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  • Why use link classes in oql instead of classes that contain links

    - by Isaac
    itop abstracts its very complex database design with an object query language (oql). For this there are classes definded, like 'Ticket' and 'Server'. Now a Ticket usually is linked to a Server. In my naive way I would give the Ticket class an attribute 'affected_server_list', where I could reference the affected servers. itop does it different: neither Servers nor Tickets know of each other. Instead there is a class 'linkTicketToServer', which provides the link between the two. The first thing I noticed is that it makes oql queries more complex. So I wondered why they designed it this way. One thing that occured to me is that it allows for more flexiblity, in that I can add links without modifying the original classes. Is this allready why one would implement it this way, or are there other reasons for this kind of design?

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  • How can I get pictures from Shotwell on the notebook to the desktop?

    - by Meng Tian
    My father has a desktop and a notebook. The desktop is way more powerful and has RAID set up, so he uses it for editing and storing his pictures. But he spends several months a year away from home. So he has a notebook for this. He imports the pictures into shotwell on his computer. He likes to organise his pictures on the notebook already, by creating and naming the right events, deleting pictures and sometimes editing a bit. When he is back home, he wants to get his pictures on the desktop, without losing the names of the events in shotwell. Sadly, one cannot merge two shotwell databases, nor is it possible to import another database. Do you know any way, I can manage this? Or did I just miss something?

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  • Save BIG on Storage &mdash; with Oracle Advanced Compression

    - by [email protected]
    Recently, we published a podcast revealing just how much Oracle benefits from its internal use of Oracle Database 11g and Advanced Compression. With hundreds of TB and millions of dollars saved, Oracle Advanced Compression is dramatically reducing storage costs and substantially improving efficiency across the company. Now, here's your chance: Meet the experts, have your questions answered by them and immediately start using your storage more efficiently: On April 14th, join me for a live Webcast with Oracle's Tim Shetler, Vice President of Product Management and Bill Hodak, Principal Product Manager, to learn just how Oracle Advanced Compression can Reduce disk space requirements for all types of data Improve query and storage performance Lower storage costs throughout the datacenter Register here! var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www."); document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E")); try { var pageTracker = _gat._getTracker("UA-13185312-1"); pageTracker._trackPageview(); } catch(err) {}

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  • Creating symlink for Postgres

    - by Edwin
    As a developer, I often ssh right into my local database, just to test my application before pushing my code. However, I find that every time I want to access Postgres, I have to type in postgres@ubuntu:~$ /usr/local/pgsql/bin/psql test whereas on my work machine, all I have to do is type postgres@ubuntu:~$ psql --dbname=test --username=user I tried creating a symlink, which was successful, but whenever I try connecting to it through this shortcut, I get the following error message: psql: could not connect to server: No such file or directory Is the server running locally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"? How do I get this to work? In case it makes any difference, I'm using a self-compiled version of the 9.1.x series.

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  • Is there really Object-relational impedance mismatch?

    - by user52763
    It is always stated that it is hard to store applications objects in relational databases - the object-relational impedance mismatch - and that is why Document databases are better. However, is there really an impedance mismatch? And object has a key (albeit it may be hidden away by the runtime as a pointer to memory), a set of values, and foreign keys to other objects. Objects are as much made up of tables as it is a document. Neither really fit. I can see a use for databases to model the data into specific shapes for scenarios in the application - e.g. to speed up database lookup and avoid joins, etc., but won't it be better to keep the data as normalized as possible at the core, and transform as required?

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  • Developing a live video-streaming website

    - by cawecoy
    I'm a computer science student and know a little about some technology to start developing my website, like PHP, RubyOnRails and Python, and MySQL and PostgreSQL for Database. I need to know what are the best (secure, stable, low-price, etc) to get started, based on my business information: My website will be a live video-streaming one, similar to livestream.com We need to provide a secure service for our customers. They need to have a page to create and configure their own Live-Streaming-Videos, get statistics, etc. We work with Wowza Media Server ruuning on an Apache Server In addition, I would like to know some good practices for this kind of website development, as I am new to this. Thanks in advance!

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  • Is Java's ElementCollection Considered a Bad Practice?

