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• Mysterious constraints problem with SQL Server 2000

  - by Ramon

  Hi all I'm getting the following error from a VB NET web application written in VS 2003, on framework 1.1. The web app is running on Windows Server 2000, IIS 5, and is reading from a SQL server 2000 database running on the same machine. System.Data.ConstraintException: Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints. at System.Data.DataSet.FailedEnableConstraints() at System.Data.DataSet.EnableConstraints() at System.Data.DataSet.set_EnforceConstraints(Boolean value) at System.Data.DataTable.EndLoadData() at System.Data.Common.DbDataAdapter.FillFromReader(Object data, String srcTable, IDataReader dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) at System.Data.Common.DbDataAdapter.FillFromCommand(Object data, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataSet dataSet) The problem appears when the web app is under a high load. The system runs fine when volume is low, but when the number of requests becomes high, the system starts rejecting incoming requests with the above exception message. Once the problem appears, very few requests actually make it through and get processed normally, about 2 in every 30. The vast majority of requests fail, until a SQL Server restart or IIS reset is performed. The system then start processing requests normally, and after some time it starts throwing the same error. The error occurs when a data adapter runs the Fill() method against a SELECT statement, to populate a strongly-typed dataset. It appears that the dataset does not like the data it is given and throws this exception. This error occurs on various SELECT statements, acting on different tables. I have regenerated the dataset and checked the relevant constraints, as well as the table from which the data is read. Both the dataset definition and the data in the table are fine. Admittedly, the hardware running both the web app and SQL Server 2000 is seriously outdated, considering the numbers of incoming requests it currently receives. The amount of RAM consumed by SQL Server is dynamically allocated, and at peak times SQL Server can consume up to 2.8 GB out of a total of 3.5 GB on the server. At first I suspected some sort of index or database corruption, but after running DBCC CHECKDB, no errors were found in the database. So now I'm wondering whether this error is a result of the hardware limitations of the system. Is it possible for SQL Server to somehow mess up the data it's supposed to pass to the dataset, resulting in constraint violation due to, say, data type/length mismatch? I tried accessing the RowError messages of the data rows in the retrieved dataset tables but I kept getting empty strings. I know that HasErrors = true for the datatables in question. I have not set the EnableConstraints = false, and I don't want to do that. Thanks in advance. Ray

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• Mapping one to one foreign key relationships in Entity Framework 4.0?

  - by John K.

  Hello all, I'm sure I'm missing something very simple, but let's say I have two entities, Employee and EmployeeType. Employee type would contain values like 'Full time', 'Contractor', 'Intern', etc. An Employee entity would contain one, and only one EmployeeType value. So I am designing a new .edmx model using the Model-First approach and generating my actual sql server data schema from the model. I want to add an integer type foreign key id into my Employee entity, EmployeeTypeId, which will map to the primary key of the EmployeeType entity. So I've gone ahead and done that in my Employee entity. Where I'm stuck is how, though the Entity Framework designer, to enforce the 1:1 referential constraint on that EmployeeTypeId property? Or does the EF handle that automatically behind the scenes? thanks in advance, John

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• Is there a more expressive way of executing SQL query using Qt?

  - by ShaChris23

  I currently have this code: // Construct query QString const statement = QString("drop database if exists %1") .arg(databaseName_); QSqlQuery query(db); query.exec(statement); Is there a better way to code than the above? Specifically, I dont like how I use QString for SQL statement. It'd be nice if Qt has some class so that I could do something like: // Construct query QSomeClass statement = "drop database if exists %1"; statement.setArg(1, databaseName_); // Replace all %1 in the original string. QSqlQuery query(db); query.exec(statement);

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• Is it possible to dynamically set a static string during compile?

