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

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

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  • archiving strategies and limitations of data in a table

    - by Samuel
    Environment: Jboss, Mysql, JPA, Hibernate Our web application will be catering to a large amount of users (~ 1,000,000) and there are a lots of child table where user specific data are stored (e.g. personal, health, forum contributions ...). What would be the best practice to archive user & user specific information. [a] Would it be wise to move the archived user & user specific information to their respective tables within the same database (e.g. user_archive, user_forum_comments_archive ...) OR [b] Would you just mark the database entries with a flag in the original table(s) and just query only non archived entries. We have a unique constraint on User.loginid, how do you handle this requirement if the users are archived via 1-[a] (i.e if a user with loginid 'samuel' gets moved into the archive table and if a new user gets added with the same name in the original table, how would you prevent this. What would be the best strategy to address the unique key constraints. We have a requirement to selectively archive records and bring it back if necessary, will you rely on database tools are would you handle this via your persistence APIs exposed by the JPA entity model.

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  • Learning Modelling

    - by me1234
    Is there a good book which I can follow to learn modelling/doing architecture? Good samples? What would you do if you have to learn modelling from very basics? Thanks

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  • Separating weakly linked database schemas

    - by jldugger
    I've been tasked with revisiting a database schema we designed and use internally for various ticketing and reporting systems. Currently there exists about 40 tables in one Oracle database schema supporting perhaps six webapps. However, there's one unifying relationship amongst them all: a rooms table describing the room. Room name, purpose and other data are thrown into a shared table for each app. My initial idea was to pull each of these applications into a separate database, and perform joins between a given database and the room database. But I've discovered this solution prevents foreign key constraints in SQL Server 2005. It seems silly to duplicate one table for each app and keep those multiple copies synchronized. Should I just leave everything in one large DB, or is there something else I can do separate the tables without losing FK constraints?

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  • How to pass data to another droid device when the other device isn't expecting it

    - by James Black
    I am working on an application and one feature that would make it really useful is the ability to share some information, but the other device may not be expecting the data to be sent. For example, if I am reading a really good book, and I realize that a friend may like it, I could use an application to send the data to him, so he could order the book from Amazon. But, since he isn't expecting the data, I would hate for the application to be polling a server every so often, as that will be needlessly draining the battery. Ideally it would be great if there was a way to make a phone call to the target device, send a data packet and end the call. If it could be done and prevent the phone from ringing, then it would be very useful to me. I am curious if there is some way to send data between devices without polling.

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  • SO what RDF database do i use for product attribute situation initially i thought about using EAV?

    - by keisimone
    Hi, i have a similar issue as espoused in http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters i am convinced to use RDF now. only because of one of the comments made by Bill Karwin in the answer to the above issue but i already have a database in mysql and the code is in php. 1) So what RDF database should I use? 2) do i combine the approach? meaning i have a class table inheritance in the mysql database and just the weird product attributes in the RDF? I dont think i should move everything to a RDF database since it is only just products and the wide array of possible attributes and value that is giving me the problem. 3) what php resources, articles should i look at that will help me better in the creation of this? 4) more articles or resources that helps me to better understand RDF in the context of the above challenge of building something that will better hold all sorts of products' attributes and values will be greatly appreciated. i tend to work better when i have a conceptual understanding of what is going on. Do bear in mind i am a complete novice to this and my knowledge of programming and database is average at best.

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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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  • How to secure authorization of methods

    - by Kurresmack
    I am building a web site in C# using MVC.Net How can I secure that no unauthorized persons can access my methods? What I mean is that I want to make sure that only admins can create articles on my page. If I put this logic in the method actually adding this to the database, wouldn't I have business logic in my data layer? Is it a good practise to have a seperate security layer that is always in between of the data layer and the business layer to make? The problem is that if I protect at a higher level I will have to have checks on many places and it is more likely that I miss one place and users can bypass security. Thanks!

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  • What are some best practises and "rules of thumb" for creating database indexes?

    - by Ash
    I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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  • How to find good looking font color if background color is known?

    - by Mecki
    There seem to be so many color wheel, color picker, and color matcher web apps out there, where you give one color and the they'll find a couple of other colors that will create a harmonic layout when being used in combination. However most of them focus on background colors only and any text printed on each background color (if text is printed at all in the preview) is either black or white. My problem is different. I know the background color I want to use for a text area. What I need help with is choosing a couple of colors (the more, the merrier) I can use as font colors on this background. Most important is that the color will make sure the font is readable (contrast not being too low, also maybe not being too high to avoid that eyes are stressed) and of course that the combination of foreground and background just looks good. Anyone being aware of such an application? I'd prefer a web application to anything I have to download. Thanks.

