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• Designing model/database for distance between any two locations (that may change)

  - by Yo Ludke

  We should create a web app which has a number of events each with a location (created as user-generated content, so the number of events will be increasingly large). The distance between any events should be available, for example to determine the top 5 closest events and such things. Users may change the locations of events. How should one design the database/model for this (in a scalable way)? I was thinking of doing it with a "distance table" (like so http://www.deutschland-tourist.info/images/entfernungstabelle.gif). Then every time, if a location changes, one row and one column have to be recalculated (this should be done with a delayed job, because it is not important to have the changes instantly). Possible problems in Scaling: Database to large (n² items for n events), too much calculation to be done. For example we should see if this is okay for 10.000 users. If each has created just one event, then this would be 100 million integers... Do you think this would be a good way to do it efficiently? How could one realize such a distance table with an rails model? Is it possible with a SQL databse? Would you start other approaches?

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• PHP/json My field names are being truncated to 30 characters. Can I stop this?

  - by Biff MaGriff

  Hi Everyone! Ok so I got this piece of vendor software that they said should be run on an apache php server and MySql database. I didn't have either of those so I put it on a PHP IIS server and I converted the code to work on SQL server. ex. mysql_select_db - mssql_select_db (among other things) So I have the following code in a php file $query = "SELECT * FROM TableName WHERE KEY_FIELD = '".$keyField."';"; $result = mssql_query($query); $arr = array(); while ( $obj = mssql_fetch_object($result) ) { $arr[] = $obj; } echo '{"results":'.json_encode($arr).'}'; and my results look something like this (captured with fiddler 2) {"results":[{"KEY_FIELD":"57", "My30characterlongfieldthatiscu":"GoodValue"}]} "My30characterlongfieldthatiscu" should be "My30characterlongfieldthatiscutoff" Kinda weird, no? The vendor claims that the app works perfectly on their end. I'm thinking this is some sort of IIS PHP limit, is there a way around it or can I expand it? I found this solution http://www.php.net/manual/en/ref.mssql.php#74834 but I don't understand it. Thanks!

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• Compare system date with a date field in SQL

  - by JeT_BluE

  I am trying to compare a date record in SQL Server with the system date. In my example the user first register with his name and date of birth which are then stored in the database. The user than logs into the web application using his name only. After logging in, his name is shown on the side where it says "Welcome "player name" using Sessions. What I am trying to show in addition to his name is a message saying "happy birthday" if his date of birth matches the system date. I have tried working with System.DateTime.Now, but what I think is that it is also comparing the year, and what I really want is the day and the month only. I would really appreciate any suggestion or help. CODE In Login page: protected void Button1_Click(object sender, EventArgs e) { String name = TextBox1.Text; String date = System.DateTime.Today.ToShortDateString(); SqlConnection myconn2 = new SqlConnection(ConfigurationManager.ConnectionStrings["User"].ToString()); SqlCommand cmd2 = new SqlCommand(); SqlDataReader reader; myconn2.Open(); cmd2 = new SqlCommand("Select D_O_B from User WHERE Username = @username", myconn2); cmd2.Parameters.Add("@username", SqlDbType.NVarChar).Value = name; cmd2.Connection = myconn2 cmd2.ExecuteNonQuery(); reader = cmd2.ExecuteReader(); while (reader.Read().ToString() == date) { Session["Birthday"] = "Happy Birthday"; } } Note: I using the same reader in the code above this one, but the reader here is with a different connection. Also, reader.Read() is different than reader.HasRows? Code in Web app Page: string date = (string)(Session["Birthday"]); // Retrieving the session Label6.Text = date;

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• WCF with MANY database connections

  - by Jorge Dominguez

  I'm working in the development of an ERP type .Net WinForms application consuming a WCF service. It's to be used by many small companies (in the range of 100-200). Database is SQL Server 2008 and the service will be hosted as a Windows service. Even thought there will be a single DB Server, our customer insists in having separate databases for each company. That is because of stability/support concerns (like DB being damaged or took offline for some reason thus affecting all clients). Concerns coming from previous experiences (not necessarily with same platform). With a single database, connections to the DB would be opened at service start up and pooling used, but, I'm not sure how connections could be managed in a multiple DB scenario: Could a connection to the corresponding DB be opened and closed for each service request? would performance be acceptable? If a connection is opened and maintained for each company accessing the system, what's the practical limit of opened connections (to different databases)? It would be very interesting to hear your opinions and suggestions for this situation. Tanks