  - by LonnieBest

  I'm trying to dynamically create a connection string during compile time: public static string ConnectionString { get { string connectionString = @"Data Source=" + myLibrary.common.GetExeDir() + @"\Database\db.sdf;"; return connectionString; } } I keep running into type initialisation errors. I was trying to avoid having to set the connection string for all applications that user my code library. The location of the database is different for each project that uses the library. I have code that can determine the correction string, but was wanting run it during compile time. Is this even possible?

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• SQL Server Import table keeping default values

  - by Chrissi

  I am importing a table from one database to another in SQL Server 2008 by right-clicking the target database and choosing Tasks Import Data... When I import the table I get the column names and types and all the data fine, but I lose the primary key, identity specifications and all the default values that were set in the source table. So now I have to set all the default values for each column again manually. Is there any way to get the default values with the import, or even after with a Query? I am VERY new to this and flailing in the dark, so forgive me if this is a really stupid question...

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• How to get data type property values using SPARQL

  - by udayalkonline

  hey, I have created some sample ontology in protege.According to my ontology there is a class called person and which has sub class called Student.There are some student individuals(john,paul,marry,...). I have diffiend some data property called "email" and assigned their email addresses. Following query which is resulting all the individuals in ontology.But I want to get each individual and their email address. String queryStr = "PREFIX rdfs: http://www.w3.org/2000/01/rdf-schema# "+ "PREFIX rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns# "+ "select ?ind "+ "where { "+ "?ind rdf:type http://www.semanticweb.org/ontologies/2010/5/Ontology1275975684120.owl#Student ;"+ "}\n "; Above query was tested on jena in eclipse IDE. any idea..? Thank in advance!

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• ASP.NET MVC 2: Deserialize SPROC Response

  - by dcolumbus

  I need to ask a general question. I don't have the code in front of me because I'm writing this on my iPhone. I have a Class that represents a certain XML schema. I have a SPROC that returns this XML. What I need to do is deserialize the XML to this Class. XML: <xml> <person> <firstName>Bob</firstName> <lastName>Robby</lastName> </person> </xml> I need to deserialize this XML into the custom Person Class so I can loop through this Model and spit it out in the View. I'm sure there's some kind of casting involved, I just don't know how to do it.

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• Possible Performance Considerations using Linq to SQL Repositories

  - by Robert Harvey

  I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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• .Remove(object) on a List<T> returned from LINQ to SQL compiled query won't delete the Object right

  - by soldieraman

  I am returning two lists from the database using LINQ to SQL compiled query. While looping the first list I remove duplicates from the second list as I dont want to process already existing objects again. eg. //oldCustomers is a List returned by my Compiled Linq to SQL Statmenet that I have added a .ToList() at the end to //Same goes for newCustomers for (Customer oC in oldCustomers) { //Do some processing newCustomers.Remove(newCusomters.Find(nC=> nC.CustomerID == oC.CusomterID)); } for (Cusomter nC in newCustomers) { //Do some processing } DataContext.SubmitChanges() I expect this to only save the changes that have been made to the customers in my processing and not Remove or Delete any of my customers from the database. Correct? I have tried it and it works fine - but I am trying to know if there is any rare case it might actually get removed

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• building a web application in eclipse

  - by Noona

  As a concluding assignment for the technologies taught in a data management course, we have to write a web application using the technologies taught throughout the course, this mostly includes xhtml, css, JSP, servelets, JDBC, AJAX, webservices. the project will eventually be deployed using tomcat. we are given the option of choosing the technologies that we see fit. since this is my first time developing a web application I am having some uncertainties about where to start, so for example now I am writing the object classes that will be used in the database and implementing the operations that will be performed on the database, but I am not sure about how to make these operations available to a client through the website, I mean I think I have to write a servlet through which I can extract the request parameters and set the response accordingly, but I would still like a more specific overview of what I am going to do, so if someone can link me to a tutorial with an example that makes use of these technologies while illustrating the stages of the design so that I can see how all these things are linked together in a web project. thanks

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• Encoding issue with form and HTML Purifier / MySQL

  - by Andrew Heath

  Driving me nuts... Page with form is encoded as Unicode (UTF-8) via: <meta http-equiv="content-type" content="text/html; charset=utf-8"> entry column in database is text utf8_unicode_ci copying text from a Word document with " in it, like this: “1922.” is insta-fail and ends up in the database as â??1922.â?? (typing new data into the form, including " works fine... it's cut and pasting from Word...) PHP steps behind the scenes are: grab value from POST run through HTML Purifier default settings run through mysql_real_escape_string insert query into dbase Help?

