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  • A Tale of Identifiers

    Identifiers aren't locators, and they aren't pointers or links either. They are a logical concept in a relational database, and, unlike the more traditional methods of accessing data, don't derive from the way that data gets stored. Identifiers uniquely identify members of the set, and it should be possible to validate and verify them. Celko somehow involves watches and taxi cabs to illustrate the point.

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  • Write SQL Code for MySQL Using HeidiSQL 4

    HeidiSQL is a free GUI client for MySQL, favored by many Web developers and database administrators of small to medium-sized businesses to manage persistent storage of data. This article will familiarize you with HeidiSQL&#146;s Query editor by using it to write a query that will join four tables together to perform searches against a help library.

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  • Should I use multiple column primary keys or add a new column?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • State Transition Constraints

    Data Validation in a database is a lot more complex than seeing if a string parameter really is an integer. A commercial world is full of complex rules for sequences of procedures, of fixed or variable lifespans, Warranties, commercial offers and bids. All this requires considerable subtlety to prevent bad data getting in, and if it does, locating and fixing the problem. Joe Celko shows how useful a State transition graph can be, and how essential it can become with the time aspect added.

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  • Reliable Storage Systems for SQL Server

    By validating the IO path before commissioning the production database system, and performing ongoing validation through page checksums and DBCC checks, you can hopefully avoid data corruption altogether, or at least nip it in the bud. If corruption occurs, then you have to take the right decisions fast to deal with it. Rod Colledge explains how a pessimistic mindset can be an advantage

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  • Supporting Large Scale Team Development

    With a large-scale development of a database application, the task of supporting a large number of development and test databases, keeping them up to date with different builds can soon become ridiculously complex and costly. Grant Fritchey demonstrates a novel solution that can reduce the storage requirements enormously, and allow individual developers to work on thir own version, using a full set of data.

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  • Warning: PDOStatement::execute(): SQLSTATE[HY093]: Invalid parameter number: number of bound variabl

    - by Thomas
    Hi, I'm working with PHP PDO and I have the following problem: Warning: PDOStatement::execute(): SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens in /var/www/site/classes/enterprise.php on line 63 Here is my code: public function getCompaniesByCity(City $city, $options = null) { $database = Connection::getConnection(); if(empty($options)) { $statement = $database-prepare("SELECT * FROM empresas WHERE empresas.cidades_codigo = ?"); $statement-bindValue(1, $city-getId()); } else { $sql = "SELECT * FROM empresas INNER JOIN prods_empresas ON prods_empresas.empresas_codigo = empresas.codigo WHERE "; foreach($options as $option) { $sql .= 'prods_empresas.produtos_codigo = ? OR '; } $sql = substr($sql, 0, -4); $sql .= ' AND empresas.cidades_codigo = ?'; $statement = $database-prepare($sql); echo $sql; foreach($options as $i = $option) { $statement-bindValue($i + 1, $option-getId()); } $statement-bindValue(count($options), $city-getId()); } $statement-execute(); $objects = $statement-fetchAll(PDO::FETCH_OBJ); $companies = array(); if(!empty($objects)) { foreach($objects as $object) { $data = array( 'id' = $object-codigo, 'name' = $object-nome, 'link' = $object-link, 'email' = $object-email, 'details' = $object-detalhes, 'logo' = $object-logo ); $enterprise = new Enterprise($data); array_push($companies, $enterprise); } return $companies; } } Thank you very much!

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  • NoSQL vs Ehcache caching advise for speeding up read only mysql Database

    - by paddydub
    I'm building a Route Planner Webapp using Spring/Hibernate/Tomcat and a mysql database, I have a database containing read only data, such as Bus Stop Coordinates, Bus times which is never updated. I'm trying to make the app run faster, each time the application is run it will preform approx 1000 reads to the database to calculate a route. I have setup a Ehcache which greatly improves the read from database times. I'm now setting terracotta + Ehcache distributed caching to share the cache with multiple Tomcat JVMs. This seems a bit complicated. I've tried memcached but it was not performing as fast as ehcache. I'm wondering if a MongoDb or Redis would be better suited. I have no experience with nosql but I would appreciate if anyone has any ideas. What i need is quick access to the read only database.