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• Strange data swapping error occurs when I attempt to update rows in my table from another table in m

  - by Wesley

  So I have a table of data that is 10,000 lines long. Several of the columns in the table simply describe information about one of the columns, meaning, that only one column has the content, and the rest of the columns describe the location of the content (its for a book). Right now, only 6,000 of the 10,000 rows' content column is filled with its content. Rows 6-10,000's content column simply says null. I have another table in the db that has the content for rows 6,000-10,000, with the correct corresponding primary key which would (seemingly) make it easy to update the 10,000 row table. I have been trying an update query such as the following: UPDATE table(10,000) SET content_column = (SELECT content FROM table(6,000-10,000) WHERE table(10,000).id = table(6-10,000.id) Which kind of works, the only problem is that it pulls in the data from the second table just fine, but it replaces the existing content column with null. So rows 1-6,000's content column become null, and rows 6-10,000's content column have the correct values...Pretty strange I thought anyway. Does anybody have any thoughts about where I am going wrong? If you could show me a better sql query, I would appreciate it! Thanks

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• Efficient update of SQLite table with many records

  - by blackrim

  I am trying to use sqlite (sqlite3) for a project to store hundreds of thousands of records (would like sqlite so users of the program don't have to run a [my]sql server). I have to update hundreds of thousands of records sometimes to enter left right values (they are hierarchical), but have found the standard update table set left_value = 4, right_value = 5 where id = 12340; to be very slow. I have tried surrounding every thousand or so with begin; .... update... update table set left_value = 4, right_value = 5 where id = 12340; update... .... commit; but again, very slow. Odd, because when I populate it with a few hundred thousand (with inserts), it finishes in seconds. I am currently trying to test the speed in python (the slowness is at the command line and python) before I move it to the C++ implementation, but right now this is way to slow and I need to find a new solution unless I am doing something wrong. Thoughts? (would take open source alternative to SQLite that is portable as well)

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• Large scale Merge Replication strategy - what can go wrong?

  - by niidto

  Hi, I'm developing a piece of software that uses Merge Replication and SQL Compact on Windows Mobile 6. At the moment it is running on 5 devices reasonably well. The issues I've come up against are as follows: The schema has had to change a lot, and will continue to have to change as the application evolves. There have been various errors replicating these schema changes down to the device, uploads failing due to schema inconsistencies. Subscriptions expiring (after 14 days) and unable to reinitialize with upload - AKA, potential data los of unsynced data up to that point. Basically, the worst case scenario is data loss, and when merge replication fails, there seems to be no way back to get the data off. My method until now has been to drop and create the subscription on the device. I don't hear many people doing this, though it seems to solve everything. The long term plan is to role this out to 500+ devices. Any advice on people who have undertaken similar projects, and how to minimise data loss and make it so that there's appropriate error handling code to recover from sync failures would be much appreciated. James

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• Faster Insertion of Records into a Table with SQLAlchemy

  - by Kyle Brandt

  I am parsing a log and inserting it into either MySQL or SQLite using SQLAlchemy and Python. Right now I open a connection to the DB, and as I loop over each line, I insert it after it is parsed (This is just one big table right now, not very experienced with SQL). I then close the connection when the loop is done. The summarized code is: log_table = schema.Table('log_table', metadata, schema.Column('id', types.Integer, primary_key=True), schema.Column('time', types.DateTime), schema.Column('ip', types.String(length=15)) .... engine = create_engine(...) metadata.bind = engine connection = engine.connect() .... for line in file_to_parse: m = line_regex.match(line) if m: fields = m.groupdict() pythonified = pythoninfy_log(fields) #Turn them into ints, datatimes, etc if use_sql: ins = log_table.insert(values=pythonified) connection.execute(ins) parsed += 1 My two questions are: Is there a way to speed up the inserts within this basic framework? Maybe have a Queue of inserts and some insertion threads, some sort of bulk inserts, etc? When I used MySQL, for about ~1.2 million records the insert time was 15 minutes. With SQLite, the insert time was a little over an hour. Does that time difference between the db engines seem about right, or does it mean I am doing something very wrong?