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• java.util.Date.toString() is printing out wrong format

  - by pacoverflow

  The following code prints out "vmtDataOrig.creationdate=2012-11-03" VmtData vmtDataOrig = VmtDataDao.getInstance().loadVmt(1); System.out.println("vmtDataOrig.creationdate=" + vmtDataOrig.getCreationDate().toString()); Here is the definition of the creationDate field in the VmtData class: private Date creationDate = null; Here is the hibernate mapping of the creationDate field to the database table column: <property name="creationDate" column="CREATIONDATE" type="date"/> The CREATIONDATE column in the MySQL database table is of type "date", and for the record retrieved it has the value "2012-11-03". The Javadoc for the java.util.Date.toString() method says it is supposed to print the Date object in the form "dow mon dd hh:mm:ss zzz yyyy". Anyone know why it is printing it out in the form "yyyy-MM-dd"?

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• How to know if a detached JPA entity has already been persisted or not ?

  - by snowflake

  I have a JPA entity instance in the web UI layer of my application. I'd like to know at anytime if this entity has been already persisted in database or if it is only present in the user session. It would be in the business layer, I would use entitymanager.contains(Entity) method, but in my UI layer I think I need an extra attribute indicating whether the entity has been saved or not. How implement that ? I'm considering following option for the moment: - a JPA attribute with a default value set by the database, but would force a new read after each update ? - a non JPA attribute manually set in my code or automatically set by JPA? Any advice / other suggestions ? I'm using JPA 1 with Hibernate 3.2 implementation and would prefer stick to the standard.

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• Iphone & Web App synch

  - by Jack Welsh

  I am trying to build an Iphone App client for our CRM solution so our sales people would be able to access the information available in our CRM through an Iphone App. I am trying to find out what is the recommended approach to architect the application when it comes to the database. I am not sure where should the data reside, should I save a subset of the data on the iPhone, or should I just rely on webservices and pull the information I need from the database whenever I need it. Also, is there any best practices or frameworks to build such applications on the Iphone.

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• MongoDB efficient dealing with embedded documents

  - by Sebastian Nowak

  I have serious trouble finding anything useful in Mongo documentation about dealing with embedded documents. Let's say I have a following schema: { _id: ObjectId, ... data: [ { _childId: ObjectId // let's use custom name so we can distinguish them ... } ] } What's the most efficient way to remove everything inside data for particular _id? What's the most efficient way to remove embedded document with particular _childId inside given _id? What's the performance here, can _childId be indexed in order to achieve logarithmic (or similar) complexity instead of linear lookup? If so, how? What's the most efficient way to insert a lot of (let's say a 1000) documents into data for given _id? And like above, can we get O(n log n) or similar complexity with proper indexing? What's the most efficient way to get the count of documents inside data for given _id?

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• How to create temporary files on the client machine, from Web Application?

  - by Gaurav Srivastava

  I am creating a Web Application using JSP, Struts, EJB and Servlets. The Application is a combined CRM and Accounting Package so the Database size is very huge. So, in order to make Execution faster, I want prevent round trips to the Database. For that purpose, what I want to do is create some temporary XML files on the client Machine and use them whenever required. How can I do this, as Javascript do not permits me to do so. Is there any way of doing this? Or, is there any other solution which I can adopt in order to make my application Faster?

