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• Porting an IBXpress Interbase 6 app to the current Firebird platform, on Delphi 7?

  - by robsoft

  Just wondering if there are any gotchas to be wary of here. We have a legacy D7 app that we developed several years ago for a client, which uses IBXpress to talk to the open source Interbase 6 build. We're having a number of issues with that platform these days (very slow to connect/start-up on new hardware being the chief one) and the client has okayed spending some time/money moving the database over to Firebird. We really DON'T want to embark upon moving it to D2010 (or D2007 which would be my preference right now) as we figure that we might have to move the database layer from IBXpress to something else to best suit Firebird anyway. And at the end of the day, the client is only looking to lessen the database pain, not overhaul/upgrade/rewrite the app. Given the ancestry of Firebird, is it a fairly painless, well-understood path from IBXpress Interbase 6 to (whatever) with Firebird? We have quite a number of sprocs, triggers (and even datatypes) etc in the existing IB database already (and the client has a number of paying customers all using this platform) so we felt that going to Firebird was more likely to be a smoother move than moving to SQL Express (or another flavour of DB entirely). Note that we're not looking for 'embedded' DB advocacy - in many of our client's customers' installations, the software is used in a multi-user client-server way so keeping that kind of approach is important.

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• PHP - Database schema: version control, branching, migrations.

  - by Billiam

  I'm trying to come up with (or find) a reusable system for database schema versioning in php projects. There are a number of Rails-style migration projects available for php. http://code.google.com/p/mysql-php-migrations/ is a good example. It uses timestamps for migration files, which helps with conflicts between branches. General problem with this kind of system: When development branch A is checked out, and you want to check out branch B instead, B may have new migration files. This is fine, migrating to newer content is straight forward. If branch A has newer migration files, you would need to migrate downwards to the nearest shared patch. If branch A and B have significantly different code bases, you may have to migrate down even further. This may mean: Check out B, determine shared patch number, check out A, migrate downwards to this patch. This must be done from A since the actual applied patches are not available in B. Then, checkout branch B, and migrate to newest B patch. Reverse process again when going from B to A. Proposed system: When migrating upwards, instead of just storing the patch version, serialize the whole patch in database for later use, though I'd probably only need the down() method. When changing branches, compare patches that have been run to patches that are available in the destination branch. Determine nearest shared patch (or oldest difference, maybe) between db table of run patches and patches in destination branch by ID or hash. Could also look for new or missing patches that are buried under a number of shared patches between the two branches. Automatically merge down to the nearest shared patch, using the db table stored down() methods, and then merge up to the branche's latest patch. My question is: Is this system too crazy and/or fraught with consequences to bother developing? My experience with database schema versioning is limited to PHP autopatch, which is an up()-only system requiring filenames with sequential IDs.

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• Define DataSource bean on code

  - by Ruben Trancoso

  I would like to make a "First Access Database Setup Process" in my spring application and the only thing I can imagine as a solution would be to initialize the DataSource bean programatically. My current bean is defined as: <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="com.mysql.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/catalog" /> <property name="username" value="condominium" /> <property name="password" value="password" /> <property name="validationQuery" value="SELECT 1" /> <property name="testOnBorrow" value="true" /> <property name="defaultAutoCommit" value="false" /> <property name="maxWait" value="5000" /> </bean> but the ideal thing was to load it by myself in whenever I need it and with the parameter I define. The scenario is that the user (administrator) comes to the application at the first time and I ask him the server, port and catalog to connect. I store it in a embeeded db and next time application start, a bean can check if the parameter are set on the embedded db and load it again. Is it possible?

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• Why use SQL database?

