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• Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

  - by ke3pup

  Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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• Why is it called NoSQL?

  - by beef jerky

  I've recently worked with MongoDB and learned about its schemaless design. However, I'm confused with the term NoSQL? Why is it called that? Doesn't it use SQL or SQL-like queries? I've also read from an article that the main difference lies in how data is stored. In the case of MongoDB, it's stored like JSON documents. Is this true? Also, I'm confused why I always see 'NoSQL vs relational databases'. Aren't NoSQL databases relational? I believe documents in MongoDB are still related/linked through some keys (please correct me if I'm wrong). So why is it labeled as non-relational? Thanks in advance!

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• Details of 5GB and 50GB SQL Azure databases have now been released, along with new price points

  - by Eric Nelson

  Like many others signed up to the Windows Azure Platform, I received an email overnight detailing the upcoming database size changes for SQL Azure. I know from our work with early adopters over the last 12 months that the 1GB and 10GB limits were sometimes seen as blockers, especially when migrating existing application to SQL Azure. On June 28th 2010, we will be increasing the size limits: SQL Azure Web Edition database from 1 GB to 5 GB SQL Azure Business Edition database will go from 10 GB to 50 GB Along with these changes comes new price points, including the option to increase in increments of 10GB: Web Edition: Up to 1 GB relational database = $9.99 / month Up to 5 GB relational database = $49.95 / month Business Edition: Up to 10 GB relational database = $99.99 / month Up to 20 GB relational database = $199.98 / month Up to 30 GB relational database = $299.97 / month Up to 40 GB relational database = $399.96 / month Up to 50 GB relational database = $499.95 / month Check out the full SQL Azure pricing. Related Links: http://ukazure.ning.com UK community site Getting started with the Windows Azure Platform

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• Use cases for NoSQL

  - by seengee

  NoSQL has been getting a lot of attention in the industry recently. Really interested in peoples thoughts on the best use-cases for its use over relational database storage. What should trigger a developer into thinking that particular datasets are more suited to a NoSQL solution like Redis/CouchDB/MongoDB/Cassandra etc. Would also be really interested to hear what people have ported from relational db's to NoSQL and what improvements they have seen.

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• floating exception using icc compiler

  - by Hristo

  I'm compiling my code via the following command: icc -ltbb test.cxx -o test Then when I run the program: time ./mp6 100 > output.modified Floating exception 4.871u 0.405s 0:05.28 99.8% 0+0k 0+0io 0pf+0w I get a "Floating exception". This following is code in C++ that I had before the exception and after: // before if (j < E[i]) { temp += foo(0, trr[i], ex[i+j*N]); } // after temp += (j < E[i])*foo(0, trr[i], ex[i+j*N]); This is boolean algebra... so (j < E[i]) is either going to be a 0 or a 1 so the multiplication would result either in 0 or the foo() result. I don't see why this would cause a floating exception. This is what foo() does: int foo(int s, int t, int e) { switch(s % 4) { case 0: return abs(t - e)/e; case 1: return (t == e) ? 0 : 1; case 2: return (t < e) ? 5 : (t - e)/t; case 3: return abs(t - e)/t; } return 0; } foo() isn't a function I wrote so I'm not too sure as to what it does... but I don't think the problem is with the function foo(). Is there something about boolean algebra that I don't understand or something that works differently in C++ than I know of? Any ideas why this causes an exception? Thanks, Hristo

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• Is learning the Caché database hard coming from relational databases and object oriented programming

  - by Edelcom

  I am currently running the local version of Caché on my system in order to determine if I can (and will) take on a new possible project. The current project uses Delphi 7 as a front end calling a Caché dll where the business logic is stored in the database. I have a background of Sqlserver and Firebird (and before Access and Paradox) as databases. I use Delphi 7 for 95% of my Windows development, so I know about object programming. I would like to recieve opinions from persons having used Caché and either SqlServer, Firebird or Oracle and having developed in Delphi (or C++ or C# - an object oriented language). I have read the pro's and con's from other questions, but I am not asking for this, I need input from Caché developers. Thanks in advance.