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• Assigning values to the lable through database depending on listbox values

  - by SurajVitekar

  I want to assign the values of five labels from database regarding to values selected in listbox. The db query returns single column with multiple records. Please help. I'm working with C# 2010 and MS SQL. My current code is: private void listBox1_SelectedIndexChanged(object sender, EventArgs e) { try { String c1, c2; c1 = "NULL"; MessageBox.Show("LB index :"+listBox1.SelectedIndex.ToString()); //p = listBox1.SelectedItem.ToString(); SqlConnection con = new SqlConnection(); con.ConnectionString = "Data Source=localhost;Initial Catalog=eVoting;Integrated Security=True;Pooling=False"; con.Open(); MessageBox.Show("List bOx sect :"+listBox1.SelectedValue.ToString()); SqlCommand cmd = new SqlCommand("select Firstname from candidates where position ='" + listBox1.SelectedValue.ToString() + "'", con); int index = 0; SqlDataReader reader = cmd.ExecuteReader(); while(reader.Read()) { if (index == 0) { c1 = reader[index].ToString(); radioButton1.Text = c1; } if (index == 1) { c1 = reader[index].ToString(); radioButton2.Text = c1; } if (index == 2) { c1 = reader[index].ToString(); radioButton3.Text = c1; } if (index == 3) { c1 = reader[index].ToString(); radioButton4.Text = c1; } if (index == 4) { c1 = reader[index].ToString(); radioButton4.Text = c1; } if (index == 5) { c1 = reader[index].ToString(); radioButton5.Text = c1; } MessageBox.Show("c1 :" + c1); index++; } } catch (Exception E) { } }

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• How to configure an index.htm file in IIS?

  - by salvationishere

  I am running IIS 6.0 on an XP OS using VS 2008 and SQL Server 2008 (Full install). I developed two web apps. Both of these I can run from IIS by setting them to the default website. However, now I tried adding an index.htm file. Real simple; all it has is two hyperlinks to these web apps. But now only the first web app works. The first web app is pure VS. The second web app modifies an Adventureworks database table. But now when I click the hyperlink for the second web app, it gives me the error below. However this error doesn't make sense to me cause I have the two web apps configured as two virtual directories beneath C:\inetpub\ and the index.htm file is also beneath C:\inetpub. And the default website is set to home directory C:\inetpub\ with Document index.htm on top. Also, why does the first web app work and not the second now? Server Error in '/AddFileToSQL' Application. The path '/AddFileToSQL/App_GlobalResources/' maps to a directory outside this application, which is not supported. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: The path '/AddFileToSQL/App_GlobalResources/' maps to a directory outside this application, which is not supported. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

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• At what point is it worth using a database?

  - by radix07

  I have a question relating to databases and at what point is worth diving into one. I am primarily an embedded engineer, but I am writing an application using QT to interface with our controller. We are at an odd point where we have enough data that it would be feasible to implement a database (around 700+ items and growing) to manage everything, but I am not sure it is worth the time right now to deal with. I have no problems implementing the GUI with files generated from excel and parsed in, but it gets tedious and hard to track even with VBA scripts. I have been playing around with converting our data into something more manageable for the application side with Microsoft Access and that seems to be working well. If that works out I am only a step (or several) away from using an SQL database and using the QT library to access and modify it. I don't have much experience managing data at this level and am curious what may be the best way to approach this. So what are some of the real benefits of using a database if any in this case? I realize much of this can be very application specific, but some general ideas and suggestions on how to straddle the embedded/application programming line would be helpful. Thanks

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• Advice on setting up a central db with master tables for web apps

  - by Dragn1821

  I'm starting to write more and more web applications for work. Many of these web applications need to store the same types of data, such as location. I've been thinking that it may be better to create a central db and store these "master" tables there and have each applicaiton access them. I'm not sure how to go about this. Should I create tables in my application's db to copy the data from the master table and store in the app's table (for linking with other app tables using foreign keys)? Should I use something like a web service to read the data from the master table instead of firing up a new db connection in my app? Should I forget this idea and just store the data within my app's db? I would like to have data such as the location central so I can go to one table and add a new location and the next time someone needs to select a location from one of the apps, the new one would be there. I'm using ASP.NET MVC 1.0 to build the web apps and SQL 2005 as the db. Need some advice... Thanks!

