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  • Joining Tables Based on Foreign Keys

    - by maestrojed
    I have a table that has a lot of fields that are foreign keys referencing a related table. I am writing a script in PHP that will do the db queries. When I query this table for its data I need to know the values associated with these keys not the key. How do most people go about this? A 101 way to do this would be to query this table for its data including the foreign keys and then query the related tables to get each key's value. This could be a lot of queries (~10). Question 1: I think I could write 1 query with a bunch of joins. Would that be better? This approach also requires the querying script to know which table fields are foreign keys. Since I have many tables like this but all with different fields, this means writing nice generic functions is hard. MySQL InnoDB tables allow for foreign constraints. I know the database has these set up correctly. Question 2: What about the idea of querying the table and identifying what the constraints are and then matching them up using whatever process I decide on from Question 1. I like this idea but never see it being used in code. Makes me think its not a good idea for some reason. I would use something like SHOW CREATE TABLE tbl_name; to find what constraints/relationships exist for that table. Thank you for any suggestions or advice.

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  • A table that has relation to itself issue

    - by Mostafa
    Hi , I've defined table with this schema : CREATE TABLE [dbo].[Codings]( [Id] [int] IDENTITY(1,1) NOT NULL, [ParentId] [int] NULL, [CodeId] [int] NOT NULL, [Title] [nvarchar](50) COLLATE Arabic_CI_AI NOT NULL, CONSTRAINT [PK_Codings] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] And fill it up with data like this : Id ParentId CodeId Title ----------- ----------- ----------- ---------- 1 NULL 0 Gender 2 1 1 Male 3 1 2 Female 4 NULL 0 Educational Level 5 4 1 BS 6 4 2 MS 7 4 3 PHD Now , I'm looking for a solution , in order , When i delete a record that is parent ( like Id= 1 or 4 ), It delete all child automatically ( all records that their ParentId is 1 or 4 ) . I supposed i can do it via relation between Id and Parent Id ( and set cascade for delete rule ) , But when i do that in MMS , the Delete Rule or Update Rule in Properties is disabled . My question is , What can i do to accomplish this ? Thank you

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  • Cover flow model in iphone

    - by abdulsamad
    I am making the cover flow model on the iPhone using the tutorial found here: http://www.chaosinmotion.com/flowcover.m I want to move the cover flow animation up in the screen at height of about 150, but when I change the starting y point of the rectangle, then my image is cut off from the top. How can I prevent this?

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  • c#3.5 Deserialization error - object reference not set

    - by BBR
    I am trying to deserialize an xml string in c#3.5, the code below does work in c# 4.0. When I try to run in the code in c#3.5 I get an Object reference not set to an instance of an object exception when the code tries in initialize the XmlSerializer. Any help would be appreciated. string xml = "<boolean xmlns=\"http://schemas.microsoft.com/2003/10/serialization/\">false</boolean>"; var xSerializer = new XmlSerializer(typeof(bool), null, null, new XmlRootAttribute("boolean"), "http://schemas.microsoft.com/2003/10/serialization/"); using (var sr = new StringReader(xml)) using (var xr = XmlReader.Create(sr)) { var y = xSerializer.Deserialize(xr); } System.NullReferenceException was unhandled Message="Object reference not set to an instance of an object." Source="System.Xml" StackTrace: at System.Xml.Serialization.XmlSerializer..ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, String defaultNamespace, String location, Evidence evidence) at System.Xml.Serialization.XmlSerializer..ctor(Type type, XmlAttributeOverrides overrides, Type[] extraTypes, XmlRootAttribute root, String defaultNamespace) .... at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException:

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  • How to use OCL constraints to prevent node creation in an GMF generated editor

