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  • Display formatted text in a window using python

    - by nikolaos
    I make a program in wxpython which displays questions to the user and a radiobox with answers. Questions and answers should be in a database and is formatted text using some mathematics (paranthesis, root squares etc). Could you propose me what widget I should use for such a text and what could be the database? Thanks.

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  • If change in a directory then do some action in linux

    - by user194469
    Hi All, I want to store the file and file information into the database automatically, when any file is inserted into the directory. Let suppose, in the /etc directory, we store some log files. And if we are inserted new file into /etc directory or change any existing file then automatically these file information should be go to specific database table. How can i do that. Regards, Amit

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  • Internal class and access to external members.

    - by Knowing me knowing you
    I always thought that internal class has access to all data in its external class but having code: template<class T> class Vector { template<class T> friend std::ostream& operator<<(std::ostream& out, const Vector<T>& obj); private: T** myData_; std::size_t myIndex_; std::size_t mySize_; public: Vector():myData_(nullptr), myIndex_(0), mySize_(0) { } Vector(const Vector<T>& pattern); void insert(const T&); Vector<T> makeUnion(const Vector<T>&)const; Vector<T> makeIntersection(const Vector<T>&)const; class Iterator : public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: Iterator()//<<<<<<<<<<<<<------------COMMENT { /*HERE I'M TRYING TO USE ANY MEMBER FROM Vector<T> AND I'M GETTING ERR SAYING: ILLEGAL CALL OF NON-STATIC MEMBER FUNCTION*/} Iterator(T** ty) { itData_ = ty; } Iterator operator++() { return ++itData_; } T operator*() { return *itData_[0]; } bool operator==(const Iterator& obj) { return *itData_ == *obj.itData_; } bool operator!=(const Iterator& obj) { return *itData_ != *obj.itData_; } bool operator<(const Iterator& obj) { return *itData_ < *obj.itData_; } }; typedef Iterator iterator; iterator begin()const { assert(mySize_ > 0); return myData_; } iterator end()const { return myData_ + myIndex_; } }; See line marked as COMMENT. So can I or I can't use members from external class while in internal class? Don't bother about naming, it's not a Vector it's a Set. Thank you.

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  • Connect to SQLite Database using Eclipse (Java)

    - by bnabilos
    Hello, I'm trying to connect to SQLite database with Ecplise but I have some errors. This is my Java code and the errors that I get on output. Please see if you can help me. Thank you in advance. package jdb; import java.sql.*; public class Test { public static void main(String[] args) throws Exception { Class.forName("org.sqlite.JDBC"); Connection conn = DriverManager.getConnection("jdbc:sqlite:/Applications/MAMP/db/sqlite/test.sqlite"); Statement stat = conn.createStatement(); stat.executeUpdate("drop table if exists people;"); stat.executeUpdate("create table people (name, occupation);"); PreparedStatement prep = conn.prepareStatement( "insert into people values (?, ?);"); prep.setString(1, "Gandhi"); prep.setString(2, "politics"); prep.addBatch(); prep.setString(1, "Turing"); prep.setString(2, "computers"); prep.addBatch(); prep.setString(1, "Wittgenstein"); prep.setString(2, "smartypants"); prep.addBatch(); conn.setAutoCommit(false); prep.executeBatch(); conn.setAutoCommit(true); ResultSet rs = stat.executeQuery("select * from people;"); while (rs.next()) { System.out.println("name = " + rs.getString("name")); System.out.println("job = " + rs.getString("occupation")); } rs.close(); conn.close(); } } ans that what I get in Ecplise : Exception in thread "main" java.lang.ClassNotFoundException: org.sqlite.JDBC at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at jdb.Test.main(Test.java:7) Thank you

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  • USB windows xp final USB access issues