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• Xml Conversion "Type mismatch" Error

  - by prema

  I am selecting a query in sql server 2005 SELECT 'Region' AS ELEMENT,(SELECT GeographyName,GeoID from @tmpTable FOR XML RAW, TYPE) FOR XML RAW('Root') This will give the output in xml as <Root ELEMENT="Region"> <row GeographyName="East" GeoID="2" /> <row GeographyName="West" GeoID="3" /> <row GeographyName="North" GeoID="4" /> <row GeographyName="South" GeoID="5" /> </Root> In aspx page, i want to get this function Populatedata(obj, val) { var xmlDom = new JXmlDom(obj, false); --> at this point i am getting error var nodeHeader = xmlDom.selectNodes("//row"); // my code goes here } function JXmlDom (xml,isFile) { this.load=load; this.loadXML=loadXML; this.selectNodes=selectNodes; this.text=text; this.selectSingleNode=selectSingleNode; this.documentElement=documentElement; this.transformNode=transformNode; if (isFile) { this.dom=this.load (xml); }else { this.dom=this.loadXML (xml); } function loadXML (xml) { if (window.ActiveXObject) { var dom=new ActiveXObject("Microsoft.XMLDOm"); dom.async=false; dom.loadXML (xml); } if (document.implementation && document.implementation.createDocument) { var domParser=new DOMParser(); var dom=domParser.parseFromString (xml,"text/xml"); } return dom; } But when i am calling this i am getting an error as Type mismatch.Can anyone help me

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• Cannot perform an ORDERBY against my EF4 data

  - by Jaxidian

  I have a query hitting EF4 using STEs and I'm having an issue with user-defined sorting. In debugging this, I have removed the dynamic sorting and am hard-coding it and I still have the issue. If I swap/uncomment the var results = xxx lines in GetMyBusinesses(), my results are not sorted any differently - they are always sorting it ascendingly. FYI, Name is a varchar(200) field in SQL 2008 on my Business table. private IQueryable<Business> GetMyBusinesses(MyDBContext CurrentContext) { var myBusinesses = from a in CurrentContext.A join f in CurrentContext.F on a.FID equals f.id join b in CurrentContext.Businesses on f.BID equals b.id where a.PersonID == 52 select b; var results = from r in myBusinesses orderby "Name" ascending select r; //var results = from r in results // orderby "Name" descending // select r; return results; } private PartialEntitiesList<Business> DoStuff() { var myBusinesses = GetMyBusinesses(); var myBusinessesCount = GetMyBusinesses().Count(); Results = new PartialEntitiesList<Business>(myBusinesses.Skip((PageNumber - 1)*PageSize).Take(PageSize).ToList()) {UnpartialTotalCount = myBusinessesCount}; return Results; } public class PartialEntitiesList<T> : List<T> { public PartialEntitiesList() { } public PartialEntitiesList(int capacity) : base(capacity) { } public PartialEntitiesList(IEnumerable<T> collection) : base(collection) { } public int UnpartialTotalCount { get; set; } }

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• Hibernate HQL m:n join problem

  - by smallufo

  I am very unfamiliar with SQL/HQL , and am currently stuck with this 'maybe' simple problem : I have two many-to-many Entities , with a relation table : Car , CarProblem , and Problem . One Car may have many Problems , One Problem may appear in many Cars, CarProblem is the association table with other properties . Now , I want to find Car(s) with specified Problem , how do I write such HQL ? All ids are Long type . I've tried a lot of join / inner-join combinations , but all in vain.. -- updated : Sorry , forget to mention : Car has many CarProblem Problem has many CarProblem Car and Problem are not directly connected in Java Object. -- update , java code below -- @Entity public class Car extends Model{ @OneToMany(mappedBy="car" , cascade=CascadeType.ALL) public Set<CarProblem> carProblems; } @Entity public class CarProblem extends Model{ @ManyToOne public Car car; @ManyToOne public Problem problem; ... other properties } @Entity public class Problem extends Model { other properties ... // not link to CarProblem , It seems not related to this problem // **This is a very stupid query , I want to get rid of it ...** public List<Car> findCars() { List<CarProblem> list = CarProblem.find("from CarProblem as cp where cp.problem.id = ? ", id).fetch(); Set<Car> result = new HashSet<Car>(); for(CarProblem cp : list) result.add(cp.car); return new ArrayList<Car>(result); } } The Model is from Play! framework , so these properties are all public .