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  • datagrid filter in c# using sql server

    - by malou17
    How to filter data in datagrid for example if u select the combo box in student number then input 1001 in the text field...all records in 1001 will appear in datagrid.....we are using sql server private void button2_Click(object sender, EventArgs e) { if (cbofilter.SelectedIndex == 0) { string sql; SqlConnection conn = new SqlConnection(); conn.ConnectionString = "Server= " + Environment.MachineName.ToString() + @"\; Initial Catalog=TEST;Integrated Security = true"; SqlDataAdapter da = new SqlDataAdapter(); DataSet ds1 = new DataSet(); ds1 = DBConn.getStudentDetails("sp_RetrieveSTUDNO"); sql = "Select * from Test where STUDNO like '" + txtvalue.Text + "'"; SqlCommand cmd = new SqlCommand(sql, conn); cmd.CommandType = CommandType.Text; da.SelectCommand = cmd; da.Fill(ds1); dbgStudentDetails.DataSource = ds1; dbgStudentDetails.DataMember = ds1.Tables[0].TableName; dbgStudentDetails.Refresh(); } else if (cbofilter.SelectedIndex == 1) { //string sql; //SqlConnection conn = new SqlConnection(); //conn.ConnectionString = "Server= " + Environment.MachineName.ToString() + @"\; Initial Catalog=TEST;Integrated Security = true"; //SqlDataAdapter da = new SqlDataAdapter(); //DataSet ds1 = new DataSet(); //ds1 = DBConn.getStudentDetails("sp_RetrieveSTUDNO"); //sql = "Select * from Test where Name like '" + txtvalue.Text + "'"; //SqlCommand cmd = new SqlCommand(sql,conn); //cmd.CommandType = CommandType.Text; //da.SelectCommand = cmd; //da.Fill(ds1); // dbgStudentDetails.DataSource = ds1; //dbgStudentDetails.DataMember = ds1.Tables[0].TableName; //ds.Tables[0].DefaultView.RowFilter = "Studno = + txtvalue.text + "; dbgStudentDetails.DataSource = ds.Tables[0]; dbgStudentDetails.Refresh(); } }

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  • Validate MVC 2 form using Data annotations and Linq-to-SQL, before the model binder kicks in (with D

    - by Stefanvds
    I'm using linq to SQL and MVC2 with data annotations and I'm having some problems on validation of some types. For example: [DisplayName("Geplande sessies")] [PositiefGeheelGetal(ErrorMessage = "Ongeldige ingave. Positief geheel getal verwacht")] public string Proj_GeplandeSessies { get; set; } This is an integer, and I'm validating to get a positive number from the form. public class PositiefGeheelGetalAttribute : RegularExpressionAttribute { public PositiefGeheelGetalAttribute() : base(@"\d{1,7}") { } } Now the problem is that when I write text in the input, I don't get to see THIS error, but I get the errormessage from the modelbinder saying "The value 'Tomorrow' is not valid for Geplande sessies." The code in the controller: [HttpPost] public ActionResult Create(Projecten p) { if (ModelState.IsValid) { _db.Projectens.InsertOnSubmit(p); _db.SubmitChanges(); return RedirectToAction("Index"); } else { SelectList s = new SelectList(_db.Verbonds, "Verb_ID", "Verb_Naam"); ViewData["Verbonden"] = s; } return View(); } What I want is being able to run the Data Annotations before the Model binder, but that sounds pretty much impossible. What I really want is that my self-written error messages show up on the screen. I have the same problem with a DateTime, which i want the users to write in the specific form 'dd/MM/yyyy' and i have a regex for that. but again, by the time the data-annotations do their job, all i get is a DateTime Object, and not the original string. So if the input is not a date, the regex does not even run, cos the data annotations just get a null, cos the model binder couldn't make it to a DateTime. Does anyone have an idea how to make this work?

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  • LINQ-to-SQL: How can I prevent 'objects you are adding to the designer use a different data connecti

    - by Timothy Khouri
    I am using Visual Studio 2010, and I have a LINQ-to-SQL DBML file that my colleagues and I are using for this project. We have a connection string in the web.config file that the DBML is using. However, when I drag a new table from my "Server Explorer" onto the DBML file... I get presented with a dialog that demands that do one of these two options: Allow visual studio to change the connection string to match the one in my solution explorer. Cancel the operation (meaning, I don't get my table). I don't really care too much about the debate as why the PMs/devs who made this tool didn't allow a third option - "Create the object anyway - don't worry, I'm a developer!" What I am thinking would be a good solution is if I can create a connection in the Server Explorer - WITHOUT A WIZARD. If I can just paste a connection string, that would be awesome! Because then the DBML designer won't freak out on me :O) If anyone knows the answer to this question, or how to do the above, please lemme know!

