS_TABLE [ID,KEY_ID] - where ID is Foreign Key for MOVIES.id and KEY_ID is a key for a text keywords table This is not the entire DB, but i showed here what's important for my problem. I have about 50,000 movies and about 1,3 milion keywords correlations, and basically my algorithm consists in extracting all the who have the same keywords with a given movie, then ordering them by the number of keywords correlations. For example i looked for a movie similar to 'Cast away' and it returned 'Six days and six nights' because it had the most keywords correlations (4 keywords): Island Airplane crash Stranded Pilot The algorithm is based on more factors, but this one is the most important and the most difficult for the approach. Basically what i do now is getting all the movies that have at least one keyword similar to the given movie and then ordering them by other factors which are not important for a moment. There wouldn't be any problem if there weren't so many records, a query lasts in many cases up to 10-20 seconds and some of them return even over 5000 movies. Someone already helped me on here (thanks Mark Byers) with optimizing the query but that's not enough because it takes too longer SELECT DISTINCT M.title FROM keywords_table K1 JOIN keywords_table K2 ON K2.key_id = K1.key_id JOIN movies M ON K2.id = M.id WHERE K1.id = 4 So i thought it would be better if i pre-made those lists with movies recommendations for each movie, but i'm not sure how to design the tables.. whatever is it a good idea or how would you take this approach?

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  • Android Multiple Handlers Design Question

    - by Soumya Simanta
    This question is related to an existing question I asked. I though I'll ask a new question instead of replying back to the other question. Cannot "comment" on my previous question because of a word limit. Marc wrote - I've more than one Handlers in an Activity." Why? If you do not want a complicated handleMessage() method, then use post() (on Handler or View) to break the logic up into individual Runnables. Multiple Handlers makes me nervous. I'm new to Android. Is having multiple handlers in a single activity a bad design ? I'm new to Android. My question is - is having multiple handlers in a single activity a bad design ? Here is the sketch of my current implementation. I've a mapActivity that creates a data thread (a UDP socket that listens for data). My first handler is responsible for sending data from the data thread to the activity. On the map I've a bunch of "dynamic" markers that are refreshed frequently. Some of these markers are video markers i.e., if the user clicks a video marker, I add a ViewView that extends a android.opengl.GLSurfaceView to my map activity and display video on this new vide. I use my second handler to send information about the marker that the user tapped on ItemizedOverlay onTap(int index) method. The user can close the video view by tapping on the video view. I use my third handler for this. I would appreciate if people can tell me what's wrong with this approach and suggest better ways to implement this. Thanks.

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  • Which Table Should be Master and Child in Database Design

    - by Jason
    I am quickly learning the ins and outs of database design (something that, as of a week ago, was new to me), but I am running across some questions that don't seem immediately obvious, so I was hoping to get some clarification. The question I have right is about foreign keys. As part of my design, I have a Company table. Originally, I had included address information directly within the table, but, as I was hoping to achieve 3NF, I broke out the address information into its own table, Address. In order to maintain data integrity, I created a row in Company called "addressId" as an INT and the Address table has a corresponding addressId as its primary key. What I'm a little bit confused about (or what I want to make sure I'm doing correctly) is determining which table should be the master (referenced) table and which should be the child (referencing) table. When I originally set this up, I made the Address table the master and the Company the child. However, I now believe this is wrong due to the fact that there should be only one address per Company and, if a Company row is deleted, I would want the corresponding Address to be removed as well (CASCADE deletion). I may be approaching this completely wrong, so I would appreciate any good rules of thumb on how to best think about the relationship between tables when using foreign keys. Thanks!

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