    - by SoulBeaver
    From my understanding, an ElementCollection has no primary key, is embedded with the class, and cannot be queried. This sounds pretty hefty, but it allows me the comfort of writing an enum class which also helps with internationalization (using the enum key for lookup in my ResourceBundle). Example: We have a user on a media site and he can choose in which format he downloads the files @Entity @Table(name = "user") public class User { /* snip other fields */ @Enumerated @ElementCollection( targetClass = DownloadFilePreference.class, fetch = FetchType.EAGER ) @CollectionTable(name = "download_file_preference", joinColumns = @JoinColumn(name = "user_id") ) @Column(name = "name") private Set<DownloadFilePreference> downloadFilePreferences = new HashSet<>(); } public enum DownloadFilePreference { MP3, WAV, AIF, OGG; } This seems pretty great to me, and I suppose it comes down to "it depends on your use case", but I also know that I'm quite frankly only an initiate when it comes to Database design. Some best practices suggest to never have a class without a primary key- even in this case? It also doesn't seem very extensible- should I use this and gamble on the chance I will never need to query on the FilePreferences?

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  • Oracle Developer Day: Die Oracle Datenbank in der Praxis

    - by A&C Redaktion
    Im neuen Jahr finden wieder Oracle Developer Days in verschiedenen Städten statt! In dieser speziell von den Database-Kollegen zusammengestellten Veranstaltung erfahren Sie viele Tipps und Tricks aus der Praxis und werden zu folgenden Themen auf den neuesten Stand gebracht: Die Unterschiede der Editionen und ihre Geheimnisse Umfangreiche Basisausstattung auch ohne Option Performance und Skalierbarkeit in den einzelnen Editionen Kosten- und Ressourceneinsparung leicht gemacht Sicherheit in der Datenbank Steigerung der Verfügbarkeit mit einfachen Mitteln Der Umgang mit großen Datenmengen Cloud Technologien in der Oracle Datenbank Ein Ausblick auf die Funktionen der für 2013 geplanten neuen Datenbank-Version rundet den Workshop ab. Termine, Agenda,Veranstaltungsorte und Anmeldung finden Sie hier. Melden Sie sich noch heute zur Veranstaltung an - die Teilnahme ist kostenlos!

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  • Regardig Vb.net [closed]

    - by user68999
    hi everyone i am making a project for school management and manage all the record of student so I'm using VB.net 2008 and sql server 2008. i have a problem when i enter student date of birth in text box with date&time picker in database. but i want in the search option enter the date from date&time picker and get age of all the student data in data-view grid. like student are 10 year old, 11 year old etc. so how it can possible please help..........?

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  • Learn a NoSQL or become a badass with traditional RDMS - Where is/will the work be?

    - by beck
    I'm half way through my MSc and am thinking about my dissertation which I get 3 months to work on full time. Im very comfortable with the traditional Relational Database, the question is should I work on a project where I get a good understanding of something like Cassandra, or should I really push my RDMS knowledge to the limit. Getting great at something like MySQL is a solid safe option, will there really be much work for me with Cassandra in my tool belt? I would love to do either.... Thanks for your opinions and advice.

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  • mssql or mysql: learning

    - by Yehuda
    I have been using MySQL for about 9 months now for websites, and i have become quite good in getting what I want out of the Database. However i am still missing most of the complicated parts. I have an excellent tutorial but it is on sql-server 2008. 1) Is it worth me switching over to mssql (I understand the SQL is different) so that I will learn all about SQL and databases in general? 2) Do most people use MySQL or MSSQL 3) What is best practice, and I am talking mainly for websites.

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  • query to select topic with highest number of comment +support+oppose+views

    - by chetan
    table schema title description desid replyto support oppose views browser used a1 none 1 1 12 - bad topic b2 1 2 3 14 sql database a3 none 4 5 34 - crome b4 1 3 4 12 Topic desid starts with a and comment desid starts with b .For comment replyto is the desid of topic . Its easy to select * with highest number of support+oppose+views by query "select * from [DB_user1212].[dbo].[discussions] where desid like 'a%' order by (sup+opp+visited) desc" For highest (comment +support+oppose+views ) i tried "select * from [DB_user1212].[dbo].[discussions] where desid like 'a%' order by ((select count(*) from [DB_user1212].[dbo].[discussions] where replyto = desid )+sup+opp+visited) desc" but it didn't work . Because its not possible to send desid from outer query to innner subquery .