    - by TheMorph
    Hello, I am working on editors created with GMF and struggling with OCL right now. Is there a possibilty to prevent a node to be created if an OCL statement in the mapping evaluates to false? If tried adding an OCL statement to a node and all it does is making the node not visible in the editor, but it is created. There is also an OCL statement in the ecore file, but this way it is only evaluated when there should be something done with the created model. I does not prevent a user to construct an invalid model but this is what I intend to prevent. Thanks in advance, Morph

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  • JAVA - Strange problem (probably thread problem) with JTable & Model

    - by Stefanos Kargas
    I am using 2 Tables (JTable) with their DefaultTableModels. The first table is already populated. The second table is populated for each row of the first table (using an SQL Query). My purpose is to export every line of the first table with it's respective lines of the second in an Excel File. I am doing it with a for (for each line of 1st table), in which I write a line of the 1st table in the Excel File, then I populate the 2nd table (for this line of 1st Table), I get every line from the Table (from it's Model actually) and put it in the Excel File under the current line of 1st table. This means that if I have n lines in first table I will clear and populate again the second table n times. All this code is called in a seperate thread. THE PROBLEM IS: Everything works perfectly fine ecxept that I am getting some exceptions. The strange thing is that I'm not getting anything false in my result. The Excel file is perfect. Some of the lines of the exceptions are: Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0 = 0 at java.util.Vector.elementAt(Vector.java:427) at javax.swing.table.DefaultTableModel.getValueAt(DefaultTableModel.java:632) at javax.swing.JComponent.paint(JComponent.java:1017) at javax.swing.RepaintManager.paint(RepaintManager.java:1220) at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:803) I am assuming that the problem lies in the fact that the second table needs some more time to be populated before I try to get any data from it. That's why I see RepaintManager and paintDirtyRegions in my exceptions. Another thing I did is that I ran my program in debug mode and I put a breakpoint after each population of the 2nd table. Then I pressed F5 to continue for each population of 2nd table and no exception appeared. The program came to it's end without any exceptions. This is another important fact that tells me that maybe in this case I gave the table enough time to be populated. Of course you will ask me: If your program works fine, why do you care about the exceptions? I care for avoiding any future problems and I care to have a better understanding of Java and Java GUI and threads. Why do you depend on a GUI component (and it's model) to get your information and why don't you recreate the resultset that populates your tables using an SQL Query and get your info from the resultset? That would be the best and the right way. The fact is that I have the tables code ready and it was easier for me to just get the info from them. But the right way would be to get everything direct from database. Anyway what I did brought out my question, and answering it would help me understand more things about java. So I posted it.

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  • window.setInterval from inside an object

    - by Keith Rousseau
    I'm currently having an issue where I have a javascript object that is trying to use setInterval to call a private function inside of itself. However, it can't find the object when I try to call it. I have a feeling that it's because window.setInterval is trying to call into the object from outside but doesn't have a reference to the object. FWIW - I can't get it to work with the function being public either. The basic requirement is that I may need to have multiple instances of this object to track multiple uploads that are occurring at once. If you have a better design than the current one or can get the current one working then I'm all ears. The following code is meant to continuously ping a web service to get the status of my file upload: var FileUploader = function(uploadKey) { var intervalId; var UpdateProgress = function() { $.get('someWebService', {}, function(json) { alert('success'); }); }; return { BeginTrackProgress: function() { intervalId = window.setInterval('UpdateProgress()', 1500); }, EndTrackProgress: function() { clearInterval(intervalId); } }; }; This is how it is being called: var fileUploader = new FileUploader('myFileKey'); fileUploader.BeginTrackProgress();

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  • processing json objects in jsp

    - by user98534
    i have a JSON object sent from the browser to the jsp page. how do i receive that object and process it in jsp. do i need any specific parsers? i have used the following piece of code. but it wouldnt work. essentially i should read the contents of the object and print them in the jsp. <%@page language="java" import="jso.JSONObject"%> <% JSONObject inp=request.getParameter("param1"); %> <% for(int i=0;i<inp.size();i++) {%> <%=inp.getString(i)%> <% } %>

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  • Dictionary object syntax?