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• MySQL Relational Database Foreign Key

  - by user623879

  To learn databasing, I am creating a movie database. To associate multiple directors with a movie, I have the following schema: movie(m_ID, ....) m_director(dirID, dirName)//dirID is a autoincrement primary key m_directs(dirID, m_ID) //dirID, m_ID are set as foreign Keys in the mysql database(InnoDB engine) I have a program that connects to the db that needs to add a movie to the database. I can easily add a new entry to the movie table and the m_director table, but I am having trouble adding a entry in the m_directs table. INSERT INTO m_director (dirName) VALUES("Jason Reitman"); INSERT INTO m_directs (dirID, m_ID) VALUES(LAST_INSERT_ID(), "tt0467406"); I am using this sql statement to insert a new director and add the association to the movie. I know the primary key of the movie, but I don't know the dirID, so I use LAST_INSERT_ID() to get the last id of the director just inserted. The problem I am having is that I get the following error: MySql.Data.MySqlClient.MySqlException (0x80004005): Cannot add or update a child row: a foreign key constraint fails (`siteproducts`. `m_directs`, CONSTRAINT `m_directs_ibfk_2` FOREIGN KEY (`dirID`) REFERENCES `m_directs` (`dirID`) ON DELETE CASCADE ON UPDATE CASCADE) Any ideas?

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• Pros/Cons of document based database vs relational database

  - by damian

  I've been trying to see if I can accomplish some requirements with a document based database, in this case CouchDB. Two generic requirements: CRUD of entities with some fields which have unique index on it ecommerce web app like eBay (better description here). And I'm begining to think that a Document-based database isn't the best choice to address these requirements. Furthermore, I can´t imagine a use for a Document based database (maybe my imagination is too little). Can you explain me if I am asking pears to an elm when I try to use a Document based database for this requirements?

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• relational database: how to design this table

  - by donpal

  I'm a database newbie designing a database. I'll use SO to ask my question because it's easier to ask it on something that you can see already, but it's not the same, it will just help me understand the right approach. As you can see, there are many questions here and each can have many answers. How should I store the answers in a table? Should I store all the answers in the SAME table with a unique id (make it the key) and just a new field for the question id? What if there are 100,000 answers like there is here? Do I still store them in 1 table? What keys should I use to minimize search time when I want to search for the answers of a specific question? The database is both read and write if that makes any difference in this case.

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• WPF - 'Relational' Data in XAML Using DataContext

  - by Andy T

  Hi, Say I have a list of Employee IDs from one data source and a separate data source with a list of Employees, with their ID, Surname, FirstName, etc. Is it possible in XAML only to get the Employee's name from the second data source and display it next to the ID, using something like this (with the syntax corrected)?.. <TextBlock x:Name="EmployeeID" Text="{Binding ID}"></TextBlock> <TextBlock Grid.Column="1" DataContext="{StaticResource EmployeeList[**where ID = {Binding ID}**]}" Text="{Binding Surname}"/> I'm thinking back to my days using XML and XSLT with XPath to achieve the kind of thing shown above. Is this kind of thing possible in XAML? Or do I need to 'denormalize' the data first in code, into one consolidated list? It seems like it should be possible to do this simple task using XAML only, but I can't quite get my head around how you would switch the DataContext correctly and what the syntax would be to achieve this. Is it possible, or am I barking up the wrong tree? Thanks, AT

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• Explanation of converting exporting an XML document as a relational database using XSLT

  - by Yaaqov

  I would like to better understand the basic steps needed to a take an XML document like this Breakfast Menu... <?xml version="1.0" encoding="ISO-8859-1"?> <breakfast_menu> <food> <name>Belgian Waffles</name> <price>$5.95</price> <description>two of our famous Belgian Waffles with plenty of real maple syrup</description> <calories>650</calories> </food> <food> <name>Strawberry Belgian Waffles</name> <price>$7.95</price> <description>light Belgian waffles covered with strawberries and whipped cream</description> <calories>900</calories> </food> <food> <name>Berry-Berry Belgian Waffles</name> <price>$8.95</price> <description>light Belgian waffles covered with an assortment of fresh berries and whipped cream</description> <calories>900</calories> </food> <food> <name>French Toast</name> <price>$4.50</price> <description>thick slices made from our homemade sourdough bread</description> <calories>600</calories> </food> <food> <name>Homestyle Breakfast</name> <price>$6.95</price> <description>two eggs, bacon or sausage, toast, and our ever-popular hash browns</description> <calories>950</calories> </food> </breakfast_menu> And "export" it to say, an Access or MySQL database using XSLT, creating two joined tables: Table: breakfast_menu Field: menu_item_id Field: food_id Table: food Field: food_id Field: name Field: price Field: description Field: calories If there are online tutorials on this that you know of, I'd be interesting in learning more, as well. Thanks.