    - by Lex Dean
    I basically understand you C++ people, Please do not get distracted because I'm writing in Delphi. I have a stable USB Listing method that accesses all my USB devices I get the devicepath, and this structure: TSPDevInfoData = packed record Size: DWORD; ClassGuid: TGUID; DevInst: DWORD; // DEVINST handle Reserved: DWord; end; I get my ProductID and VenderID successfully from my DevicePath Lists all USB devices connected to the computer at the time That enables me to access the registry data to each device in a stable way. What I'm lacking is a little direction Is friendly name able to be written inside the connected USB Micro chips by the firmware programmer? (I'm thinking of this to identify the device even further, or is this to help identify Bulk data transfer devices like memory sticks and camera's) Can I use SPDRP_REMOVAL_POLICY_OVERRIDE to some how reset these polices What else can I do with the registry details. Identifying when some one unplugs a device The program is using (in windows XP standard) I used a documented windows event that did not respond. Can I read a registry value to identify if its still connected? using CreateFileA (DevicePath) to send and receive data I have read when some one unplugs in the middle of a data transfer its difficult clearing resources. what can IoCreateDevice do for me and how does one use it for that task This two way point of connection status and system lock up situations is very concerning. Has some one read anything about this subject recently? My objectives are to 1. list connected USB devices identify a in development Micro Controller from everything else send and receive data in a stable and fast way to the limits of the controller No lock up's transferring data Note I'm not using any service packs I understand everything USB is in ANSI when windows xp is not and .Net is all about ANSI (what a waste of memory) I plan to continue this project into a .net at a later date as an addition. MSDN gives me Structures and Functions and what should link to what ok but say little to what they get used for. What is available in my language Delphi is way over priced that it needs a major price drop.

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  • object expected - jquery

    - by fusion
    i'm getting an error 'Object expected' for some odd reason due to jquery, and this does not 'submit' the form or enter the data into database. without jquery, the data could be entered into the database. but now it doesn't. i've used jquery mainly for validating asp.net controls.

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  • C# Select clause returns system exception instead of relevant object

    - by Kashif
    I am trying to use the select clause to pick out an object which matches a specified name field from a database query as follows: objectQuery = from obj in objectList where obj.Equals(objectName) select obj; In the results view of my query, I get: base {System.SystemException} = {"Boolean Equals(System.Object)"} Where I should be expecting something like a Car, Make, or Model Would someone please explain what I am doing wrong here? The method in question can be seen here: // this function searches the database's table for a single object that matches the 'Name' property with 'objectName' public static T Read<T>(string objectName) where T : IEquatable<T> { using (ISession session = NHibernateHelper.OpenSession()) { IQueryable<T> objectList = session.Query<T>(); // pull (query) all the objects from the table in the database int count = objectList.Count(); // return the number of objects in the table // alternative: int count = makeList.Count<T>(); IQueryable<T> objectQuery = null; // create a reference for our queryable list of objects T foundObject = default(T); // create an object reference for our found object if (count > 0) { // give me all objects that have a name that matches 'objectName' and store them in 'objectQuery' objectQuery = from obj in objectList where obj.Equals(objectName) select obj; // make sure that 'objectQuery' has only one object in it try { foundObject = (T)objectQuery.Single(); } catch { return default(T); } // output some information to the console (output screen) Console.WriteLine("Read Make: " + foundObject.ToString()); } // pass the reference of the found object on to whoever asked for it return foundObject; } } Note that I am using the interface "IQuatable<T>" in my method descriptor. An example of the classes I am trying to pull from the database is: public class Make: IEquatable<Make> { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Model> Models { get; set; } public Make() { // this public no-argument constructor is required for NHibernate } public Make(string makeName) { this.Name = makeName; } public override string ToString() { return Name; } // Implementation of IEquatable<T> interface public virtual bool Equals(Make make) { if (this.Id == make.Id) { return true; } else { return false; } } // Implementation of IEquatable<T> interface public virtual bool Equals(String name) { if (this.Name.Equals(name)) { return true; } else { return false; } } } And the interface is described simply as: public interface IEquatable<T> { bool Equals(T obj); }

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  • Error while sending email to Multiple Addresses From MYSQL Database using PHP