  - by martinthenext

  I'm not quite sure stackoverflow is a place for such a general question, but let's give it a try. Being exposed to the need of storing application data somewhere, I've always used MySQL or sqlite, just because it's always done like that. As it seems like the whole world is using these databases, most of all software products, frameworks, etc. It is rather hard for a beginning developer like me to ask a question - why? Ok, say we have some object-oriented logic in our application, and objects are related to each other somehow. We need to map this logic to the storage logic, so we need relations between database objects too. This leads us to using relational database and I'm ok with that - to put it simple, our database rows sometimes will need to have references to other tables' rows. But why do use SQL language for interaction with such a database? SQL query is a text message. I can understand this is cool for actually understanding what it does, but isn't it silly to use text table and column names for a part of application that no one ever seen after deploynment? If you had to write a data storage from scratch, you would have never used this kind of solution. Personally, I would have used some 'compiled db query' bytecode, that would be assembled once inside a client application and passed to the database. And it surely would name tables and colons by id numbers, not ascii-strings. In the case of changes in table structure those byte queries could be recompiled according to new db schema, stored in XML or something like that. What are the problems of my idea? Is there any reason for me not to write it myself and to use SQL database instead?

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• Avoid the problem with BigDecimal when migrating to Java 1.4 to Java 1.5+

  - by romaintaz

  Hello, I've recently migrated a Java 1.4 application to a Java 6 environment. Unfortunately, I encountered a problem with the BigDecimal storage in a Oracle database. To summarize, when I try to store a "7.65E+7" BigDecimal value (76,500,000.00) in the database, Oracle stores in reality the value of 7,650,000.00. This defect is due to the rewritting of the BigDecimal class in Java 1.5 (see here). In my code, the BigDecimal was created from a double using this kind of code: BigDecimal myBD = new BigDecimal("" + someDoubleValue); someObject.setAmount(myBD); // Now let Hibernate persists my object in DB... In more than 99% of the cases, everything works fine. Except that in really few case, the bug mentioned above occurs. And that's quite annoying. If I change the previous code to avoid the use of the String constructor of BigDecimal, then I do not encounter the bug in my uses cases: BigDecimal myBD = new BigDecimal(someDoubleValue); someObject.setAmount(myBD); // Now let Hibernate persists my object in DB... However, how can I be sure that this solution is the correct way to handle the use of BigDecimal? So my question is to know how I have to manage my BigDecimal values to avoid this issue: Do not use the new BigDecimal(String) constructor and use directly the new BigDecimal(double)? Force Oracle to use toPlainString() instead of toString() method when dealing with BigDecimal (and in this case how to do that)? Any other solution? Environment information: Java 1.6.0_14 Hibernate 2.1.8 (yes, it is a quite old version) Oracle JDBC 9.0.2.0 and also tested with 10.2.0.3.0 Oracle database 10.2.0.3.0

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• SQL Joining Two or More from Table B with Common Data in Table A

  - by Matthew Frederick

  The real-world situation is a series of events that each have two or more participants (like sports teams, though there can be more than two in an event), only one of which is the host of the event. There is an Event db table for each unique event and a Participant db table with unique participants. They are joined together using a Matchup table. They look like this: Event EventID (PK) (other event data like the date, etc.) Participant ParticipantID (PK) Name Matchup EventID (FK to Event table) ParicipantID (FK to Participant) Host (1 or 0, only 1 host = 1 per EventID) What I'd like to get as a result is something like this: EventID ParticipantID where host = 1 Participant.Name where host = 1 ParticipantID where host = 0 Participant.Name where host = 0 ParticipantID where host = 0 Participant.Name where host = 0 ... Where one event has 2 participants and another has 3 participants, for example, the third participant column data would be null or otherwise noticeable, something like (PID = ParticipantID): EventID PID-1(host) Name-1 (host) PID-2 Name-2 PID-3 Name-3 ------- ----------- ------------- ----- ------ ----- ------ 1 7 Lions 8 Tigers 12 Bears 2 11 Dogs 9 Cats NULL NULL I suspect the answer is reasonably straightforward but for some reason I'm not wrapping my head around it. Alternately it's very difficult. :) I'm using MYSQL 5 if that affects the available SQL.