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• Problem with datagridvieew in vb.net

  - by user225269

  I'm trying to add a datagridview in vb.net, but it does not allow me to change the connection string or the database that should be imported to connect to it. The only thing that I'm seeing is the previous ms sql database that I connected with datagridview and everytime I click the new connection, the window closes and it leaves me with the datagridview with the previous connection that I have. And its not applicable because, now I want to connect it with mysql. Not ms sql. Its some sort of a cache like feature in vb.net, how do I get rid of it. so that I can add the new connection for mysql? Do I need to reinstall visual studio 2008?

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• Using XSD file in VS2005

  - by xt_20

  Hello all I want to write an XML file. I have created an XSD file named XMLSchema.xsd, and run the command 'xsd /c XMLSchema.xsd' which generated a c# class file. Now, how do I use this file to generate XML files? Part of my code: <?xml version="1.0" encoding="utf-8"?> <xs:schema id="XMLSchema" targetNamespace="http://tempuri.org/XMLSchema.xsd" elementFormDefault="qualified" xmlns="http://tempuri.org/XMLSchema.xsd" > <xs:element name="root"> <xs:complexType> <xs:sequence> <xs:element name="Audit"> <xs:complexType> ... which generates a c# class 'root'. How do I call 'root' from my C# web program? Thanks

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• Connection hangs after time of inactivity

  - by Sinuhe

  In my application, Spring manages connection pool for database access. Hibernate uses these connections for its queries. At first glance, I have no problems with the pool: it works correctly with concurrent clients and a pool with only one connection. I can execute a lot of queries, so I think that I (or Spring) don't leave open connections. My problem appears after some time of inactivity (sometimes 30 minutes, sometimes more than 2 hours). Then, when Hibernate does some search, it lasts too much. Setting log4j level to TRACE, I get this logs: ... 18:27:01 DEBUG nsactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate3.SessionHolder@99abd7] for key [org.hibernate.impl.SessionFactoryImpl@7d2897] bound to thread [http-8080-Processor24] 18:27:01 DEBUG HibernateTransactionManager - Found thread-bound Session [org.hibernate.impl.SessionImpl@8878cd] for Hibernate transaction 18:27:01 DEBUG HibernateTransactionManager - Using transaction object [org.springframework.orm.hibernate3.HibernateTransactionManager$HibernateTransactionObject@1b2ffee] 18:27:01 DEBUG HibernateTransactionManager - Creating new transaction with name [com.acjoventut.service.GenericManager.findByExample]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT 18:27:01 DEBUG HibernateTransactionManager - Preparing JDBC Connection of Hibernate Session [org.hibernate.impl.SessionImpl@8878cd] 18:27:01 TRACE SessionImpl - setting flush mode to: AUTO 18:27:01 DEBUG JDBCTransaction - begin 18:27:01 DEBUG ConnectionManager - opening JDBC connection Here it gets frozen for about 2 - 10 minutes. But then continues: 18:30:11 DEBUG JDBCTransaction - current autocommit status: true 18:30:11 DEBUG JDBCTransaction - disabling autocommit 18:30:11 TRACE JDBCContext - after transaction begin 18:30:11 DEBUG HibernateTransactionManager - Exposing Hibernate transaction as JDBC transaction [jdbc:oracle:thin:@212.31.39.50:30998:orcl, UserName=DEVELOP, Oracle JDBC driver] 18:30:11 DEBUG nsactionSynchronizationManager - Bound value [org.springframework.jdbc.datasource.ConnectionHolder@843a9d] for key [org.apache.commons.dbcp.BasicDataSource@7745fd] to thread [http-8080-Processor24] 18:30:11 DEBUG nsactionSynchronizationManager - Initializing transaction synchronization ... After that, it works with no problems, until another period of inactivity. IMHO, it seems like connection pool returns an invalid/closed connection, and when Hibernate realizes that, ask another connection to the pool. I don't know how can I solve this problem or things I can do for delimiting it. Any help achieving this will be appreciate. Thanks. EDIT: Well, it finally was due a firewall rule. Database detects the connection is lost, but pool (dbcp or c3p0) not. So, it tries to query the database with no success. What is still strange for me is that timeout period is very variable. Maybe the rule is specially strange or firewall doesn't work correctly. Anyway, I have no access to that machine and I can only wait for an explanation. :(