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• mySQL select and group by values

  - by Foo

  I'd like to count and group rows by specific values. This seems fairly simple, but I can't seem to do it. I have a table set up similar to this: Table: Ratings id pID uID rating 1 1 2 7 2 1 7 7 3 1 5 4 4 1 1 1 id is the primary key, piD and uID are foreign-keys. Rating contains values between 1 and 10, and only between 1 and 10. I want to run some statistics and count the number of ratings with a certain value. In the example above, two have left a rating of 7. So I wrote the following query: SELECT COUNT(*) AS 'count' , 'rating' FROM 'ratings' WHERE pID= '1' GROUP BY `rating` ORDER BY `rating` Which yields the nice result as: count ratings 1 1 1 4 2 7 I'd like to get the mySQL query to include values between 1 and 10 as well. For example: Desired Result count ratings 1 1 0 2 0 3 1 4 0 5 0 6 2 7 0 8 0 9 0 10 Unfortunately, I'm relatively new to SQL and I've been reading through everything I could get my hands on for the past hour, but I can't get it to work. I've been leaning along the lines of a some type of JOIN. If anyone can point me in the right direction, it'd be appreciated. Thanks.

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• How to Implement search through Stored Procedure

  - by Manoj Wadhwani

  Can Any budy update thie sp for search , i think i have put search condition which is not rigth . If you have expertise in sql then update it , It's very urgent i have to upload it toady .. alter Procedure USP_SearchEmployee @EmpName varchar(100)=null, @DateFrom varchar(100)=null, @DateTo varchar(100)=null, @CourseName varchar(100)=null, @JobFunction varchar(100)=null, @Region varchar(100)=null, @Status varchar(100)=null AS BEGIN if (@EmpName!='' or @EmpName is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where EmpName like '%'+@EmpName+'%' END ELSE IF (@CourseName!='' or @CourseName is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where SpeCourse_ID like '%'+@CourseName+'%' END ELSE IF (@JobFunction!='' or @JobFunction is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where EmpJobFunction like '%'+@JobFunction+'%' END ELSE IF (@Region!='' or @Region is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where EmpRegion like '%'+@Region+'%' END ELSE IF (@Status!='' or @Status is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where Status like '%'+@Status+'%' END ELSE IF (@DateFrom!='' or @DateFrom is not null) BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS where convert(varchar,DueDate,101) =convert(varchar,@DateFrom,101) END Else BEGIN select EmpName,convert(varchar,DueDate,101) as DueDate,SpeCourse_ID as CourseName, EmpJobFunction as JOBFunction,EmpRegion as Region,Status from Training_TRNS END END

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• JDBC Lock a row using SELECT FOR UPDATE, doesn't work

  - by Rachid

  I am having issues with MySQL's SELECT .. FOR UPDATE, here is the query I am trying to run: SELECT * FROM tableName WHERE HostName='UnknownHost' ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE After this, the concerned thread will do an UPDATE and change the HostName, which is then it should unlock the row. I am running a multi-threaded java application, so 3 threads are running this SQL statement, but when thread 1 runs this, it doesn't lock its results from thread 2 & 3. Therefore threads 2 & 3 are getting the same results and they could update the same row. Also each thread is on its own mysql connection. I'm using Innodb, with transaction-isolation = READ-COMMITTED, and the Autocommit is off before executing the select for update may I miss something? OR perhaps there is a better solution? Thanks a lot. Code : public BasicJDBCDemo() { Le_Thread newThread1=new Le_Thread(); Le_Thread newThread2=new Le_Thread(); newThread1.start(); newThread2.start(); } Thread : class Le_Thread extends Thread { public void run() { tring name = Thread.currentThread().getName(); System.out.println( name+": Debut."); long oid=Util.doSelectLockTest(name); Util.doUpdateTest(oid,name); } } Select : public static long doSelectLockTest(String threadName) { System.out.println("[OUTPUT FROM SELECT Lock ]...threadName="+threadName); PreparedStatement pst = null; ResultSet rs=null; Connection conn=null; long oid=0; try { String query = "SELECT * FROM table WHERE Host=? ORDER BY Timestamp asc limit 1 FOR UPDATE"; conn=getNewConnection(); pst = conn.prepareStatement(query); pst.setString(1, DbProperties.UnknownHost); System.out.println("pst="+threadName+"__"+pst); rs = pst.executeQuery(); if (rs.first()) { String s = rs.getString("HostName"); oid = rs.getLong("OID"); System.out.println("oid_oldest/host/threadName=="+oid+"/"+s+"/"+threadName); } } catch (SQLException ex) { ex.printStackTrace(); } finally { DBUtil.close(pst); DBUtil.close(rs); DBUtil.close(conn); } return oid; } Please help.... : Result : Thread-1: Debut. Thread-2: Debut. [OUTPUT FROM SELECT Lock ]...threadName=Thread-1 New connection.. [OUTPUT FROM SELECT Lock ]...threadName=Thread-2 New connection.. pst=Thread-2: SELECT * FROM b2biCheckPoint WHERE HostName='UnknownHost' ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE pst=Thread-1: SELECT * FROM b2biCheckPoint WHERE HostName='UnknownHost' ORDER BY UpdateTimestamp asc limit 1 FOR UPDATE oid_oldest/host/threadName==1/UnknownHost/Thread-2 oid_oldest/host/threadName==1/UnknownHost/Thread-1 [Performing UPDATE] ... oid = 1, thread=Thread-2 New connection.. [Performing UPDATE] ... oid = 1, thread=Thread-1 pst_threadname=Thread-2: UPDATE b2bicheckpoint SET HostName='1_host_Thread-2',UpdateTimestamp=1294940161838 where OID = 1 New connection.. pst_threadname=Thread-1: UPDATE b2bicheckpoint SET HostName='1_host_Thread-1',UpdateTimestamp=1294940161853 where OID = 1