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• What objects would get defined in a Bridge scoring app (Javascript)

  - by Alex Mcp

  I'm writing a Bridge (card game) scoring application as practice in javascript, and am looking for suggestions on how to set up my objects. I'm pretty new to OO in general, and would love a survey of how and why people would structure a program to do this (the "survey" begets the CW mark. Additionally, I'll happily close this if it's out of range of typical SO discussion). The platform is going to be a web-app for webkit on the iPhone, so local storage is an option. My basic structure is like this: var Team = { player1: , player2: , vulnerable: , //this is a flag for whether or //not you've lost a game yet, affects scoring scoreAboveLine: , scoreBelowLine: gamesWon: }; var Game = { init: ,//function to get old scores and teams from DB currentBid: , score: , //function to accept whether bid was made and apply to Teams{} save: //auto-run that is called after each game to commit to DB }; So basically I'll instantiate two teams, and then run loops of game.currentBid() and game.score. Functionally the scoring is working fine, but I'm wondering if this is how someone else would choose to break down the scoring of Bridge, and if there are any oversights I've made with regards to OO-ness and how I've abstracted the game. Thanks!

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• MS Access Interop - How to set print filename?

  - by Ryan

  Hi all, I'm using Delphi 2009 and the MS Access Interop COM API. I'm trying to figure out two things, but one is more important than the other right now. I need to know how to set the file name when sending the print job to the spooler. Right now it's defaulting to the Access DB's name, which can be something different than the file's name. I need to just ensure that when this is printed it enters the print spool using the same filename as the actual file itself - not the DB's name. My printer spool is actually a virtual print driver that converts documents to an image. That's my main issue. The second issue is how to specify which printer to use. This is less important at the moment because I'm just using the default printer for now. It would be nice if I could specify the printer to use, though. Does anyone know either of these two issues? Thank you in advance. I'll go ahead and paste my code: unit Converter.Handlers.Office.Access; interface uses sysutils, variants, Converter.Printer, Office_TLB, Access_TLB, UDC_TLB; procedure ToTiff(p_Printer: PrinterDriver; p_InputFile, p_OutputFile: String); implementation procedure ToTiff(p_Printer: PrinterDriver; p_InputFile, p_OutputFile: String); var AccessApp : AccessApplication; begin AccessApp := CoAccessApplication.Create; AccessApp.Visible := False; try AccessApp.OpenCurrentDatabase(p_InputFile, True, ''); AccessApp.RunCommand(acCmdQuickPrint); AccessApp.CloseCurrentDatabase; finally AccessApp.Quit(acQuitSaveNone); end; end; end.

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• Database version is zero on initial install

  - by mahesh

  I have released an app (World Time) with initial database. Now i want to update the app with a database upgrade. I have put in the upgrade code in OnUpgrade() and checking for the newVersion. But it was not being called in my local testing... So i put in the debug statement to get the database version and it is zero . Any idea why it is not being versioned ? Following is the code to copy the database from my Assets folder ... InputStream myInput = myContext.getAssets().open(DB_NAME); // Path to the just created empty db String outFileName = DB_PATH + DB_NAME; //Open the empty db as the output stream OutputStream myOutput = new FileOutputStream(outFileName); //transfer bytes from the inputfile to the outputfile byte[] buffer = new byte[1024]; int length; while ((length = myInput.read(buffer))>0){ myOutput.write(buffer, 0, length); } //Close the streams myOutput.flush(); myOutput.close(); myInput.close(); -- Mahesh http://android.maheshdixit.com

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• Making one table equal to another without a delete *

  - by Joshua Atkins

  Hey, I know this is bit of a strange one but if anyone had any help that would be greatly appreciated. The scenario is that we have a production database at a remote site and a developer database in our local office. Developers make changes directly to the developer db and as part of the deployment process a C# application runs and produces a series of .sql scripts that we can execute on the remote side (essentially delete *, insert) but we are looking for something a bit more elaborate as the downtime from the delete * is unacceptable. This is all reference data that controls menu items, functionality etc of a major website. I have a sproc that essentially returns a diff of two tables. My thinking is that I can insert all the expected data in to a tmp table, execute the diff, and drop anything from the destination table that is not in the source and then upsert everything else. The question is that is there an easy way to do this without using a cursor? To illustrate the sproc returns a recordset structured like this: TableName Col1 Col2 Col3 Dest Src Anything in the recordset with TableName = Dest should be deleted (as it does not exist in src) and anything in Src should be upserted in to dest. I cannot think of a way to do this purely set based but my DB-fu is weak. Any help would be appreciated. Apologies if the explanation is sketchy; let me know if you need anymore details.

