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  • What are the Options for Storing Hierarchical Data in a Relational Database?

    - by orangepips
    Good Overviews One more Nested Intervals vs. Adjacency List comparison: the best comparison of Adjacency List, Materialized Path, Nested Set and Nested Interval I've found. Models for hierarchical data: slides with good explanations of tradeoffs and example usage Representing hierarchies in MySQL: very good overview of Nested Set in particular Hierarchical data in RDBMSs: most comprehensive and well organized set of links I've seen, but not much in the way on explanation Options Ones I am aware of and general features: Adjacency List: Columns: ID, ParentID Easy to implement. Cheap node moves, inserts, and deletes. Expensive to find level (can store as a computed column), ancestry & descendants (Bridge Hierarchy combined with level column can solve), path (Lineage Column can solve). Use Common Table Expressions in those databases that support them to traverse. Nested Set (a.k.a Modified Preorder Tree Traversal) First described by Joe Celko - covered in depth in his book Trees and Hierarchies in SQL for Smarties Columns: Left, Right Cheap level, ancestry, descendants Compared to Adjacency List, moves, inserts, deletes more expensive. Requires a specific sort order (e.g. created). So sorting all descendants in a different order requires additional work. Nested Intervals Combination of Nested Sets and Materialized Path where left/right columns are floating point decimals instead of integers and encode the path information. Bridge Table (a.k.a. Closure Table: some good ideas about how to use triggers for maintaining this approach) Columns: ancestor, descendant Stands apart from table it describes. Can include some nodes in more than one hierarchy. Cheap ancestry and descendants (albeit not in what order) For complete knowledge of a hierarchy needs to be combined with another option. Flat Table A modification of the Adjacency List that adds a Level and Rank (e.g. ordering) column to each record. Expensive move and delete Cheap ancestry and descendants Good Use: threaded discussion - forums / blog comments Lineage Column (a.k.a. Materialized Path, Path Enumeration) Column: lineage (e.g. /parent/child/grandchild/etc...) Limit to how deep the hierarchy can be. Descendants cheap (e.g. LEFT(lineage, #) = '/enumerated/path') Ancestry tricky (database specific queries) Database Specific Notes MySQL Use session variables for Adjacency List Oracle Use CONNECT BY to traverse Adjacency Lists PostgreSQL ltree datatype for Materialized Path SQL Server General summary 2008 offers HierarchyId data type appears to help with Lineage Column approach and expand the depth that can be represented.

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  • Free or open source dictionaries

    - by jack
    I'm working on a multi-lingual search engine. I need to map keywords in English to corresponding words in following languages: Bulgarian Catalan Chinese Crotian Czech Danish Dutch Finish French German Greek Hungarian Italian Japanese Korean Lithuanian Litvian Norwegian Polish Portuguese Romanian Russian Slovak Slovenian Spanish Swedish Thai Ukrainian Vietnamese I already known eudict and stardict. Could you recommend some other free or open source dictionaries cover one or more above languages?

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  • How to "merge" page "\Default.aspx" and "\"?

    - by IrenaB
    our site is developed in ASP.NET. We want to block Default.aspx page from Google and other search engines. How can we "close" the Default.aspx page so that it is not accessible? Or is there another way to solve the problem so that we don't create duplicate content.

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  • Javascript link SEO

    - by vetri
    I have a page where in a photo and description link is there, i want replace the hard coded link with a javascript,which will add them,as i dont want the search engine to scroll the links.I dont wanna use "nofollow" attribute.How to code it in js.

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  • How to display specific data from a file

    - by user1067332
    My program is supposed to ask the user for firstname, lastname, and phone number till the users stops. Then when to display it asks for the first name and does a search in the text file to find all info with the same first name and display lastname and phones of the matches. import java.util.*; import java.io.*; import java.util.Scanner; public class WritePhoneList { public static void main(String[] args)throws IOException { BufferedWriter output = new BufferedWriter(new FileWriter(new File( "PhoneFile.txt"), true)); String name, lname, age; int pos,choice; try { do { Scanner input = new Scanner(System.in); System.out.print("Enter First name, last name, and phone number "); name = input.nextLine(); output.write(name); output.newLine(); System.out.print("Would you like to add another? yes(1)/no(2)"); choice = input.nextInt(); }while(choice == 1); output.close(); } catch(Exception e) { System.out.println("Message: " + e); } } } Here is the display code, when i search for a name, it finds a match but displays the last name and phone number of the same name 3 times, I want it to display all of the possible matches with the first name. import java.util.*; import java.io.*; import java.util.Scanner; public class DisplaySelectedNumbers { public static void main(String[] args)throws IOException { String name; String strLine; try { FileInputStream fstream = new FileInputStream("PhoneFile.txt"); // Get the object of DataInputStream DataInputStream in = new DataInputStream(fstream); BufferedReader br = new BufferedReader(new InputStreamReader(in)); Scanner input = new Scanner(System.in); System.out.print("Enter a first name"); name = input.nextLine(); strLine= br.readLine(); String[] line = strLine.split(" "); String part1 = line[0]; String part2 = line[1]; String part3 = line[2]; //Read File Line By Line while ((strLine= br.readLine()) != null) { if(name.equals(part1)) { // Print the content on the console System.out.print("\n" + part2 + " " + part3); } } }catch (Exception e) {//Catch exception if any System.out.println("Error: " + e.getMessage()); } } }

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  • preg_match , regexp , php , extract text from html

    - by Michael
    I'm trying to extract "Florida (FL)" from http://www.auctionarms.com/search/displayitem.cfm?itemnum=9736364&oh=216543. My code is //get location $pattern = "/(State)<\/i\:<\/td(.*)<\/td/"; preg_match_all($pattern, $htmlContent, $matches); print_r($matches); any idea why is not working ?