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  • Breaking up a large PHP object used to abstract the database. Best practices?

    - by John Kershaw
    Two years ago it was thought a single object with functions such as $database->get_user_from_id($ID) would be a good idea. The functions return objects (not arrays), and the front-end code never worries about the database. This was great, until we started growing the database. There's now 30+ tables, and around 150 functions in the database object. It's getting impractical and unmanageable and I'm going to be breaking it up. What is a good solution to this problem? The project is large, so there's a limit to the extent I can change things. My current plan is to extend the current object for each table, then have the database object contain these. So, the above example would turn into (assume "user" is a table) $database->user->get_user_from_id($ID). Instead of one large file, we would have a file for every table.

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  • System that splits passwords across two servers

    - by Burning the Codeigniter
    I stumbled upon this news article on BBC, RSA splits passwords in two to foil hackers' attacks tl;dr - a (randomized) password is split in half and is stored across two separate servers, to foil hackers that gained access to either server upon a security breach. Now the main question is, how would this kind of system would be made... codespeaking, for PHP which I commonly develop on my web applications, the database password is normally stored in a configuration file, i.e. config.php with the username and password, in that case it is understandable that the passwords can be stolen if the security was compromised. However when splitting and sending the other half to the other server, how would this go on when making a communication to the other server (keeping in mind with PHP) since the other server password would be stored in a configuration file, wouldn't it? In terms of security is to keep the other server password away from the main one, just exactly how would the main server communicate, without exposing any other password, apart from the first server. This certainly makes me think...

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  • Whats a good structure to save and retrieve locations of images?

    - by Goot
    I got a java-ee application, where I collect informations about movies. Im my backend I provide data like the name, description, genre and a random uuid. I also got lots of related files, which are stored on a file server. Including some screenshots, the dvd or bluRay cover and video trailers. My current approach is: When saving the files to the fileserver, I retrieve the movies random uuid (which is the primary key btw.). I then rename the files screenshot_[UUID]_1, screenshot_[UUID]_2 ... etc. Now, there are lots of other ways to handle this, like saving all filenames in a database or creating a dir structure on the fileserver for every uuid and, e.g., return all images in the "[uuid]/screenshots" folder via REST. I expect about 30k requests a day, so the service has to be pretty performant. Whats the best way to solve this?

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  • How and what setting do you use in order to create your customized application with database? [closed]

    - by FullmetalBoy
    I have a homemade project combining with application and database. Today I'm using architecture N-tier. Totally I have 4 project in my solution in VS2010. The fourth project is a transaction layer that connect all the 3 project (one for presentation, business logic and database layer) in order to retrieve data from the database and all the way to present the data in presentation layer. Transaction layer contains entity framework 4 + customized class to carry data to the presentation layer. I always use LINQ to retrieve data in database layer. From my experience, everytime I use LINQ in relation with entity framework it always take a lot of time to retrieve data because what I believe is that my entity framework always has to reload everytime when I want to retrieve any data from the database. My question for you guys is: When you create your application connecting to a database, what architecture do you use? How do you retrieve the data from you application? Is it entity framework etc?

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  • MySQL vs. SQL Server GoDaddy, What is the difference between hosted DB and App_Data Db

    - by Nate Gates
    I'm using GoDdady for site hosting, and I'm currently using MySQL, because there are less limits on size,etc. My question is what is the difference between using a hosted GoDaddy Db such as MySQL vs. creating a SQL Server database in the the App_Data folder? My guess is security? Would it be a bad idea to use a SQL ServerDB that's located in the App_Data folder? Additional Well I am able to create a .mdf (SQL Server DB file) in the App_Data folder, but I'm really unsure if should use that or not, If I did use it it would simplify using some of the Microsoft tools. Like I said my guess is that it would be less secure, but I don't really know. I know I have a 10gb, file system limit, so I'm assuming my db would have to share that space.

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  • Immutable design with an ORM: How are sessions managed?