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  • Cannot login to Postgrest database despite setting password for user 'postgres'

    - by Serg
    I'm trying to use pgAdmin III to manage my Postgres database. Here are the commands I've run on my machine: sudo apt-get install postgresql Then I installed the pgAdmin III application: sudo apt-get install pgadmin3 Next I focused on setting my username and password in order to login: sudo -u postgres psql postgres Here I set my password \password postgres Finally I just created my database: sudo -u postgres createdb repairsdatabase When I try to login using pgAdmin III, I get the error: An error has occurred: Error connecting to the server: FATAL: Peer authentication failed for user "postgres"

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  • MongoDb vs Ehcache caching advise for speeding up read only mysql Database

    - by paddydub
    I'm building a Route Planner Webapp using Spring/Hibernate/Tomcat and a mysql database, I have a database containing read only data, such as Bus Stop Coordinates, Bus times which is never updated. I'm trying to make the app run faster, each time the application is run it will preform approx 1000 reads to the database to calculate a route. I have setup a Ehcache which greatly improves the read from database times. I'm now setting terracotta + Ehcache distributed caching to share the cache with multiple Tomcat JVMs. This seems a bit complicated. I've tried memcached but it was not performing as fast as ehcache. I'm wondering if a MongoDb would be better suited. I have no experience with nosql but I would appreciate if anyone has any ideas. All i need is quick access to the read only database.

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  • Struts2 example, not inserting records in mysql database because connection object is getting null

    - by Jugal
    This Code is working fine with simple application so the drivers are fine. so why the connection object is not able to initialise with drivers. import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; import com.opensymphony.xwork2.ActionSupport; public class Insert extends ActionSupport { public String execute() throws Exception, SQLException { String sql = ""; String url = "jdbc:mysql://localhost:3306/test"; //String dbName = "test"; String driverName = "org.gjt.mm.mysql.Driver"; String userName = "root"; String password = "root"; Connection con=null; Statement stmt=null; try { Class.forName(driverName).newInstance(); con = DriverManager.getConnection(url, userName, password); stmt = con.createStatement(); } catch (Exception e) { System.out.println(e.getMessage()); } }

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  • Google Gears - Database - VACUUM

    - by Sirber
    With this code: var db = google.gears.factory.create('beta.database'); db.open('cominar'); db.execute('CREATE TABLE IF NOT EXISTS Ajax (AJAX_ID INTEGER PRIMARY KEY AUTOINCREMENT , MODULE TEXT, FUNCTION TEXT, CONTENT_JSON TEXT);'); db.execute('VACUUM;'); // nettoye la DB I'm trying to clean the database (VACUUM) the database at each initialisation but I get this error: Uncaught Error: Database operation failed. ERROR: authorization denied DETAILS: not authorized The database was created by me (the same page). Thank you!

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  • How can I export images from MS SQL Server to a file on disk?

    - by rball
    I have a User table that has all of their avatars saved in an image field. I'd like to just take that out of the database and store it as a regular file on disk. I looked around and saw some code for textcopy, but that doesn't seem to be on my machine for some reason. Here is the code I wrote up anyway. Anyone know a way to get this done? DECLARE @exec_str varchar (255) SELECT @exec_str = 'textcopy /S (local)\SQLEXPRESS' + --' /U ' + @login + --' /P ' + @password + ' /D thedatabase' + ' /T User'+ ' /C AvatarImage' + ' /F "d:\Avatars\' + User.Name + '.jpg"' + ' /O' FROM [User] WHERE UserID = 2 EXEC master..xp_cmdshell @exec_str

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  • Index was outside the bounds of the array. IndexOutOfRangeException in LINQ to SQL

    - by gtas
    Im getting this exception in the protected virtual void SendPropertyChanged(String propertyName) { if ((this.PropertyChanged != null)) { this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); <---- HERE !!! } } of one recently table association i created, there lots of same associations around the database, and this happened in the 4 specific tables i added. Its 1...* relationship and association is Primary Table - Id (identity auto generated) Foreign PId column int not null. I just dont get it....Im using SqlMetal for generation, i regenerated the schema, rebuild, same. This is causing while inserting row in DevExpress XtraGrid, but i dont think this should be issue, same control with same functionality but for different tables works ok. I use grid's event for append value in a property when the entity creating. I disabled this but same again. Recreated the association. No change, exception occurs. Any ideas?

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  • How do continuously update data to an asp page?