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• Maintaining Selected Row of the DataGridView Control after refreshing Data

  - by user575219

  I am trying to Maintain Selected Row of the DataGridView Control after refreshing Data. This is my code public partial class frmPlant : Form { string gSelectedPlant; private void frmPlant_Load(object sender, EventArgs e) { dataGridView1.AutoGenerateColumns = true; dataGridView1.DataSource = bindingSource1; FillData(); dataGridView1.DataMember = "Table"; } private void FillData() { ds = _DbConnection.returnDataSet(_SQlQueries.SQL_PlantSelect); bindingSource1.DataSource = ds.Tables[0]; } public DataSet returnDataSet(string txtQuery) { conn.Open(); sqlCommand = conn.CreateCommand(); DB = new SQLiteDataAdapter(txtQuery, conn); DS.Reset(); DB.Fill(DS); conn.Close(); return (DS); } private void dataGridView1_Selectionchanged(object sender, EventArgs e) { if (dataGridView1.SelectedRows.Count > 0) { gSelectedPlant = dataGridView1.SelectedRows[0].Cells["PlantId"].Value.ToString(); } } private void dataGridView1_DataBindingComplete(object sender, DataGridViewBindingCompleteEventArgs e) { int selectedIndex; if (!string.IsNullOrEmpty(gSelectedPlant) && e.ListChangedType == ListChangedType.Reset) { if (ds.Tables.Count > 0) { selectedIndex = bindingSource1.Find("PlantId", gSelectedPlant); if (selectedIndex <= 0) selectedIndex = 0; dataGridView1.Rows[selectedIndex].Selected = true; } else { gSelectedPlant = string.Empty; } } } } It is still not able to maintain the rowindex of the selected row. It scrolls to row1. Here's the blog I used http://www.makhaly.net/Blog/9 Suppose, I select a row on Form1(where all this code is) and go on the next form, which shows me detailed info abt the particular Plant . If I come back to this first form again,by pressing the back button, the row is reset to 1. gSelectedPlant takes a value 1 and selectedindex = 0. This makes sense but I am not yet able to figure out how to maintain the value of gSelectedPlant. Yes it takes a null intitally but on databindingcomplete it becomes 1.

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• Self-referencing tables in Linq2Sql

  - by J-Man

  Hi, I've seen a lot of questions on self-referencing tables in Linq2Sql and how to eagerly load all child records for a particular root object. I've implemented a temporary solution by accessing all underlying properties, but you can see that this doesn't do the performance any good. The thing is though, that all records are correlated with each-other using a correlation GUID. Example below: RootElement - Id: 1 - ParentId: null - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement1 - Id: 2 - ParentId: 1 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement2 - Id: 3 - ParentId: 2 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD ChildElement1 - Id: 4 - ParentId: 2 - CorrelationId: 4D68E512-4B55-44f4-BA5A-174B630A03DD In my case, I do have access to the correlationId, so I can retrieve all of my records by performing the following query: from element in db.Elements where element.CorrelationId == '4D68E512-4B55-44f4-BA5A-174B630A03DD' select element; But, of course, I want these elements associated with each other by executing this query: from element in db.Elements where element.CorrelationId == '4D68E512-4B55-44f4-BA5A-174B630A03DD' && element.ParentId == null select element; My question is: is it possible to combine the results the first query as some sort of 'caching mechanism' for the query where I get the root element? Thanks for the input. J.