    - by posfan12
    I'm having trouble figuring out the syntax for a JScript .NET dictionary object. I have tried private var myDictionary: Dictionary<string><string>; but the compiler complains that it's missing a semicolon and that the Dictionary object is not declared. I know JScript does have a native dictionary-like object format, but I'm not sure if there are disadvantages to using it instead of the .NET-specific construct. I.e., what if someone wants to extend my script using another .NET language?

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  • c# send recive object over network?

    - by Data-Base
    Hello, I'm working on a server/client project the client will be asking the server for info and the server will send them back to the client the info may be string,number, array, list, arraylist or any other object I found allot of examples but I faced issues!!!! the solution I found so far is to serialize the object (data) and send it then de-serialize it to process here is the server code public void RunServer(string SrvIP,int SrvPort) { try { var ipAd = IPAddress.Parse(SrvIP); /* Initializes the Listener */ if (ipAd != null) { var myList = new TcpListener(ipAd, SrvPort); /* Start Listeneting at the specified port */ myList.Start(); Console.WriteLine("The server is running at port "+SrvPort+"..."); Console.WriteLine("The local End point is :" + myList.LocalEndpoint); Console.WriteLine("Waiting for a connection....."); while (true) { Socket s = myList.AcceptSocket(); Console.WriteLine("Connection accepted from " + s.RemoteEndPoint); var b = new byte[100]; int k = s.Receive(b); Console.WriteLine("Recieved..."); for (int i = 0; i < k; i++) Console.Write(Convert.ToChar(b[i])); string cmd = Encoding.ASCII.GetString(b); if (cmd.Contains("CLOSE-CONNECTION")) break; var asen = new ASCIIEncoding(); // sending text s.Send(asen.GetBytes("The string was received by the server.")); // the line bove to be modified to send serialized object? Console.WriteLine("\nSent Acknowledgement"); s.Close(); Console.ReadLine(); } /* clean up */ myList.Stop(); } } catch (Exception e) { Console.WriteLine("Error..... " + e.StackTrace); } } here is the client code that should return an object public object runClient(string SrvIP, int SrvPort) { object obj = null; try { var tcpclnt = new TcpClient(); Console.WriteLine("Connecting....."); tcpclnt.Connect(SrvIP, SrvPort); // use the ipaddress as in the server program Console.WriteLine("Connected"); Console.Write("Enter the string to be transmitted : "); var str = Console.ReadLine(); Stream stm = tcpclnt.GetStream(); var asen = new ASCIIEncoding(); if (str != null) { var ba = asen.GetBytes(str); Console.WriteLine("Transmitting....."); stm.Write(ba, 0, ba.Length); } var bb = new byte[2000]; var k = stm.Read(bb, 0, bb.Length); string data = null; for (var i = 0; i < k; i++) Console.Write(Convert.ToChar(bb[i])); //convert to object code ?????? Console.ReadLine(); tcpclnt.Close(); } catch (Exception e) { Console.WriteLine("Error..... " + e.StackTrace); } return obj; } I need to know a good serialize/serialize and how to integrate it into the solution above :-( I would be really thankful for any help cheers

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  • Immutability of big objects

    - by Malax
    Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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  • What are the reasons *not* to use a GUID for a primary key?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • OCL constraints intended prevent node creation in an GMF generated editor only makes it invisible

    - by TheMorph
    Hello, I am working on editors created with GMF and struggling with OCL right now. Is there a possibilty to prevent a node to be created if an OCL statement in the mapping evaluates to false? If tried adding an OCL statement to a node and all it does is making the node not visible in the editor, but it is created. There is also an OCL statement in the ecore file, but this way it is only evaluated when there should be something done with the created model. I does not prevent a user to construct an invalid model but this is what I intend to prevent. Thanks in advance, Morph

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  • PostgreSQL: Why does this simple query not use the index?