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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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  • Make is more OOPey - good structure?

    - by Tom
    Hi, I just want advice on whether I could improve structure around a particular class which handles all disk access functions The structure of my program is that I have a class called Disk which gets data from flatfiles and databases on a, you guessed it, hard disk drive. I have functions like LoadTextFileToStringList, WriteStringToTextFile, DeleteLineInTextFile etc which are kind of "generic methods" In the same class I also have some more specific methods such as GetXFromDisk where X might be a particular field in a database table/query. Should I separate out the generic methods from the specialised. Should I make another class which inherits the generic methods. At the moment my class is static as there is no need to have an internal state of the class. I'm not really OOPing am I? Thanks Thomas

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  • Fowler Analysis Patterns lately?

    - by Berryl
    As much as I've always loved this one is how much I always wished there were more meaty examples of how to apply some of the concepts available. Is anyone aware of anything out there worth looking at that attempts to that? Cheers, Berryl

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  • css sprite button is jumping around

    - by Richard
    Hello everyone, Does anyone know what is causing the sprite rollover to jump around It is I think more likely a photoshop question, but I am not completely sure. I hope to get an answer here anyway, since I think most webdesigners/programmers problably worked with photoshop also. This is what I want the rollover to do example 1 and this is my testpage (see the play button) I made the sprite with spriteme.com thanks, Richard

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  • Patterns to implement this grammar into C# code

    - by MexicanHacker
    Hey guys, I'm creating this little BNF grammar and I wanted to <template>::= <types><editors> <types>::= <type>+ <type>::= <property>+ <property>::= <name><type> <editors>::= <editor>+ <editor>::= <name><type>(<textfield>|<form>|<list>|<pulldown>)+ <textfield>::= <label><property>[<editable>] <form>::= <label><property><editor> <list>::= <label><property><item-editor> <pulldown>::= <label><property><option>+ <option>::= <value> One possible solution we have in mind is to create POCO's that have annotations of the XMLSerialization namespace, like this, for example: [XMLRoot("template")] public class Template{ [XMLElement("types")] public Types types{ } } However I want to explore more solutions, what do you guys think?

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  • Getting started with nbehave

    - by dotnetdev
    Hi, I am looking at using BDD, however, when evaluating the stories/conditions I write (using nBehave), how do I check if the story passes? Do I write another library with test methods? For example, if I want to test a site for having a link called "About", do I write a method which can check this and then another method in another class library which can call the method to check the link via lambda syntax and add the relevant test and bdd attributes? Thanks

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  • How to move an element in a sorted list and keep the CouchDb write "atomic"

    - by karlthorwald
    I have elements of a list in couchdb documents. Let's say these are 3 elements in 3 documents: { "id" : "783587346", "type" : "aList", "content" : "joey", "sort" : 100.0 } { "id" : "358734ff6", "type" : "aList", "content" : "jill", "sort" : 110.0 } { "id" : "abf587346", "type" : "aList", "content" : "jack", "sort" : 120.0 } A view retrieves all "aList" documents and displays them sorted by "sort". Now I want to move the elements, when I want to move "jack" to the middle, I could do this atomic in one write and change it's sort key to 105.0. The view now returns the documents in the new sort order. After a lot of sorting I could end up with sort keys like 50.99999 and 50.99998 after some years and in extreme situations run out of digits? What can you recommend, is there a better way to do this? I'd rather keep the elements in seperate documents. Different users might edit different elements in parallel (which also can get tricky). Maybe there is a much better way?

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  • Unexpected space between DIV elements, no - not padding and not margins

    - by jon
    my code for the php page displaying the divs <?php session_start(); require_once("classlib/mainspace.php"); if (isset($_SESSION['username'])==FALSE) { header("location:login.php"); } $user = new User($_SESSION['username']); ?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <link rel="stylesheet" type="text/css" href="style/style.css" /> <title>SimpleTask - Home</title> </head> <body> <div id="main"> <div id="menu"> <div id="items"> <ul> <li><a href="home.php">home</a></li> <li>&bull;</li> <li><a href="projects.php">my projects</a></li> <li>&bull;</li> <li><a href="comments.php">my comments</a></li> </ul> </div> <div id="user"> <p>Welcome, <?php echo $user->GetRealName(); ?><br/><a href="editprofile.php">edit profile</a> &bull; <a href="logout.php">logout</a></p> </div> </div> <div id="content"> <h1>HOME</h1> </div> <div id="footer"> <p>footer text goes here here here here</p> </div> </div> </body> </html> and you can find my CSS here http://tasker.efficaxdevelopment.com/style/style.css and to view the live page go here http://tasker.efficaxdevelopment.com/login.php username:admin password:password

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