    - by user1751581
    I am trying to send an email to multiple email addresses which are contained in a database and sorted into a recordset... The recordset has multiple columns, but I only need one: "Email". I know that if I have them in an array I can implode them and separate them by commas, but I'm not sure how I could do that with a recordset column. Anyone know how? BTW I know I have the mail function commented out... The echo is returning null... Heres the code that I tried: $colname_rsAllLeads = "-1"; if (isset($_SESSION['MM_Username'])) { $colname_rsAllLeads = $_SESSION['MM_Username']; } mysql_select_db($database_myBackOfficeConn, $myBackOfficeConn); $query_rsAllLeads = sprintf("SELECT Email FROM Leads WHERE `User` = %s ORDER BY FullName ASC", GetSQLValueString($colname_rsAllLeads, "text")); $rsAllLeads = mysql_query($query_rsAllLeads, $myBackOfficeConn) or die(mysql_error()); $row_rsAllLeads = mysql_fetch_assoc($rsAllLeads); $totalRows_rsAllLeads = mysql_num_rows($rsAllLeads); $editFormAction = $_SERVER['PHP_SELF']; if (isset($_SERVER['QUERY_STRING'])) { $editFormAction .= "?" . htmlentities($_SERVER['QUERY_STRING']); } if ((isset($_POST["MM_insert"])) && ($_POST["MM_insert"] == "form")) { $startcode = $_POST['messagefield']; $replaced = preg_replace( '/\\\\(?="|\')/', '', $startcode ); echo $replaced; $collectedleads = implode(',', $row_rsAllLeads['Email']); echo $collectedleads; /* $to = $collectedleads; $subject = $_POST['subjectfield']; $body = $replaced; $headers = "MIME-Version: 1.0\r\n"; $headers .= "Content-type: text/html; charset=iso-8859-1\r\n"; $headers .= "From: " . $row_rs_CurrentUser['FirstName'] . " " . $row_rs_CurrentUser['LastName'] . " <" . $row_rs_CurrentUser['Email'] . ">"; if (mail($to, $subject, $body, $headers)) { } else { echo("<p>Message delivery failed...</p>"); } */ $insertSQL = sprintf("INSERT INTO PendingEmails (`to`, subject, message) VALUES (%s, %s, %s)", GetSQLValueString($row_rsAllLeads['Email'], "text"), GetSQLValueString($_POST['subjectfield'], "text"), GetSQLValueString($_POST['messagefield'], "text")); mysql_select_db($database_myBackOfficeConn, $myBackOfficeConn); $Result1 = mysql_query($insertSQL, $myBackOfficeConn) or die(mysql_error()); $insertGoTo = "Email Sent.php"; if (isset($_SERVER['QUERY_STRING'])) { $insertGoTo .= (strpos($insertGoTo, '?')) ? "&" : "?"; $insertGoTo .= $_SERVER['QUERY_STRING']; } header(sprintf("Location: %s", $insertGoTo)); } When I use var_dump($row_rsAllLeads['Email']) it outputs string(16) "[email protected]" but I know that there is no error in my SQL query because when I put them in a select box, they all show up...

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  • mysql multiple insert - what happens on error?

    - by aviv
    What happens in mysql multiple records insert during an error. I have a table: id | value 2 | 100 UNIQUE(id) Now i try to execute the query: INSERT INTO table(id, value) VALUES (1,10),(2,20),(3,30) I will get a duplicate-key error for the (2,20) BUT... Will the (1,10) get into the database? Will the (3,30) get into the database?

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  • On Redirect - Failed to generate a user instance of SQL Server...

    - by Craig Russell
    Hello (this is a long post sorry), I am writing a application in ASP.NET MVC 2 and I have reached a point where I am receiving this error when I connect remotely to my Server. Failed to generate a user instance of SQL Server due to failure in retrieving the user's local application data path. Please make sure the user has a local user profile on the computer. The connection will be closed. I thought I had worked around this problem locally, as I was getting this error in debug when site was redirected to a baseUrl if a subdomain was invalid using this code: protected override void Initialize(RequestContext requestContext) { string[] host = requestContext.HttpContext.Request.Headers["Host"].Split(':'); _siteProvider.Initialise(host, LiveMeet.Properties.Settings.Default["baseUrl"].ToString()); base.Initialize(requestContext); } protected override void OnActionExecuting(ActionExecutingContext filterContext) { if (Site == null) { string[] host = filterContext.HttpContext.Request.Headers["Host"].Split(':'); string newUrl; if (host.Length == 2) newUrl = "http://sample.local:" + host[1]; else newUrl = "http://sample.local"; Response.Redirect(newUrl, true); } ViewData["Site"] = Site; base.OnActionExecuting(filterContext); } public Site Site { get { return _siteProvider.GetCurrentSite(); } } The Site object is returned from a Provider named siteProvider, this does two checks, once against a database containing a list of all available subdomains, then if that fails to find a valid subdomain, or valid domain name, searches a memory cache of reserved domains, if that doesn't hit then returns a baseUrl where all invalid domains are redirected. locally this worked when I added the true to Response.Redirect, assuming a halting of the current execution and restarting the execution on the browser redirect. What I have found in the stack trace is that the error is thrown on the second attempt to access the database. #region ISiteProvider Members public void Initialise(string[] host, string basehost) { if (host[0].Contains(basehost)) host = host[0].Split('.'); Site getSite = GetSites().WithDomain(host[0]); if (getSite == null) { sites.TryGetValue(host[0], out getSite); } _site = getSite; } public Site GetCurrentSite() { return _site; } public IQueryable<Site> GetSites() { return from p in _repository.groupDomains select new Site { Host = p.domainName, GroupGuid = (Guid)p.groupGuid, IsSubDomain = p.isSubdomain }; } #endregion The Linq query ^^^ is hit first, with a filter of WithDomain, the error isn't thrown till the WithDomain filter is attempted. In summary: The error is hit after the page is redirected, so the first iteration is executing as expected (so permissions on the database are correct, user profiles etc) shortly after the redirect when it filters the database query for the possible domain/subdomain of current redirected page, it errors out.