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• How do Relational Databases Work Under the Hood?

  - by Pierreten

  I've always been interested in how you can throw some SQL at at database, and it nearly instantaneously returns your results in an orderly manner without thinking about it as anything other than a black box. What is really going on? I'm pretty sure it has something to do with how values are laid out regularly in memory, similar to an array; but aside from that, I don't know much else. How is SQL parsed in a manner to facilitate all of this?

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• Usage of WCF RIA Services, where the datasource isn't a classical (relational) database

  - by Kottan

  I want (have) to write a Silverlight and (or) ASP.NET based webapplication with SAP in the backend (in other words, the datasource is no classical database) . The usage of Silverlight and ASP.NET is a precondition. Is it possible to use the WCF RIA Services (and Silverlight) where the data-source are RFCs from SAP ? Makes this sense ? If yes, how the pattern/architecture could be shortly described ? Or should I take other architectures into considerations (usage of plain WCF services, WCF data services,...) ?

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• Add a record to relational XML with C#

  - by Megawolt

  I have a XML and XSD I want to add a record to trck table with Dataset i'm also write that code but need trackListrow... how can i handle that? playListDS rec = new playListDS(); if(File.Exists(Server.MapPath("~/playlist.xml"))) rec.ReadXml(Server.MapPath("~/playlist.xml")); int id = int.Parse(rec.track.Rows[rec.track.Rows.Count - 1][0].ToString()) + 1; if (ViewState["Filename"] != null && ViewState["Cover"] != null) { playListDS.trackListRow row = new playListDS.trackListRow(); rec.track.AddtrackRow(id.ToString(), "mp3/" + ViewState["Filename"].ToString(), txtartist.Text, txtalbum.Text, txttitle.Text, txtannotation.Text, txtduration.Text, "mp3/cover" + ViewState["Cover"].ToString(), txtinfo.Text, txtlink.Text); <?xml version="1.0"?> <!-- Generated using Flame-Ware Solutions XML-2-XSD v2.0 at http://www.flame-ware.com/Products/XML-2-XSD/ --> <xs:schema id="playListDS" targetNamespace="http://tempuri.org/playListDS.xsd" xmlns:mstns="http://tempuri.org/playListDS.xsd" xmlns="http://tempuri.org/playListDS.xsd" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:msdata="urn:schemas-microsoft-com:xml-msdata" attributeFormDefault="qualified" elementFormDefault="qualified"> <xs:element name="playListDS" msdata:IsDataSet="true" msdata:UseCurrentLocale="true"> <xs:complexType> <xs:choice minOccurs="0" maxOccurs="1"> <xs:element name="trackList"> <xs:complexType> <xs:sequence> <xs:element name="track" minOccurs="0" maxOccurs="unbounded"> <xs:complexType> <xs:sequence> <xs:element name="FileID" type="xs:string" minOccurs="0" /> <xs:element name="location" type="xs:string" minOccurs="0" /> <xs:element name="creator" type="xs:string" minOccurs="0" /> <xs:element name="album" type="xs:string" minOccurs="0" /> <xs:element name="title" type="xs:string" minOccurs="0" /> <xs:element name="annotation" type="xs:string" minOccurs="0" /> <xs:element name="duration" type="xs:string" minOccurs="0" /> <xs:element name="image" type="xs:string" minOccurs="0" /> <xs:element name="info" type="xs:string" minOccurs="0" /> <xs:element name="link" type="xs:string" minOccurs="0" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:choice> </xs:complexType> </xs:element> </xs:schema> <?xml version="1.0" standalone="yes"?> <playListDS xmlns="http://tempuri.org/playListDS.xsd"> <trackList> <track> <FileID>6</FileID> <location>mp3/Gomez - See The World-1.mp3</location> <creator>Gomez</creator> <album>How We Operate</album> <title>See the World</title> <annotation>Buraya kendi yorumun gelicek bos kalabilir</annotation> <duration>243670</duration> <image>mp3/coverChrysanthemum.jpg</image> <info /> <link>Grubun bi sitesi fln varsa buraya yazabilisin yoksa beni sil</link> </track> </trackList> </playListDS>