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• Perl - MySQL connection problem in windows

  - by dexter

  I have two folders php and perl they contain index.php and index.pl respectivly in index.pl my perl code looks like: #!/usr/bin/perl use Mysql; print "Content-type: text/html\n\n"; print "<h2>PERL-mySQL Connect</h2>"; print "page info"; $host = "localhost"; $database = "cdcol"; $user = "root"; $password = ""; $db = Mysql->connect($host, $database, $user, $password); $db->selectdb($database); when i run above code (ie type: http://localhost:88/perl/ in browser) following error comes Error message: Can't locate Mysql.pm in @INC (@INC contains: C:/xampp/perl/site/lib/ C:/xampp/perl/lib C:/xampp/perl/site/lib C:/xampp/apache) at C:/xampp/htdocs/perl/index.pl line 2. BEGIN failed--compilation aborted at C:/xampp/htdocs/perl/index.pl line 2. while this works: in browser http://localhost:88/php/ where index.php has: <?php $con = mysql_connect("localhost","root",""); if($con) { if(mysql_select_db("cdcol", $con)) { $sql="SELECT Id From products"; if(mysql_query($sql)) { $result = mysql_query($sql); if ($result)............

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• Ruby custom class to and from YAML;

  - by Sanarothe

  Hi. I'm having trouble deserializing a ruby class that I wrote to YAML. Where I want to be I want to be able to pass one object around as a full 'question' which includes the question text, some possible answers (For multi. choice) and the correct answer. One module (The encoder) takes input, builds a 'question' class out of it and appends it to the question pool. Another module reads a question pool and builds an array of 'question' objects. Where I am currently Sample Question Pool --- | --- !ruby/object:MultiQ a: "no" answer: "no" b: "no" c: "no" d: "no" text: "yes?" Encoder dump to YAML file. Object is a MultiQ filled up with input. (See below.) def dump(file, object) File.open(file, 'a') do |out| YAML.dump(object.to_yaml, out) end object = nil end MultiQ Class definition class MultiQ attr_accessor :text, :answer, :a, :b, :c, :d def initialize(text, answer, a, b, c, d) @text = text @answer = answer @a = a @b = b @c = c @d = d end end The decoder (I've been trying different things, so what's here wasn't my first or best guess. But I'm at a loss and the documentation doesn't really explain things thoroughly enough.) File.open( "test_set.yaml" ) do |yf| YAML.load_documents( yf ) { |item| new = YAML.object_maker( MultiQ, item) puts new } end Questions you can answer How do I achieve my goal? What methods should I use, between parsing, loading files or documents, to successfully deserialize a Ruby class? I've already looked over the YAML Rdoc, and I didn't absorb very much, so please don't just link me to it. What other methods would you suggest using? Is there a better way to store questions like this? Should I be using document db, relational db, xml? Some other format?

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• Using wildcards in prepared statement - MySQLi

  - by Michael Irwin

  Hi! I'm trying to run the following query, and I'm having trouble with the wildcard. function getStudents() { global $db; $users = array(); $query = $db->prepare("SELECT id, adminRights FROM users WHERE classes LIKE ? && adminRights='student'"); $query->bind_param('s', '%' . $this->className . '%'); $query->execute(); $query->bind_result($uid, $adminRights); while ($query->fetch()) { if (isset($adminRights[$this->className]) && $adminRights[$this->className] == 'student') $users[] = $uid; } $query->close(); return $users; } I'm getting an error that states: Cannot pass parameter 2 by reference. The reason I need to use the wildcard is because the column's data contains serialized arrays. I guess, if there's an easier way to handle this, what could I do? Thanks in advance!

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• PDO bindparam not working.

  - by jim

  I am trying to save data into a database using PDO. All columns save correctly with the exception of one. No matter what I try, I cannot get the data to go in. myfunc($db, $data) { echo $data; // <----- Outputs my data. example: 'jim jones' $stmt = $db->prepare("CALL test(:id, :data, :ip, :expires)"); $stmt->bindParam(':id', $id, PDO::PARAM_STR); $stmt->bindParam(':data', $data, PDO::PARAM_STR); $stmt->bindParam(':ip', $ip, PDO::PARAM_STR); $stmt->bindParam(':expires', $expires, PDO::PARAM_STR); ... } So even after verifying that the data variable in fact holds my data, the bindParam method will not bind. When I echo the data variable, I can see the data is there. It will not save though. If I copy the echo'd output of the data variable to screen and paste it into a new variable, it WILL save. I'm at this now for a couple of hours. Can someone please have a look? EDIT: I want to also mention that I have tried using bindValue() in place of bindParam() and the data for the data variable will still not save.