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  • Can't access font resource in Silverlight class library

    - by Matt
    I have a reasonably large Silveright 3.0 project on the go, and I'm having issues accessing a couple of custom font resources from within one of the assemblies. I've got a working test solution where I have added a custom font as a resource, and can access it fine from XAML using: <TextBlock Text="Test" FontFamily="FontName.ttf#Font Name" /> The test solution consists of the TestProject.Application and the TestProject.Application.Web projects, with all the fun and games obviously in the TestProject.Application project However, when I try this in my main solution, the fonts refuse to show in the correct type face (instead showing in the default font). There's no difference in the way the font has been added to project between the test solution and the main solution, and the XAML is identical. However, there is a solution layout difference. In the main solution, as well as having a MainApp.Application and MainApp.Application.Web project, I also have a MainApp.Application.ViewModel project and a MainApp.Application.Views project, and the problem piece of XAML is the in the MainApp.Application.Views project (not the .Application project like the test solution). I've tried putting the font into either the .Application or .Application.Views project, tried changing the Build Action to Content, Embedded Resource etc, all to no avail. So, is there an issue accessing font resources from a child assembly that I don't know about, or has anyone successfully done this? My long term need will be to have the valid custom fonts being stored as resources in a separate .Application.FontLibrary assembly that will be on-demand downloaded and cached, and the XAML controls in the .Application.Views project will need to reference this FontLibrary assembly to get the valid fonts. I've also tried xcreating this separate font library assembly, and I can't seem to get the fonts from the second assembly. As some additional information, I've also tried the following font referencing approaches: <TextBlock Text="Test" FontFamily="/FontName.ttf#Font Name" /> <TextBlock Text="Test" FontFamily="pack:application,,,/FontName.ttf#Font Name" /> <TextBlock Text="Test" FontFamily="pack:application,,,/MainApp.Application.Views;/FontName.ttf#Font Name" /> <TextBlock Text="Test" FontFamily="pack:application,,,/MainApp.Application.Views;component/FontName.ttf#Font Name" /> And a few similar variants with different assembly references/sub directories/random semi colons. And so far nothing works... anyone struck this (and preferably solved it)?

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  • PHP CMS with ability to create custom tables

    - by Cracker
    I am building a website. I have created the database in MySQL. I need to build the web pages really fast! Is there a PHP CMS with which I can easily create the webpages with forms that can modify my database tables? The point is that I don't want to code it using plain PHP or MVC frameworks either. I looked at other CMSs' like Drupal and Joomla but it looks like its difficult to make them use custom tables.

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  • C# Property Access vs Interface Implementation

    - by ehdv
    I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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  • Add Access-Control-Allow-Origin to header in PHP

    - by SANDeveloper
    I am trying to workaround CORS restriction on a WebGL application. I have a Web Service which resolves URL and returns images. Since this web service is not CORS enabled, I can't use the returned images as textures. I was planning to: Write a PHP script to handle image requests Image requests would be sent through the query string as a url parameter The PHP Script will: Call the web service with the query string url Fetch the image response (web service returns a content-type:image response) Add the CORS header (Add Access-Control-Allow-Origin) to the response Send the response to the browser I tried to implement this using a variety of techniques including CURL, HTTPResponse, plain var_dump etc. but got stuck at some point in each. So I have 2 questions: Is the approach good enough? Considering the approach is good enough: I made the most progress with CURL. I could get the image header and data with: $ch = curl_init(); $url = $_GET["url"]; curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_HEADER, true); curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type:image/jpeg')); //Execute request $response = curl_exec($ch); //get the default response headers $headers = curl_getinfo($ch); //close connection curl_close($ch); But this doesn't actually change set the response content-type to image/jpeg. It dumps the header + response into a new response of content-type text/html and display the header and the image BLOB data in the browser. How do I get it to send the response in the format I want? Managed to get it working: $ch = curl_init(); $url = $_GET["url"]; curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_HEADER, false); //Execute request $response = curl_exec($ch); //get the default response headers $headers = curl_getinfo($ch); curl_setopt($ch, CURLOPT_HTTPHEADER, $headers); header('Content-Type: image/jpeg'); header("Access-Control-Allow-Origin: *"); // header("Expires: Sat, 26 Jul 2017 05:00:00 GMT"); //close connection curl_close($ch); flush();