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• Populate JOIN into a list in one database query

  - by axio

  I am trying to get the records from the 'many' table of a one-to-many relationship and add them as a list to the relevant record from the 'one' table. I am also trying to do this in a single database request. Code derived from http://stackoverflow.com/questions/1580199/linq-to-sql-populate-join-result-into-a-list almost achieves the intended result, but makes one database request per entry in the 'one' table which is unacceptable. That failing code is here: var res = from variable in _dc.GetTable<VARIABLE>() select new { x = variable, y = variable.VARIABLE_VALUEs }; However if I do a similar query but loop through all the results, then only a single database request is made. This code achieves all goals: var res = from variable in _dc.GetTable<VARIABLE>() select variable; List<GDO.Variable> output = new List<GDO.Variable>(); foreach (var v2 in res) { List<GDO.VariableValue> values = new List<GDO.VariableValue>(); foreach (var vv in v2.VARIABLE_VALUEs) { values.Add(VariableValue.EntityToGDO(vv)); } output.Add(EntityToGDO(v2)); output[output.Count - 1].VariableValues = values; } However the latter code is ugly as hell, and it really feels like something that should be do-able in a single linq query. So, how can this be done in a single linq query that makes only a single database query? In both cases the table is set to preload using the following code: _dc = _db.CreateLinqDataContext(); var loadOptions = new DataLoadOptions(); loadOptions.LoadWith<VARIABLE>(v => v.VARIABLE_VALUEs); _dc.LoadOptions = loadOptions; I am using .NET 3.5, and the database back-end was generated using SqlMetal.

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• transaction handling in dataset based insert/update in c#

  - by user3703611

  I am trying to insert bulk records in a sql server database table using dataset. But i am unable to do transaction handling. Please help me to apply transaction handling in below code. I am using adapter.UpdateCommand.Transaction = trans; but this line give me an error of Object reference not set to an instance of an object. Code: string ConnectionString = "server=localhost\\sqlexpress;database=WindowsApp;Integrated Security=SSPI;"; SqlConnection conn = new SqlConnection(ConnectionString); conn.Open(); SqlTransaction trans = conn.BeginTransaction(IsolationLevel.Serializable); SqlDataAdapter adapter = new SqlDataAdapter("SELECT * FROM Test ORDER BY Id", conn); SqlCommandBuilder builder = new SqlCommandBuilder(adapter); adapter.UpdateCommand.Transaction = trans; // Create a dataset object DataSet ds = new DataSet("TestSet"); adapter.Fill(ds, "Test"); // Create a data table object and add a new row DataTable TestTable = ds.Tables["Test"]; for (int i=1;i<=50;i++) { DataRow row = TestTable.NewRow(); row["Id"] = i; TestTable .Rows.Add(row); } // Update data adapter adapter.Update(ds, "Test"); trans.Commit(); conn.Close();

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• referencing part of the composite primary key