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  • What is the difference between PS1 and PROMPT_COMMAND

    - by Jed Daniels
    While taking a look at this awesome thread I noticed that some examples use PS1="Blah Blah Blah" and some use PROMPT_COMMAND="Blah Blah Blah" (and some use both) when setting the prompt in a bash shell. What is the difference between the two? An SO search and even a bit of broader google searching aren't getting me results, so even a link to the right place to look for the answer would be appreciated. Thanks!

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  • Visual NHibernate from Slyce

    - by dotnetdev
    I found this tool Visual NHibernate at http://www.slyce.com/, but a search on here has not brought anything up for what I would have thought would have been a very popular product, in concept anyway. Has anyone used this product? Any feedback on it? Thanks

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  • Ruby on Rails: jQuery datepicker - dates between validation

    - by Jazz
    I have an app that allows a user to create new projects, and the search for them later. One of the options they have when creating a project is giving them start and end dates. At the moment all the code works properly for creating and searching on the dates, but I am now wanting to restrict what dates the user can enter. I am needing for an error to flag up when the user tries to enter an end date that is before the start date. It's really more for when the user is creating the project. Here is my code so far = Application.js //= require jquery //= require jquery_ujs //= require jquery-ui //= require jquery.ui.all //= require_tree . $(function() { $("#project_start_date").datepicker({dateFormat: 'dd-mm-yy'}); }); $(function() { $("#project_end_date").datepicker({dateFormat: 'dd-mm-yy'}); }); jQuery(function(){ jQuery('#start_date_A').datepicker({dateFormat: "dd-mm-yy"}); }); jQuery(function(){ jQuery('#start_date_B').datepicker({dateFormat: "dd-mm-yy"}); }); New View: <div class="start_date" STYLE="text-align: left;"> <b>Start Date:</b> <%= f.text_field :start_date, :class => 'datepicker', :style => 'width: 80px;' %> </div> <div class="end_date" STYLE="text-align: left;"> <b>End Date:</b> <%= f.text_field :end_date, :class => 'datepicker', :style => 'width: 80px;' %> </div> Search View: Start dates between <%= text_field_tag :start_date_A, params[:start_date_A], :style => 'width: 80px;' %> - <%= text_field_tag :start_date_B, params[:start_date_B], :style => 'width: 80px;' %></br> I tried following examples online to get this to work by doing this in the application.js file: $(function() { $("#project_start_date,#project_end_date").datepicker({dateFormat: 'dd-mm-yy'}); }); jQuery(function(){ jQuery('#start_date_A,#start_date_B').datepicker({dateFormat: "dd-mm-yy"}); }); But then the script doesn't run. I am new to rails and javascript so any help at all is appreciated. Thanks in advance. UPDATE: Don't know why my question has been voted to be closed. It's quite simple: I need an error to flag up when the user tries to enter an end date that is before the start date. How can I do that??

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  • Django logs: any tutorial to log to a file

    - by Algorist
    Hi, I am working with a django project, I haven't started. The developed working on the project left. During the knowledge transfer, it was told to me that all the events are logged to the database. I don't find the database interface useful to search for logs and sometimes they don't even log(I might be wrong). I want to know, if there is an easy tutorial that explains how to enable logging in Django with minimal configuration changes. Thank you Bala

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  • Detect winning game in nought and crosses

    - by Dennis
    I need to know the best way to detect a winning move in a game of noughts and crosses. Source code doesn't matter, I just need a example or something I can start with. The only thing I can come up with is to use loops and test every direction for every move a player makes, to search for e.g five in a row. Is there a faster and more efficient way?

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  • Why "Finalize method should not reference any other objects" ?

    - by mishal153
    I have been pondering why it is recommended that we should not release managed resources inside finalize. If you see the code example at http://msdn.microsoft.com/en-us/library/system.gc.suppressfinalize.aspx , and search for string "Dispose(bool disposing) executes in two distinct scenarios" and read that comment, you will understand what I mean. Only possibility I can think of is that it probably has something to do with the fact that it is not possible to predict when finalizer will get called. Does anyone know the right answer ? thanks, mishal

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  • Friendfeed schemaless data in MYSQL

    - by John Stewart
    I read an article around schema-less database which sounds cool. (http://bret.appspot.com/entry/how-friendfeed-uses-mysql) But what isn't clear to me is how do they run search queries on this data? Since the data is in JSON format how do we look for it?

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