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• LINQ to SQL and DataPager

  - by Jonathan S.

  I'm using LINQ to SQL to search a fairly large database and am unsure of the best approach to perform paging with a DataPager. I am aware of the Skip() and Take() methods and have those working properly. However, I'm unable to use the count of the results for the datapager, as they will always be the page size as determined in the Take() method. For example: var result = (from c in db.Customers where c.FirstName == "JimBob" select c).Skip(0).Take(10); This query will always return 10 or fewer results, even if there are 1000 JimBobs. As a result, the DataPager will always think there's a single page, and users aren't able to navigate across the entire result set. I've seen one online article where the author just wrote another query to get the total count and called that. Something like: int resultCount = (from c in db.Customers where c.FirstName == "JimBob" select c).Count(); and used that value for the DataPager. But I'd really rather not have to copy and paste every query into a separate call where I want to page the results for obvious reasons. Is there an easier way to do this that can be reused across multiple queries? Thanks.

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• Shouldn't prepared statements be much faster?

  - by silversky

  $s = explode (" ", microtime()); $s = $s[0]+$s[1]; $con = mysqli_connect ('localhost', 'test', 'pass', 'db') or die('Err'); for ($i=0; $i<1000; $i++) { $stmt = $con -> prepare( " SELECT MAX(id) AS max_id , MIN(id) AS min_id FROM tb "); $stmt -> execute(); $stmt->bind_result($M,$m); $stmt->free_result(); $rand = mt_rand( $m , $M ).'<br/>'; $res = $con -> prepare( " SELECT * FROM tb WHERE id >= ? LIMIT 0,1 "); $res -> bind_param("s", $rand); $res -> execute(); $res->free_result(); } $e = explode (" ", microtime()); $e = $e[0]+$e[1]; echo number_format($e-$s, 4, '.', ''); // and: $link = mysql_connect ("localhost", "test", "pass") or die (); mysql_select_db ("db") or die ("Unable to select database".mysql_error()); for ($i=0; $i<1000; $i++) { $range_result = mysql_query( " SELECT MAX(`id`) AS max_id , MIN(`id`) AS min_id FROM tb "); $range_row = mysql_fetch_object( $range_result ); $random = mt_rand( $range_row->min_id , $range_row->max_id ); $result = mysql_query( " SELECT * FROM tb WHERE id >= $random LIMIT 0,1 "); } defenitly prepared statements are much more safer but also every where it says that they are much faster BUT in my test on the above code I have: - 2.45 sec for prepared statements - 5.05 sec for the secon example What do you think I'm doing wrong? Should I use the second solution or I should try to optimize the prep stmt?

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• sp_addlinkedserver on sql server 2005 giving problem

  - by Jit

  I am trying to create a link server of a remote database(both the servers are SQL serve2005). I am able to connect that remote server from my SQL Server management studio. I used the following syntax to create it. EXEC sp_addlinkedserver @server = N'LINKSQL2005', @srvproduct = N'', @provider = N'SQLNCLI', @provstr = N'SERVER=IP Address of remote server ;User ID=XXXXXX;Password=***' I have provided the IP addressntax. and user name and password in the above syntax. The link server is getting created. But when I try to execute a query on it I get the error below. Query Used. select * from LINKSQL2005.<DBName>.dbo.<TableName> OLE DB provider "SQLNCLI" for linked server "LINKSQL2005" returned message "Communication link failure". Msg 10054, Level 16, State 1, Line 0 TCP Provider: An existing connection was forcibly closed by the remote host. Msg 18456, Level 14, State 1, Line 0 Login failed for user 'sa'. OLE DB provider "SQLNCLI" for linked server "LINKSQL2005" returned message "Invalid connection string attribute". Pls help me, where am I making mistake.

