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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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• SQL query error while trying to put a file in the database

  - by DaGhostman Dimitrov

  Hey Guys I have a big problem that I have no Idea why.. I have few forms that upload files to the database, all of them work fine except one.. I use the same query in all(simple insert). I think that it has something to do with the files i am trying to upload but I am not sure. Here is the code: if ($_POST['action'] == 'hndlDocs') { $ref = $_POST['reference']; // Numeric value of $doc = file_get_contents($_FILES['doc']['tmp_name']); $link = mysqli_connect('localhost','XXXXX','XXXXX','documents'); mysqli_query($link,"SET autocommit = 0"); $query = "INSERT INTO documents ({$ref}, '{$doc}', '{$_FILES['doc']['type']}') ;"; mysqli_query($link,$query); if (mysqli_error($link)) { var_dump(mysqli_error($link)); mysqli_rollback($link); } else { print("<script> window.history.back(); </script>"); mysqli_commit($link); } } The database has only these fields: DATABASE documents ( reference INT(5) NOT NULL, //it is unsigned zerofill doc LONGBLOB NOT NULL, //this should contain the binary data mime_type TEXT NOT NULL // the mime type of the file php allows only application/pdf and image/jpeg ); And the error I get is : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '00001, '????' at line 1 I will appreciate every help. Cheers!

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• How to write my own global lock / unlock functions for PostgreSQL

  - by rafalmag

  I have postgresql (in perlu) function getTravelTime(integer, timestamp), which tries to select data for specified ID and timestamp. If there are no data or if data is old, it downloads them from external server (downloading time ~300ms). Multiple process use this database and this function. There is an error when two process do not find data and download them and try to do an insert to travel_time table (id and timestamp pair have to be unique). I thought about locks. Locking whole table would block all processes and allow only one to proceed. I need to lock only on id and timestamp. pg_advisory_lock seems to lock only in "current session". But my processes uses their own sessions. I tried to write my own lock/unlock functions. Am I doing it right? I use active waiting, how can I omit this? Maybe there is a way to use pg_advisory_lock() as global lock? My code: CREATE TABLE travel_time_locks ( id_key integer NOT NULL, time_key timestamp without time zone NOT NULL, UNIQUE (id_key, time_key) ); ------------ -- Function: mylock(integer, timestamp) DROP FUNCTION IF EXISTS mylock(integer, timestamp) CASCADE; -- Usage: SELECT mylock(1, '2010-03-28T19:45'); -- function tries to do a global lock similar to pg_advisory_lock(key, key) CREATE OR REPLACE FUNCTION mylock(id_input integer, time_input timestamp) RETURNS void AS $BODY$ DECLARE rows int; BEGIN LOOP BEGIN -- active waiting here !!!! :( INSERT INTO travel_time_locks (id_key, time_key) VALUES (id_input, time_input); EXCEPTION WHEN unique_violation THEN CONTINUE; END; EXIT; END LOOP; END; $BODY$ LANGUAGE 'plpgsql' VOLATILE COST 1; ------------ -- Function: myunlock(integer, timestamp) DROP FUNCTION IF EXISTS myunlock(integer, timestamp) CASCADE; -- Usage: SELECT myunlock(1, '2010-03-28T19:45'); -- function tries to do a global unlock similar to pg_advisory_unlock(key, key) CREATE OR REPLACE FUNCTION myunlock(id_input integer, time_input timestamp) RETURNS integer AS $BODY$ DECLARE BEGIN DELETE FROM ONLY travel_time_locks WHERE id_key=id_input AND time_key=time_input; RETURN 1; END; $BODY$ LANGUAGE 'plpgsql' VOLATILE COST 1;

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• MySQL: SELECT highest column value when WHERE finds similar entries