    - by David
    I have a table t with a column c, which is an int and has a btree index on it. Why does the following query not utilize this index? explain select c from t group by c; The result I get is: HashAggregate (cost=1005817.55..1005817.71 rows=16 width=4) -> Seq Scan on t (cost=0.00..946059.84 rows=23903084 width=4) My understanding of indexes is limited, but I thought such queries were the purpose of indexes.

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  • c# object instantiation

    - by user1112111
    What's the difference between: Object o = new Object(); o.foo(); and new Object().foo(); (assuming I do not need the reference afterwards) ? Are there any reasons for using one instead of the other one (e.g. memory usage) ?

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  • How to "uninstantiate" an object?

    - by Mark
    I wrote a function in Python: def instantiate(c): if inspect.isclass(c): return c() elif isinstance(c, object): return c else: raise Exception, '%s is not an object or class.' % c Now I want to do the opposite: get the class from an already instantiated object so that I can re-instantiate it with different parameters. How can I do that?

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  • Are GUID primary keys bad in theory, or just practice?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • What is Erlang's concurrency model actually ?

    - by arun_suresh
    I was reading a paper recently Why Events are Bad. The paper is a comparative study of Event based and thread based highly concurrent servers and finally concludes stating that Threads are better than events in that scenario. I find that I am not able to classify what sort of concurrency model erlang exposes. Erlang provides Light Weight Processes, but those processes are suspended most of the time until it has received some event/message of some sort. /Arun

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  • Comparing all properties of an object using expression trees

    - by stringargs
    Hi, I'm trying to write a simple generator that uses an expression tree to dynamically generate a method that compares all properties of an instance of a type to the properties of another instance of that type. This works fine for most properties, like int an string, but fails for DateTime? (and presumably other nullable value types). The method: static Delegate GenerateComparer(Type type) { var left = Expression.Parameter(type, "left"); var right = Expression.Parameter(type, "right"); Expression result = null; foreach (var p in type.GetProperties()) { var leftProperty = Expression.Property(left, p.Name); var rightProperty = Expression.Property(right, p.Name); var equals = p.PropertyType.GetMethod("Equals", new[] { p.PropertyType }); var callEqualsOnLeft = Expression.Call(leftProperty, equals, rightProperty); result = result != null ? (Expression)Expression.And(result, callEqualsOnLeft) : (Expression)callEqualsOnLeft; } var method = Expression.Lambda(result, left, right).Compile(); return method; } On a DateTime? property it fails with: Expression of type 'System.Nullable`1[System.DateTime]' cannot be used for parameter of type 'System.Object' of method 'Boolean Equals(System.Object)' OK, so it finds an overload of Equals that expects object. So why can't I pass a DateTime? into that, as it's convertible to object? If I look at Nullable<T>, it indeed has an override of Equals(object o). PS: I realize that this isn't a proper generator yet as it can't deal with null values, but I'll get to that :)

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  • object.jquery attribute

    - by Esteve Camps
    Hello, what does this code performs? if(object.jquery){ .... } I don't know what jQuery attribute does. I think it checks if 'object' is a valid jQuery object, but I'm not really sure. Thanks in advance. Esteve

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  • Zend Framework modular app, can't load models for each module, autoloading models?

    - by EricP
    Is there a way to have models for each module? I have 3 modules, one is a "contacts" module. I created a model for it in modules/contacts/models/Codes.php Codes Controller class Contacts_CodesController extends Zend_Controller_Action { public function init() { /* Initialize action controller here */ $this->view->messages = $this->_helper->flashMessenger->getMessages(); } public function indexAction() { $codesTable = new Contacts_Model_Codes(); } Codes Model: class Contacts_Model_Codes extends Zend_Db_Table { protected $_name = 'codes'; } The error I get: Fatal error: Class 'Contacts_Model_Codes' not found in /Applications/MAMP/htdocs/zf_site/application/modules/contacts/controllers/CodesController.php on line 26 thanks

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