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• Binding a date string parameter in an MS Access PDO query

  - by harryg

  I've made a PDO database class which I use to run queries on an MS Access database. When querying using a date condition, as is common in SQL, dates are passed as a string. Access usually expects the date to be surrounded in hashes however. E.g. SELECT transactions.amount FROM transactions WHERE transactions.date = #2013-05-25#; If I where to run this query using PDO I might do the following. //instatiate pdo connection etc... resulting in a $db object $stmt = $db->prepare('SELECT transactions.amount FROM transactions WHERE transactions.date = #:mydate#;'); //prepare the query $stmt->bindValue('mydate', '2013-05-25', PDO::PARAM_STR); //bind the date as a string $stmt->execute(); //run it $result = $stmt->fetch(); //get the results As far as my understanding goes the statement that results from the above would look like this as binding a string results in it being surrounded by quotes: SELECT transactions.amount FROM transactions WHERE transactions.date = #'2013-05-25'#; This causes an error and prevents the statement from running. What's the best way to bind a date string in PDO without causing this error? I'm currently resorting to sprintf-ing the string which I'm sure is bad practise. Edit: if I pass the hash-surrounded date then I still get the error as below: Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[22018]: Invalid character value for cast specification: -3030 [Microsoft][ODBC Microsoft Access Driver] Data type mismatch in criteria expression. (SQLExecute[-3030] at ext\pdo_odbc\odbc_stmt.c:254)' in C:\xampp\htdocs\ips\php\classes.php:49 Stack trace: #0 C:\xampp\htdocs\ips\php\classes.php(49): PDOStatement-execute() #1 C:\xampp\htdocs\ips\php\classes.php(52): database-execute() #2 C:\xampp\htdocs\ips\try2.php(12): database-resultset() #3 {main} thrown in C:\xampp\htdocs\ips\php\classes.php on line 49

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• Movies recommendation engine conceptual database design

  - by Supyxy

  I am working at an movie recommendations engine and i'm facing a DB design issue. My actual database looks like this: MOVIES [ID,TITLE] KEYWORDS_TABLE [ID,KEY_ID] - where ID is Foreign Key for MOVIES.id and KEY_ID is a key for a text keywords table This is not the entire DB, but i showed here what's important for my problem. I have about 50,000 movies and about 1,3 milion keywords correlations, and basically my algorithm consists in extracting all the who have the same keywords with a given movie, then ordering them by the number of keywords correlations. For example i looked for a movie similar to 'Cast away' and it returned 'Six days and six nights' because it had the most keywords correlations (4 keywords): Island Airplane crash Stranded Pilot The algorithm is based on more factors, but this one is the most important and the most difficult for the approach. Basically what i do now is getting all the movies that have at least one keyword similar to the given movie and then ordering them by other factors which are not important for a moment. There wouldn't be any problem if there weren't so many records, a query lasts in many cases up to 10-20 seconds and some of them return even over 5000 movies. Someone already helped me on here (thanks Mark Byers) with optimizing the query but that's not enough because it takes too longer SELECT DISTINCT M.title FROM keywords_table K1 JOIN keywords_table K2 ON K2.key_id = K1.key_id JOIN movies M ON K2.id = M.id WHERE K1.id = 4 So i thought it would be better if i pre-made those lists with movies recommendations for each movie, but i'm not sure how to design the tables.. whatever is it a good idea or how would you take this approach?

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• Interfaces with structs, by reference using Generics

  - by Fraga

  I can't pass by reference an interface with a struct in it, what am I doing wrong? Here is the example code: class Processor<T> where T : new() { public Processor() { Data = new T(); } public T Data; } class PeriodsProcessor : Processor<Periods> { public PeriodsProcessor() { DataBase DB = new DataBase(); Console.WriteLine(Data.Value); DB.ModifyData<Period>(Data); Console.WriteLine(Data.Value); Console.ReadLine(); } } public class Period { public string Name; } public interface IDataTable<T> { string Value { get; set; } T Filter { get; set; } } [Serializable] public struct Periods : IDataTable<Period> { public string Value { get; set; } public Period Filter { get; set; } } public class DataBase { public void ModifyData<T>(IDataTable<T> data) where T : new() { data.Value = "CHANGE"; } } class Program { static void Main(string[] args) { PeriodsProcessor PeriodsProcessor = new PeriodsProcessor(); } }

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• JPA/Hibernate query with class name?