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• What is the best PHP framework for building a website around a heavily relational PostgreSQL databas

  - by Kenaniah

  First of all, the framework of choice needs to have excellent support for PostgreSQL. I don't care about MySQL because it doesn't have half of the features the application I will be porting requires. (And when I say excellent support, I mean that their approach to database drivers has not been solely trained in MySQL). The ideal framework: Should take full advantage of PHP 5.3 and PostgreSQL 8.4 features Should support new technologies such as OpenID and social networking Should support complex relationships between database relations Should have an intelligent validation system Should have a basic library of helpful views (such as pagination, navigation, etc) Should probably be MVC based Should have excellent documentation and an active development community Should namespace classes intelligently What I'm looking for might be more of a library of utilities, as I really don't want to be restricted by the framework in what I can and can not do. I have my own small library of core classes that take care of business logic, and I will most likely want to integrate those with the new framework as well. Thanks!

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• Database: relational/not relational/object oriented... What to choose?

  - by Damian

  I'm porting a website that I made for app engine to run on a dedicated server. It is coded in java and I'm looking for a database to replace google datastore. My first thougt was MySql because everybody uses it, but i dont like SQL and I think I would feel more comfortable using OODB or anything else. With google datastore I could modify my models and don't worry about the database definition at all. I know using MySql that isn't possible. And I don't want to miss that. And if I use a OODB, which should I use? What about performance compared to MySql? Well, any idea or tip will really help me since I know nothing about databases.

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• Core Data: Multiple conditions inside relational aggregate operations

  - by Uzaak

  I have an SQLite table used by Core Data with the following elements: Name: John LastName: Foobar Age: 23 Name: Bob LastName: Baz Age: 37 Name: Peter LastName: Fooqux Age: 32 Name: John LastName: Bar Age: 29 Those are all in a to-many relationship from another object "Company". I need to query the database and retrieve all Company objects with employees called "John" but whose last name does NOT contain "Foo". I did go as far as to make the following predicate: [NSPredicate predicateWithFormat:@"ANY employee.name = 'John'"]; How do I get to filter only by companies whose Johns don't have "Foo" in their last names?

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• Drawing information from relational databases in Rails

  - by Trip

  I am trying to pull the name of the Artist from the Albums database. These are my two models class Album < ActiveRecord::Base belongs_to :artist validates_presence_of :title validates_length_of :title, :minimum => 5 end class Artist < ActiveRecord::Base has_many :albums end And here is the Albums Controller def index @ albums = Album.all respond_to do |format| format.html # index.html.erb format.xml { render :xml => @albums } end end And the View from the index: <% @albums.each do |album| %> <tr> <td><%=h album.id %></td> <td><%=h album.title %></td> <td><%=h album.artist.name %></td> </tr <% end %> My end result html is coming out like this for the artist field! # and if i set it to artist.name I get this: undefined method `name' for nil:NilClass

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• Transforming OLTP Relational Database to Data Warehousing Model

  - by Russ Cam

  What are the common design approaches taken in loading data from a typical Entity-Relationship OLTP database model into a Kimball star schema Data Warehouse/Marts model? Do you use a staging area to perform the transformation and then load into the warehouse? How do you link data between the warehouse and the OLTP database? Where/How do you manage the transformation process - in the database as sprocs, dts/ssis packages, or SQL from application code?