    - by Programmin Tool
    If I were to make a site with a mutable language like C# and use NHibernate, I would normally approach sessions with the idea of making them as create only when needed and dispose at request end. This has helped with keeping a session for multiple transactions by a user but keep it from staying open too long where the state might be corrupted. In an immutable system, like F#, I would think I shouldn't do this because it supposes that a single session could be updated constantly by any number of inserts/updates/deletes/ect... I'm not against the "using" solution since I would think that connecting pooling will help cut down on the cost of connecting every time, but I don't know if all database systems do connection pooling. It just seems like there should be a better way that doesn't compromise the immutability goal. Should I just do a simple "using" block per transaction or is there a better pattern for this?

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  • How Would You Design This Table?

    - by sooprise
    I have to create a table where each row needs to store 50 number values. Each row will always need to store 50 number values. If this was a smaller number of values, I would just make fields for each of the values, but because there are 50, this approach seems a bit cumbersome (but since it will always be 50 values, maybe this is the correct approach?). Is there a way to store an array of values in a field? This seems like a nice solution, but the concept is almost identical to creating a relational database.

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  • Point me to info about constructing filters (of lists)

    - by jah
    I would like some pointers to information which would help me understand how to go about providing the ability to filter a list of entities by their attributes as well as by attributes of related entities. As an example, imagine a web app which provides order management of some kind. Orders and related entities are stored in a relational database. And imagine that the app has an interface which lists the orders. The problem is: how does one allow the list to be filtered by, for example:- order number (an attribute) line item name (an attribute of a n-n related entity) some text in an administrative note related to the order (text found in an attribute of a 1-1 related entity) I'm trying to discover whether there is something like a standard, efficient way to construct the queries and the filtering form; or some possible strategies; or any theory on the topic; or some example code. My google foo fails me.

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  • What are the benefits of NoSQL?

    - by geekbrit
    I'm struggling to see how NoSQL brings any advantages to a system, so I'm interested in hearing from people who have chosen to use it, both the reasons they chose NoSQL, and positive and negative experiences in implementation and use. My first impressions are that NoSQL is a product of the availability of very large, very cheap storage; it seems that a million record database could easily have a 100MByte overhead in field labels embedded in the records. This goes against one of my software design instincts - remove redundancy in code and data whenever practical. However, NoSQL is being used with success in large high-traffic systems, so I must be missing something, looking forward to your responses.

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  • How to get experience in large scale databases?

    - by Justin
    I have written applications that are very small scale and the code I write works fine for them. But I have often wondered how the server side code I write would scale up from 100s of queries per day to millions. Also when looking at possible jobs/projects, people are often looking for developers with experience in this sort of high traffic database design so I would at least like to be able to say, I havent gotten to work on a project that was this popular, but I at least have tried to simulate it. Are there tools or frameworks that can generate a lot of traffic or at least simulate what would happen with traffic on different orders of magnitude so I could get some practice writing optimized code for higher traffic applicaitons?

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  • How Data Transfers differ on Smart Phones: Iphone vs. Android vs. Windows Phone

    - by MCH
    I am interested in how each individual smart phone is allowed to handle data transfers within a third-party app. I am interested in designing apps that allow customers to update, transfer, download, etc. data from their smart phone to their personal computer and vice-versa. (Ranging from just text, to XML, to a Relational Database) I only have experience with the Ipod Touch before and one particular app that maintained all the data on an online server, so to update the data on your pc or iphone you had to go online, are there other ways to do it? Like bluetooth, wireless LAN, USB, etc? I believe Apple has certain policies on this in order to control the App Store and individual Iphones. I suppose each company has a particular policy on how an app is allowed to transfer data to another system, does anyone have a good understanding of this? Thank you.