  - by Ike

  My question is comparable to this one, but not quite the same. I have a database with a huge amount of books, with different editions of some of the same book titles. I'm looking for an SQL statement giving me the highest edition number of each of the titles I'm selecting with a WHERE clause (to find specific book series). Here's what the table looks like: |id|title |edition|year| |--|-------------------------|-------|----| |01|Serie One Title One |1 |2007| |02|Serie One Title One |2 |2008| |03|Serie One Title One |3 |2009| |04|Serie One Title Two |1 |2001| |05|Serie One Title Three |1 |2008| |06|Serie One Title Three |2 |2009| |07|Serie One Title Three |3 |2010| |08|Serie One Title Three |4 |2011| |--|-------------------------|-------|----| The result I'm looking for is this: |id|title |edition|year| |--|-------------------------|-------|----| |03|Serie One Title One |3 |2009| |04|Serie One Title Two |1 |2001| |08|Serie One Title Three |4 |2011| |--|-------------------------|-------|----| The closest I got was using this statement: select id, title, max(edition), max(year) from books where title like "serie one%" group by name; but it returns the highest edition and year and includes the first id it finds: |--|-----------------------|-------|----| |01|Serie One Title One |3 |2009| |04|Serie One Title Two |1 |2001| |05|Serie One Title Three |4 |2011| |--|-----------------------|-------|----| This fancy join also comes close, but doesn't give the right result: select b.id, b.title, b.edition, b.year from books b inner join (select name, max(edition) as maxedition from books group by title) g on b.edition = g.maxedition where b.title like "serie one%" group by title; Using this I'm getting unique titles, but mostly old editions.

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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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• How do I make software that preserves database integrity and correctness? Please help, confused.

  - by user287745

  i have made an application project in vs 08 c#, sql server from vs 08. the database has like 20 tables and many fields in each have made an interface for adding deleting editting and retrieving data according to predefined needs of the users. now i have to 1) make to project in to a software which i can deliver to professor. that is he can just double click the icon and the software simply starts. no vs 08 needed to start the debugging 2) the database will be on one powerful computer (dual core latest everything win xp) and the user will access it from another computer connected using LAN i am able to change the connection string to the shared database using vs 08/ debugger whenever the server changes but how am i supposed to do that when its a software? 3)there will by many clients am i supposed to give the same software to every one, so they all can connect to the database, how will the integrity and correctness of the database be maintained? i mean the db.mdf file will be in a folder which will be shared with read and write access. so its not necessary that only one user will write at a time. so is there any coding for this or? please help me out here i am stuck do not know what to do i have no practical experience, would appreciate all the help thank you

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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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• Git: How to revert everything exactly to the state of a prior commit?

  - by williamjones

  If there have been commits and many changes since an earlier commit, is there a simple way to revert everything to the exact state of that earlier commit? If so, is it possible to easily switch back to the current state if I should so desire as well?

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• T-SQL: how to sort table rows based on 2 columns

  - by Criss Nautilus

  I'm quite stuck with this problem for sometime now.. How do I sort column A depending on the contents of Column B? I have this sample: ID count columnA ColumnB 12 1 A B 13 2 C D 14 3 B C I want to sort it like this: ID count ColumnA ColumnB 12 1 A B 14 3 B C 13 2 C D so I need to sort the rows if the previous row of ColumnB = the next row of ColumnA I'm thinking a loop? but can't quite imagine how it will work... I was thinking it will go like this (maybe) SELECT a.ID, a.ColumnA, a.ColumnB FROM TableA WITH a (NOLOCK) LEFT JOIN TableA b WITH (NOLOCK) ON a.ID = b.ID and a.counts = b.counts Where a.columnB = b.ColumnA the above code isn't working though and I was thinking more on the lines of... DECLARE @counts int = 1 DECLARE @done int = 0 --WHILE @done = 0 BEGIN SELECT a.ID, a.ColumnA, a.ColumnB FROM TableA WITH a (NOLOCK) LEFT JOIN TableA b WITH (NOLOCK) ON a.ID = b.ID and a.counts = @counts Where a.columnB = b.ColumnA set @count = @count +1 END If this was a C code, would be easier for me but t-sql's syntax is making it a bit harder for a noobie like me.

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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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• 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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• Is the source code of the demo at WWDC 09, Session 304 available?

  - by mystify

  At WWDC 09 in Session 304 "Game Development for iPhone, Part 1 (Graphics, Audio)", about 6 minutes after start of the Session, they showed off a small but nice OpenGL ES game demo and repeating over and over again how easy it is to implement. Is that source code of the demo available somewhere for download?

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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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• Using a variable derived from a drop-down list as the column name in a select statement ... Access DB

  - by user1459698

  I'm working with the world's worst DB that was already here so don't blame me for that. So, here's what I have so far ... module = txtModule.value presstype = txtPressType.value SQL_query = "SELECT * FROM tbl_spareparts WHERE '"& module &"' <> '""' AND '"& module &"' = '"& presstype &"' AND Manufacturer = '"& txtsrch.value &"' ORDER BY SAP_Part_No" Set rsData = conn.Execute(SQL_query) This brings up the following SQL statement: SELECT * FROM tbl_spareparts WHERE 'Banyan_Module' <> '"' AND 'Banyan_Module' = 'PB' AND Manufacturer = 'Tester' ORDER BY SAP_Part_No Is there any way I can use the module variable as a column name - obviously the ''s around the column name are causing an error. This is really bothering me. BTW, I'm writing this in VBScript inside a .HTA application page as it has to run locally on tech PCs. Thanks. R.