  - by Petteri Hietavirta

  In this example com.test.Cat extends com.test.Animal and there is no field DB in CAT table of com.test.Cat explicitly defining its type (it wasn't me). When I query my animals from DB I get a collection of Animals. It is possible to sort them by class name: order by r.class but is there a way to use class name as a criteria? For example I would like to get all animals expect dogs. But no luck - even this does not work: where r.class = ? (String "ccc.test.Cat") as I get an exception: Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer at org.hibernate.type.IntegerType.set(IntegerType.java:64) at org.hibernate.type.NullableType.nullSafeSet(NullableType.java:154) at org.hibernate.type.NullableType.nullSafeSet(NullableType.java:136) at org.hibernate.param.PositionalParameterSpecification.bind(PositionalParameterSpecification.java:62) at org.hibernate.loader.hql.QueryLoader.bindParameterValues(QueryLoader.java:514) at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1589) at org.hibernate.loader.Loader.doQuery(Loader.java:696) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259) at org.hibernate.loader.Loader.doList(Loader.java:2228) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2125) at org.hibernate.loader.Loader.list(Loader.java:2120) at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:361) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1148) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:67)

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• IPhone SDK - Leaking Memory with performSelectorInBackground

  - by Steblo

  Hi. Maybe someone can help me with this strange thing: If a user clicks on a button, a new UITableView is pushed to the navigation controller. This new view is doing some database querying which takes some time. Therefore I wanted to do the loading in background. What works WITHOUT leaking memory (but freezes the screen until everything is done): WorkController *tmp=[[WorkController alloc] initWithStyle:UITableViewStyleGrouped]; self.workController=tmp; [tmp release]; [self.workController loadList]; // Does the DB Query [self.workController pushViewController:self.workController animated:YES]; Now I tried to do this: // Show Wait indicator .... WorkController *tmp=[[WorkController alloc] initWithStyle:UITableViewStyleGrouped]; self.workController=tmp; [tmp release]; [self performSelectorInBackground:@selector(getController) withObject:nil]; } -(void) getController { [self.workController loadList]; // Does the DB Query [self.navigationController pushViewController:self.workController animated:YES]; } This also works but is leaking memory and I don't know why ! Can you help ? By the way - is it possible for an App to get into AppStore with a small memory leak ? Or will this be checked first of all ? Thanks in advance !

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• Help needed in grokking password hashes and salts

  - by javafueled

  I've read a number of SO questions on this topic, but grokking the applied practice of storing a salted hash of a password eludes me. Let's start with some ground rules: a password, "foobar12" (we are not discussing the strength of the password). a language, Java 1.6 for this discussion a database, postgreSQL, MySQL, SQL Server, Oracle Several options are available to storing the password, but I want to think about one (1): Store the password hashed with random salt in the DB, one column Found on SO and elsewhere is the automatic fail of plaintext, MD5/SHA1, and dual-columns. The latter have pros and cons MD5/SHA1 is simple. MessageDigest in Java provides MD5, SHA1 (through SHA512 in modern implementations, certainly 1.6). Additionally, most RDBMSs listed provide methods for MD5 encryption functions on inserts, updates, etc. The problems become evident once one groks "rainbow tables" and MD5 collisions (and I've grokked these concepts). Dual-column solutions rest on the idea that the salt does not need to be secret (grok it). However, a second column introduces a complexity that might not be a luxury if you have a legacy system with one (1) column for the password and the cost of updating the table and the code could be too high. But it is storing the password hashed with a random salt in single DB column that I need to understand better, with practical application. I like this solution for a couple of reasons: a salt is expected and considers legacy boundaries. Here's where I get lost: if the salt is random and hashed with the password, how can the system ever match the password? I have theory on this, and as I type I might be grokking the concept: Given a random salt of 128 bytes and a password of 8 bytes ('foobar12'), it could be programmatically possible to remove the part of the hash that was the salt, by hashing a random 128 byte salt and getting the substring of the original hash that is the hashed password. Then re hashing to match using the hash algorithm...??? So... any takers on helping. :) Am I close?

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