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  • c# display DB table structure

    - by user3529643
    I have a question. My code is the following : public partial class Form1 : Form { public OleDbConnection datCon; public string MyDataFile; public ArrayList tblArray; public ArrayList fldArray; public Form1() { InitializeComponent(); lvData.Clear(); lvData.View = View.Details; lvData.LabelEdit = false; lvData.FullRowSelect = true; lvData.GridLines = true; } private void DataConnection() { MyDataFile = Application.StartupPath + @"\studenti.mdb"; string MyCon = @"provider=microsoft.jet.oledb.4.0;data source=" + MyDataFile; try { datCon = new OleDbConnection(MyCon); } catch (Exception ex) { MessageBox.Show(ex.Message); } FillTreeView(); } private void GetTables(OleDbConnection cnn) { try { cnn.Open(); DataTable schTable = cnn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new Object[] { null, null, null, "TABLE" }); tblArray = new ArrayList(); foreach (DataRow datrow in schTable.Rows) { tblArray.Add(datrow["TABLE_NAME"].ToString()); } cnn.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void GetFields(OleDbConnection cnn, string tabNode) { string tabName; try { tabName = tabNode; cnn.Open(); DataTable schTable = cnn.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, new Object[] { null, null, tabName }); fldArray = new ArrayList(); foreach (DataRow datRow in schTable.Rows) { fldArray.Add(datRow["COLUMN_NAME"].ToString()); } cnn.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void FillTreeView() { tvData.Nodes.Clear(); tvData.Nodes.Add("Database"); tvData.Nodes[0].Tag = "RootDB"; GetTables(datCon); // add table node for (int i = 0; i < tblArray.Count; i++) { tvData.Nodes[0].Nodes.Add(tblArray[i].ToString()); tvData.Nodes[0].Nodes[i].Tag = "Tables"; } // add field node for (int i = 0; i < tblArray.Count; i++) { GetFields(datCon, tblArray[i].ToString()); for (int j = 0; j < fldArray.Count; j++) { tvData.Nodes[0].Nodes[i].Nodes.Add(fldArray[j].ToString()); tvData.Nodes[0].Nodes[i].Nodes[j].Tag = "Fields"; } } this.tvData.ContextMenuStrip = contextMenuStrip1; contextMenuStrip1.ItemClicked +=contextMenuStrip1_ItemClicked; } public void FillListView(OleDbConnection cnn, string tabName) { OleDbCommand cmdRead; OleDbDataReader datReader; string strField; lblTableName.Text = tabName; strField = "SELECT * FROM [" + tabName + "]"; // Initi cmdRead obiect cmdRead = new OleDbCommand(strField, cnn); cnn.Open(); datReader = cmdRead.ExecuteReader(); // fill ListView while (datReader.Read()) { ListViewItem objListItem = new ListViewItem(datReader.GetValue(0).ToString()); for (int c = 1; c < datReader.FieldCount; c++) { objListItem.SubItems.Add(datReader.GetValue(c).ToString()); } lvData.Items.Add(objListItem); } datReader.Close(); cnn.Close(); } private void ViewToolStripMenuItem_Click(object sender, EventArgs e) { DataConnection(); } public void tvData_AfterExpand(object sender, System.Windows.Forms.TreeViewEventArgs e) { string tabName; int fldCount; if (e.Node.Tag.ToString() == "Tables") { fldCount = e.Node.GetNodeCount(false); //column headers. int n = lvData.Width; double wid = n / fldCount; // width columnn for (int c = 0; c < fldCount; c++) { lvData.Columns.Add(e.Node.Nodes[c].Text, (int)wid, HorizontalAlignment.Left); } // gett table name tabName = e.Node.Text; FillListView(datCon, tabName); } } public void button1_Click(object sender, EventArgs e) { //TO DO?? } } I have a treeview populated with tables (nodes) from my database, and a listview which is populated with the data from my tables when I click on a table. As you can see I have a button1 on my form. When I click it I want it to display to me the structure of the table I selected in my treeview (a treeview node). Not too many details, just the name of the columns in my table, type of columns, primary keys. I've tried to follow many tutorials but I can t seem to manage it.

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  • Architecting persistence (and other internal systems). Interfaces, composition, pure inheritance or centralization?

    - by Vandell
    Suppose that you need to implement persistence, I think that you're generally limited to four options (correct me if I'm wrong, please) Each persistant class: Should implement an interface (IPersistent) Contains a 'persist-me' object that is a specialized object (or class) that's made only to be used the class that contains it. Inherit from Persistent (a base class) Or you can create a gigantic class (or package) called Database and make your persistence logic there. What are the advantages and problems that can come from each of one? In a small (5kloc) and algorithmically (or organisationally) simple app what is probably the best option?

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