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  • delete row from selected gridview and database

    - by user175084
    i am trying to delete a row from the gridview and database... It should be deleted if a delte linkbutton is clicked in the gridview.. I am gettin the row index as follows: protected void LinkButton1_Click(object sender, EventArgs e) { LinkButton btn = (LinkButton)sender; GridViewRow row = (GridViewRow)btn.NamingContainer; if (row != null) { LinkButton LinkButton1 = (LinkButton)sender; // Get reference to the row that hold the button GridViewRow gvr = (GridViewRow)LinkButton1.NamingContainer; // Get row index from the row int rowIndex = gvr.RowIndex; string str = rowIndex.ToString(); //string str = GridView1.DataKeys[row.RowIndex].Value.ToString(); RemoveData(str); //call the delete method } } now i want to delete it... so i am having problems with this code.. i get an error Must declare the scalar variable "@original_MachineGroupName"... any suggestions private void RemoveData(string item) { SqlConnection conn = new SqlConnection(@"Data Source=JAGMIT-PC\SQLEXPRESS; Initial Catalog=SumooHAgentDB;Integrated Security=True"); string sql = "DELETE FROM [MachineGroups] WHERE [MachineGroupID] = @original_MachineGroupID; SqlCommand cmd = new SqlCommand(sql, conn); cmd.Parameters.AddWithValue("@original_MachineGroupID", item); conn.Open(); cmd.ExecuteNonQuery(); conn.Close(); } Blockquote <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:SumooHAgentDBConnectionString %>" SelectCommand="SELECT MachineGroups.MachineGroupID, MachineGroups.MachineGroupName, MachineGroups.MachineGroupDesc, MachineGroups.TimeAdded, MachineGroups.CanBeDeleted, COUNT(Machines.MachineName) AS Expr1, DATENAME(month, (MachineGroups.TimeAdded - 599266080000000000) / 864000000000) + SPACE(1) + DATENAME(d, (MachineGroups.TimeAdded - 599266080000000000) / 864000000000) + ', ' + DATENAME(year, (MachineGroups.TimeAdded - 599266080000000000) / 864000000000) AS Expr2 FROM MachineGroups FULL OUTER JOIN Machines ON Machines.MachineGroupID = MachineGroups.MachineGroupID GROUP BY MachineGroups.MachineGroupID, MachineGroups.MachineGroupName, MachineGroups.MachineGroupDesc, MachineGroups.TimeAdded, MachineGroups.CanBeDeleted" DeleteCommand="DELETE FROM [MachineGroups] WHERE [MachineGroupID] =@original_MachineGroupID" > <DeleteParameters> <asp:Parameter Name="@original_MachineGroupID" Type="Int16" /> <asp:Parameter Name="@original_MachineGroupName" Type="String" /> <asp:Parameter Name="@original_MachineGroupDesc" Type="String" /> <asp:Parameter Name="@original_CanBeDeleted" Type="Boolean" /> <asp:Parameter Name="@original_TimeAdded" Type="Int64" /> </DeleteParameters> </asp:SqlDataSource> I still get an error : Must declare the scalar variable "@original_MachineGroupID"

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  • Get column of a mysql entry

    - by Xelluloid
    Is there a possibility to get the name of the column a database entry belongs to? Perhaps I have three columns with column names col1, col2 and col3. Now I want to select for every column the column with the maximum entry, something like this. Select name_of_column(max(col1,col2,col3)). I know that I can ask for the name of the columns by its ordinal position in the information_schema.COLUMNS table but how do I get the ordinal position of a database entry within a table?

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  • SQL Insert into ... values ( SELECT ... FROM ... )

    - by Shadow_x99
    I am trying to insert into a table using the input from another table. Although this is entirely feasible for many database engines, I always seem to struggle to remember the correct syntax for the SQL-Engine of the day (MySQL, Oracle, SQLServer, Informix, DB2). I've been wondering if there is a silver-bullet syntax coming from an SQL Standards (For example, SQL92) that would allow me to insert the values without worrying about the underlying database.

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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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