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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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• IN SQL operator in R-Shiny

  - by Piyush

  I am taking multiple selection for component as per below code. selectInput("cmpnt", "Choose Component:", choices = as.character(levels(Material_Data()$CMPNT_NM)),multiple = TRUE) But I am trying to write a sql statement as given below, then its not working. Neither it is throwing any error message. When I was selecting one option at a time (without mutiple = TRUE) then it was working (since I was using "=" operator). But after using "multiple=TRUE" I need to use IN operator, which is not working. Input_Data2 <- fn$sqldf( paste0( "select * from Input_Data1 where MTRL_NBR = '$mtrl1' and CMPNT_NM in ('$cmpnt1')") ) Thanks in advance for any help on this. Thanks jdharrison! Pleasefind the detailed code: # server.R library(RODBC) library(shiny) library(sqldf) Input_Data <- readRDS("InputSource.rds") Mtrl <- factor(Input_Data$MTRL_NBR) Mtrl_List <- levels(Mtrl) shinyServer(function(input, output) { # First UI input (Service column) filter clientData output$Choose_Material <- renderUI({ if (is.null(clientData())) return("No client selected") selectInput("mtrl", "Choose Material:", choices = as.character(levels(clientData()$MTRL_NBR)), selected = input$mtrl ) }) # Second UI input (Rounds column) filter service-filtered clientData output$Choose_Component <- renderUI({ if(is.null(input$mtrl)) return() if (is.null(Material_Data())) return("No service selected") selectInput("cmpnt", "Choose Component:", choices = as.character(levels(Material_Data()$CMPNT_NM)),multiple = TRUE) }) # First data load (client data) clientData <- reactive({ # get(input$Input_Data) return(Input_Data) }) # Second data load (filter by service column) Material_Data <- reactive({ dat <- clientData() if (is.null(dat)) return(NULL) if (!is.null(input$mtrl)) # ! dat <- dat[dat$MTRL_NBR %in% input$mtrl,] dat <- droplevels(dat) return(dat) }) output$Choose_Columns <- renderUI({ if(is.null(input$mtrl)) return() if(is.null(input$cmpnt)) return() colnames <- names(Input_Data) checkboxGroupInput("columns", "Choose Columns To Display The Data:", choices = colnames, selected = colnames) }) output$text <- renderText({ print(input$cmpnt) }) output$data_table <- renderTable({ if(is.null(input$mtrl)) return() if (is.null(input$columns) || !(input$columns %in% names(Input_Data))) return() Input_Data1 <- Input_Data[, input$columns, drop = FALSE] cmpnt1 <- input$cmpnt mtrl1 <- input$mtrl Input_Data2 <- fn$sqldf( paste0( "select * from Input_Data1 where MTRL_NBR = '$mtrl1' and CMPNT_NM in ('$cmpnt1')") ) head(Input_Data2, 10) }) })

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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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• 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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• 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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• What does "Select Distinct Null As xxxxx" mean?

  - by Soylent Green

  Background: I am mapping Sybase stored procedure return values to java objects using Spring. For example I map a Sybase datatype of varchar as a String type in Java, and a Sybase datatype of int as an int type in Java, etc. I have come across the following code in one of the stored procedures: SELECT DISTINCT A.Col1 AS val1, A.Col2 AS val2, NULL AS someVal, A.col3 AS val3, ... A.col9 AS val9 FROM #SomeTable A ORDER BY Col2, Col3 I have 2 related questions: What does Null mean in this scenario? I am confused as to what is happening here. I am able to determine the data type of Col1, Col2, etc. of course by looking at the table definition of Table A defined earlier in the stored procedure. Thus I know what datatype I can define in my Java object for val1, val2, etc.. But what about "someVal"? What datatype mapping am I supposed to perform for this Null value? I am fairly inexperienced in SQL. Perhaps the answer is much simpler than I realize.

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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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• Django/jquery: Address forms - dyamically adding state drop down list if country is United States?

  - by User

  I have a django html form for address information. There is standard street, city, state/province, postal code, country fields. The country field is a drop down list. How can I make the state/province field a drop down list if the selected country is united states and a free form text box if the country is anything else? I'd prefer not to have to do a round trip to the server so probably through jquery?

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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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