    - by Lori
    Hi, I have an asp page based on a very simple database. It references a single table of probably 30 records and maybe 12 data fields and everything works great as I am only uploading a new database every week or so. I have a special circumstance where I would like upload new data to the database and display automatically on the page every 20 to 30 seconds without the user having to refresh their screen. I would expect up to 1000 concurrent users accessing the data. I have been manually uploading the database via ftp, which will obviously not work on this timeline and would also run the risk of error pages as the database is being replaced. So, can anyone point me the right direction to setup this scenario? Other details that might be helpful: The database is an Access database (but I could change to another format if needed) Running on Windows platform hosted by an ISP, not my own server Thanks in advance for any help on this! Lori

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  • VB.net Debug sqldatareader - immediate window

    - by ScaryJones
    Scenario is this; I've a sqldatareader query that seems to be returning nothing when I try to convert the sqldatareader to a datatable using datatable.load. So I debug into it, I grab the verbose SQL query before it goes into the sqldatareader, just to make sure it's formatted correctly. I copy and paste this into SQL server to run it and see if it returns anything. It does, one row. I go back to visual studio and let the program continue, I create a datatable and try to load the sqldatareader but it just returns an empty reader. I'm baffled as to what's going on. I'll copy a version of the code (not the exact SQL query I'm using but close) here: Dim cn As New SqlConnection cn.ConnectionString = <connection string details here> cn.Open() Dim sqlQuery As String = "select * from Products where productid = 5" Dim cm As New SqlCommand(sqlQuery, cn) Dim dr As SqlDataReader = cm.ExecuteReader() Dim dt as new DataTable dt.load(dr) dt should have contents but it's empty. If I copy that SQL query into sql server and run it I get a row of results. Any ideas what I'm doing wrong? ######### UPDATE ############ I've now noticed that it seems to be returning one less row than I get with each SQL query. So, if I run the SQL myself and get 1 row then the datatable seems to have 0 rows. If the query returns 4 rows, the datatable has 3!! Very strange, any ideas anyone?

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  • sql database connection on remote server

    - by arti pathak
    i create my web site on asp.net and i create database in sql using inbuilt it in visual studio i use step to create database 1.right click on solution explorer then add newSqldatabase then ok then if i connect it by coding then it will work on my local PC but actuall i am making website so i want to store it on my web server then if i load databse file (.mdf) file in my web server where my all files are loaded then it is showing it error "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)" so please help me and send me all step how i create database and what coding i use to connect on remote server....... Thank You......

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  • SQL: How to select rows from a table while ignoring the duplicate field values?

    - by Maxxon
    How to select rows from a table while ignoring the duplicate field values? Here is an example: id user_id message 1 Adam "Adam is here." 2 Peter "Hi there this is Peter." 3 Peter "I am getting sick." 4 Josh "Oh, snap. I'm on a boat!" 5 Tom "This show is great." 6 Laura "Textmate rocks." What i want to achive is to select the recently active users from my db. Let's say i want to select the 5 recently active users. The problem is, that the following script selects Peter twice. mysql_query("SELECT * FROM messages ORDER BY id DESC LIMIT 5 "); What i want is to skip the row when it gets again to Peter, and select the next result, in our case Adam. So i don't want to show my visitors that the recently active users were Laura, Tom, Josh, Peter, and Peter again. That does not make any sense, instead i want to show them this way: Laura, Tom, Josh, Peter, (skipping Peter) and Adam. Is there an SQL command i can use for this problem?

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  • PHP/MySQL database connection priority?

    - by Josh
    Hello, I have a production database where usage statistics for a service we're working on. I use php to periodically roll up different resolutions (day, week, month, year) of interesting statistics in buckets dictated by the resolution. The php application I've written "completes" its data when its run, such that it will calculate all the rolled-up statistics for the resolutions and periods since it was last run. This is useful if we want to turn this off to debug database performance issues, because I can turn it back on and have it complete its data set. The problem I have, is the calculations are fairly intensive and drive the QPS of the production database server up. Is there a way to set a "priority" on a particular database connection so that it will only use "off-cycles" to do these calculations? Maybe a proper response would be to replicate the tables I'm working on into a different stats database, but, unfortunately I don't have the resources in place to attempt such a thing (yet). Thanks in advance for any help, Josh

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  • Setting up nHibernate with an Oracle database and Visual Studio 2010

    - by Geoff
    I'm creating a .ASPNET project and I would like to setup nHibernate as my ORM tool. I will be using an existing oracle database and Visual Studio 2010. ORM tools are very new to me and really could use any advice to better understand the tool and the process required to implement them. I've been following an article at http://nhforge.org/wikis/howtonh/your-first-nhibernate-based-application.aspx to learn about it and am stuck where they say to create a local database as mine only give me the option to create a SQL server database (perhaps this a new for visual studio 2010?). Is the purpose of this database just to cache results from the live database? Thanks for your help! Geoff

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