  - by Zavael

  I have problems with setting the reference on database table. I have following structure: CREATE TABLE club( id INTEGER NOT NULL, name_short VARCHAR(30), name_full VARCHAR(70) NOT NULL ); CREATE UNIQUE INDEX club_uix ON club(id); ALTER TABLE club ADD CONSTRAINT club_pk PRIMARY KEY (id); CREATE TABLE team( id INTEGER NOT NULL, club_id INTEGER NOT NULL, team_name VARCHAR(30) ); CREATE UNIQUE INDEX team_uix ON team(id, club_id); ALTER TABLE team ADD CONSTRAINT team_pk PRIMARY KEY (id, club_id); ALTER TABLE team ADD FOREIGN KEY (club_id) REFERENCES club(id); CREATE TABLE person( id INTEGER NOT NULL, first_name VARCHAR(20), last_name VARCHAR(20) NOT NULL ); CREATE UNIQUE INDEX person_uix ON person(id); ALTER TABLE person ADD PRIMARY KEY (id); CREATE TABLE contract( person_id INTEGER NOT NULL, club_id INTEGER NOT NULL, wage INTEGER ); CREATE UNIQUE INDEX contract_uix on contract(person_id); ALTER TABLE contract ADD CONSTRAINT contract_pk PRIMARY KEY (person_id); ALTER TABLE contract ADD FOREIGN KEY (club_id) REFERENCES club(id); ALTER TABLE contract ADD FOREIGN KEY (person_id) REFERENCES person(id); CREATE TABLE player( person_id INTEGER NOT NULL, team_id INTEGER, height SMALLINT, weight SMALLINT ); CREATE UNIQUE INDEX player_uix on player(person_id); ALTER TABLE player ADD CONSTRAINT player_pk PRIMARY KEY (person_id); ALTER TABLE player ADD FOREIGN KEY (person_id) REFERENCES person(id); -- ALTER TABLE player ADD FOREIGN KEY (team_id) REFERENCES team(id); --this is not working It gives me this error: Error code -5529, SQL state 42529: a UNIQUE constraint does not exist on referenced columns: TEAM in statement [ALTER TABLE player ADD FOREIGN KEY (team_id) REFERENCES team(id)] As you can see, team table has composite primary key (club_id + id), the person references club through contract. Person has some common attributes for player and other staff types. One club can have multiple teams. Employed person has to have a contract with a club. Player (is the specification of person) - if emplyed - can be assigned to one of the club's teams. Is there better way to design my structure? I thought about excluding the club_id from team's primary key, but I would like to know if this is the only way. Thanks. UPDATE 1 I would like to have the id as team identification only within the club, so multiple teams can have equal id as long as they belong to different clubs. Is it possible? UPDATE 2 updated the naming convention as adviced by philip Some business rules to better understand the structure: One club can have 1..n teams (Main squad, Reserve squad, Youth squad or Team A, Team B... only team can play match, not club) One team belongs to one club only A player is type of person (other types (staff) are scouts, coaches etc so they do not need to belong to specific team, just to the club, if employed) Person can have 0..1 contract with 1 club (that means he is employed or unemployed) Player (if employed) belongs to one team of the club Now thinking about it - moving team_id from player to contract would solve my problem, and it could hold the condition "Player (if employed) belongs to one team of the club", but it would be redundant for other staff types. What do you think?

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• Why are my bound parameters all identical (using Linq)?

  - by Scott Stafford

  When I run this snippet of code: string[] words = new string[] { "foo", "bar" }; var results = from row in Assets select row; foreach (string word in words) { results = results.Where(row => row.Name.Contains(word)); } I get this SQL: -- Region Parameters DECLARE @p0 VarChar(5) = '%bar%' DECLARE @p1 VarChar(5) = '%bar%' -- EndRegion SELECT ... FROM [Assets] AS [t0] WHERE ([t0].[Name] LIKE @p0) AND ([t0].[Name] LIKE @p1) Note that @p0 and @p1 are both bar, when I wanted them to be foo and bar. I guess Linq is somehow binding a reference to the variable word rather than a reference to the string currently referenced by word? What is the best way to avoid this problem? (Also, if you have any suggestions for a better title for this question, please put it in the comments.) Note that I tried this with regular Linq also, with the same results (you can paste this right into Linqpad): string[] words = new string[] { "f", "a" }; string[] dictionary = new string[] { "foo", "bar", "jack", "splat" }; var results = from row in dictionary select row; foreach (string word in words) { results = results.Where(row => row.Contains(word)); } results.Dump(); Dumps: bar jack splat