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• Suggestion on Database structure for relational data

  - by miccet

  Hi there. I've been wrestling with this problem for quite a while now and the automatic mails with 'Slow Query' warnings are still popping in. Basically, I have Blogs with a corresponding table as well as a table that keeps track of how many times each Blog has been viewed. This last table has a huge amount of records since this page is relatively high traffic and it logs every hit as an individual row. I have tried with indexes on the fields that are included in the WHERE clause, but it doesn't seem to help. I have also tried to clean the table each week by removing old ( 1.weeks) records. SO, I'm asking you guys, how would you solve this? The query that I know is causing the slowness is generated by Rails and looks like this: SELECT count(*) AS count_all FROM blog_views WHERE (created_at >= '2010-01-01 00:00:01' AND blog_id = 1); The tables have the following structures: CREATE TABLE IF NOT EXISTS 'blogs' ( 'id' int(11) NOT NULL auto_increment, 'name' varchar(255) default NULL, 'perma_name' varchar(255) default NULL, 'author_id' int(11) default NULL, 'created_at' datetime default NULL, 'updated_at' datetime default NULL, 'blog_picture_id' int(11) default NULL, 'blog_picture2_id' int(11) default NULL, 'page_id' int(11) default NULL, 'blog_picture3_id' int(11) default NULL, 'active' tinyint(1) default '1', PRIMARY KEY ('id'), KEY 'index_blogs_on_author_id' ('author_id') ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ; And CREATE TABLE IF NOT EXISTS 'blog_views' ( 'id' int(11) NOT NULL auto_increment, 'blog_id' int(11) default NULL, 'ip' varchar(255) default NULL, 'created_at' datetime default NULL, 'updated_at' datetime default NULL, PRIMARY KEY ('id'), KEY 'index_blog_views_on_blog_id' ('blog_id'), KEY 'created_at' ('created_at') ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

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• Data Visualization Prototype (Java/Eclipse/DAO/Relational DB)

  - by Vince

  Hello, I am building a prototype application which displays various 2D & 3D data charts. I am using a third party library for the charts, the database and data extraction layer have already been coded. Can you advise on a good desktop Framework to use within Eclipse to provide a 'professional' looking GUI with minimum coding required (This is just a prototype). Further can anyone advise an effective method to port this application to a web server so users could access remotely? I have limited experience with GWT, are their more suitable alternatives? Many Thanks

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• What are Attribute Relational Graphs ?

  - by Jack

  What kind of data structures are these? Can someone please point out any links or books where I can read more about them.

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• I Need Help Fixing My Small Time Sheet Table - Relational DB - SQL Server

  - by user327387

  I have a TimeSheet table as: CREATE TABLE TimeSheet ( timeSheetID employeeID setDate timeIn outToLunch returnFromLunch timeOut ); Employee will set his/her time sheet daily, i want to ensure that he/she doesn't cheat. What should i do? Should i create a column that gets date/time of the system when insertion/update happens to the table and then compare the created date/time with the time employee's specified - If so in this case i will have to create date/time column for timeIn, outToLunch, returnFromLunch and timeOut. I don't know, what do you suggest? Note: i'm concerned about tracking these 4 columns timeIn, outToLunch, returnFromLunch and timeOut

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• Zend DB inserting relational data

  - by Wimbjorno

  I'm using the Zend Framework database relationships for a couple of weeks now. My first impression is pretty good, but I do have a question related to inserting related data into multiple tables. For a little test application I've related two tables with each other by using a fuse table. +---------------+ +---------------+ +---------------+ | Pages | | Fuse | | Prints | +---------------+ +---------------+ +---------------+ | pageid | | fuseid | | printid | | page_active | | fuse_page | | print_title | | page_author | | fuse_print | | print_content | | page_created | | fuse_locale | | ... | | ... | | ... | +---------------+ +---------------+ +---------------+ Above is an example of my DB architecture Now, my problem is how to insert related data to two separate tables and insert the two newly created ID's into the fuse table at the same time. If someone could could maybe explain or give me a topic related tutorial. I would appreciate it!

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• Designing Relational Survey Questionnaires Database

  - by user1213055

  I'm trying to build a simple sql database for following access database. Currently there is no relationship and I just have two tables male and female with 6 sections in each form. How can I design it a better way so end user can connect to the database and analyze using STATA or SPSS ? I'm really confused whether I should create one table with all fields or break down into different tables. The database is specific to this study only so I'm not looking for a generic survey database where user can create surveys and capture them. Any feedback or suggestion is much appreciated.

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