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• Flashing and closing PyS60 SIS

  - by Matrich

  I created a py script for S60 2nd Edition FP3 with a background image, database, sound files which are stored in a folder on c drive. After several hours, I have managed to convert it into sis which I sent to my mobile phone. First, I installed the sis on the external memory and it failed to work. I read online that it should be on the same drive as python runtime. So I installed it on phone memory but it just flashes and then closes. I made another sis with a database and it worked so I suspect it could be because it cant find the background image and sound files in the folder. How can I know the cause of this? Also, how can I include the background image and sound files with the sis so that they are automatically installed when installing the sis file?

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• How to perform COUNT() or COUNT(*)

  - by ninumedia

  I have a list of tags in a database. Ex: villan hero spiderman superman superman I wanted to obtain a sorted list of the tag names in ascending order and the number of times the unique tag appeared in the database. I wrote this code: Ex: SELECT hashtag.tag_name, COUNT( * ) AS number FROM hashtag GROUP BY hashtag.tag_name ORDER BY hashtag.tag_name ASC This yields the correct result: hero - 1 spiderman - 1 superman - 2 villan - 1 How can I obtain the full COUNT of this entire list. The answer should be 4 in this case because there are naturally 4 rows. I can't seem to get a correct COUNT() without the statement failing. Thanks so much for the help! :)

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• Small methods - Small sprocs

  - by Berlioz

  Uncle Bob recommends having small methods. Do stored procedures have an ideal size? Or can they run on for 100's and 100's of lines long? Also does anyone have anything to say about where to place business logic. If located in stored procedures, the database is being used as data processing tier. If you read Adam Machanic, his bias is toward the database, does that imply long stored procedures that only the author of the sproc understands, leaving maintainers to deal with the mess? I guess there is two inter-related questions, somehow. Thanks in advance for responding to a fuzzy question(s).

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• Counting the most tagged tag with MySQL

  - by Jack W-H

  Hi folks My problem is that I'm trying to count which tag has been used most in a table of user-submitted code. But the problem is with the database structure. The current query I'm using is this: SELECT tag1, COUNT(tag1) AS counttag FROM code GROUP BY tag1 ORDER BY counttag DESC LIMIT 1 This is fine, except, it only counts the most often occurence of tag1 - and my database has 5 tags per post - so there's columns tag1, tag2, tag3, tag4, tag5. How do I get the highest occurring tag value from all 5 columns in one query? Jack

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• Is a class that is hard to unit test badly designed?

  - by Extrakun

  I am now doing unit testing on an application which was written over the year, before I started to do unit-testing diligently. I realized that the classes I wrote are hard to unit test, for the following reasons: Relies on loading data from database. Which means I have to setup a row in the table just to run the unit test (and I am not testing database capabilities). Requires a lot of other external classes just to get the class I am testing to its initial state. On the whole, there don't seem to be anything wrong with the design except that it is too tightly coupled (which by itself is a bad thing). I figure that if I have written automated test cases with each of the class, hence ensuring that I don't heap extra dependencies or coupling for the class to work, the class might be better designed. Does this reason holds water? What are your experiences?

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• MySQL script to delete data in chunks until everything lower then id has been deleted

  - by Chriswede

  I need an MySQL Skript which does the following: delete chunks of the database until it has deleted all link_id's greater then 10000 exmaple: x = 10000 DELETE FROM pligg_links WHERE link_id > x and link_id < x+10000 x = x + 10000 ... So it would delete DELETE FROM pligg_links WHERE link_id > 10000 and link_id < 20000 then DELETE FROM pligg_links WHERE link_id > 20000 and link_id < 30000 until all id's less then 10000 have been removed I need this because the database is very very big (more then a gig) thank in advance

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