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• MS-Access auto enter information based on date

  - by Desert Spider

  I have a query that calculates an employees anniversary date. I would like that query to generate an entry event for my Table based on the current date. Basically automatically generate an anniversary vacation accrual when their anniversary date comes. Here is an example of my table. Table name "SchedulingLog" LogID "PrimaryKey AutoNbr" UserID "Employee specific" LogDate EventDate Category "ex Vacation, Anniversary..." CatDetail "ex. Vacation Day Used, Anniversary..." Value "ex. -1, 1..." My query Query Name "qry_YOS" UserID "Employee Specific" DOH "Employee hire date" YearsOfService "calculated Field" Annual "calculated Field" Schedule "Employee Specific" Annual Vac Days "calculated field" Anniversary "calculated Field" Query associated SQL INSERT INTO schedulinglog (userid, [value], eventdate, logdate, category, catdetail) SELECT roster.userid, [annual] * [schedule] AS [Value], Month([wm doh]) & "/" & Day([wm doh]) & "/" & Year(DATE()) AS EventDate, DATE() AS LogDate, category.[category name] AS Category, catdetail.catdetail FROM roster, tblaccrual, category INNER JOIN catdetail ON category.categoryid = catdetail.categoryid WHERE (( ( [tblaccrual] ! [years] ) < Round(( DATE() - [wm doh] ) / 365, 2) )) GROUP BY roster.userid, roster.[wm doh], Round(( DATE() - [wm doh] ) / 365, 2), roster.schedule, Month([wm doh]) & "/" & Day([wm doh]) & "/" & Year(DATE()), DATE(), category.[category name], catdetail.catdetail HAVING ( ( ( category.[category name] ) LIKE "vacation*" ) AND ( ( catdetail.catdetail ) LIKE "anniversary*" ) ); I know it is possible I just dont know where to begin.

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• Postgresql Output column from another table

  - by muffin

  i'm using Postgresql, my question is specifically about querying from a table that's in another table and i'm really having trouble with this one. In fact, i'm absolutely mentally blocked. I'll try to define the relations of the tables as much as I can. I have a table entry which is like this: Each of the entries has a group_id; when they are 'advanced' to the next stage, the old entries are marked is_active = false, and a new assignment is done, so C & D are advanced stages of A & B. I have another table (which acts as a record keeper) , in which the storage_log_id refers to, this is the storage_log table : But then I have another table, to really find out where the entries are actually stored - storage table : To define my problem properly. Each entry has a storage_log_id (but some doesn't have yet), and a storage_log has a storage_id to refer to the actual table and find the storage label. The sql query i'm trying to do should output this one: Where The actual storage label is shown instead of the log id. This is so far what i've done: select e.id, e.group_id, e.name, e.stage, s.label from operational.entry e, operational.storage_log sl, operational.storage s where e.storage_log_id = sl.id and sl.storage_id = s.id But this just returns 3 rows, showing only the ones that have the seed_storage_log_id set; I should be able to see even those without logs, and especially the active ones. adding e.is_active = true to the condition makes the results empty. So, yeah i'm stuck. Need help, Thanks guys!

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• when to use Hibernate vs. Simple ResultSets for small application

  - by luke

  I just started working on upgrading a small component in a distributed java application. The main application is a rather complicated applet/servlet combo running on JBoss and it extensively uses Hibernate for its DataAccess. The component i am working on however is very a very straightforward data importing service. Basically the workflow is Listen for a network event Parse the data packet, extract a set of identifiers Map the identifier set to a primary key in our database Parse the rest of the packet and insert items in a related table using the foreign key found in step 3 Repeat in the previous version of this component it used a hibernate based DAL, that is no longer usable for a variety of reasons (in particular it is EOL), so I am in charge of replacing the Data Access layer for this component. So on the one hand I think i should use Hibernate because that's what the rest of the application does, but on the other i think i should just use regular java.sql.* classes because my requirements are really straightforward and aren't expected to change any time soon. So my question is (and i understand it is subjective) at what point do you think that the added complexity of using an ORM tool (in terms of configuration, dependencies...) is worth it? UPDATE due to the way the DataAccesLayer for the main application was written (weird dependencies) i cannot easily use it, i would have to implement it myself.

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