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• Yahoo Query Language Problem

  - by Damiano

  Hello everybody! Today, I've started with Yahoo Query Language. I would use it to retrive stocks details, so I'm talking about Yahoo Finance. I think there is a bug on this language. This is my query: select * from yahoo.finance.quoteslist where symbol='@^GSPC' I ALWAYS get 51 results! it's impossible, take a look at: http://it.finance.yahoo.com/q/cp?s=^GSPC There are 500 results! I also tried some paging parameters. select * from yahoo.finance.quoteslist(50,30) where symbol='@^GSPC' (to get from 50 to 80) select * from yahoo.finance.quoteslist(100) where symbol='@^GSPC' (to get the first 100 results) select * from yahoo.finance.quoteslist where symbol='@^GSPC' limit 30 offset 50 but ALWAYS the last stock is: <quote symbol="BBY"> <Symbol>BBY</Symbol> <LastTradePriceOnly>41.03</LastTradePriceOnly> <LastTradeDate>5/7/2010</LastTradeDate> <LastTradeTime>4:00pm</LastTradeTime> <Change>-0.48</Change> <Open>41.35</Open> <DaysHigh>42.35</DaysHigh> <DaysLow>39.60</DaysLow> <Volume>14129531</Volume> </quote> Why do I have this kind of problem? Thank you so much for your support! (P.S. I've tested it on Yahoo YQL console)

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• How to update non-scalar entity properties in EF 4.0?

  - by Mike

  At first I was using this as an extension method to update my detached entities... Public Sub AttachUpdated(ByVal obj As ObjectContext, ByVal objectDetached As EntityObject) If objectDetached.EntityState = EntityState.Detached Then Dim original As Object = Nothing If obj.TryGetObjectByKey(objectDetached.EntityKey, original) Then obj.ApplyCurrentValues(objectDetached.EntityKey.EntitySetName, objectDetached) Else Throw New ObjectNotFoundException() End If End If End Sub Everything has been working great until I had to update non-scalar properties. Correct me if I am wrong but that is because "ApplyCurrentValues" only supports scalars. To get around this I was just saving the FK_ID field instead of the entity object relation. Now I am faced with a many to many relationship so its not that simple. I would like to do something like this... Dim Resource = RelatedResource.GetByID(item.Value) Condition.RelatedResources.Add(Resource) But when I call SaveChanges the added Resources aren't saved. I started to play around with self-tracking entities (not sure if they will help solve my prob) but it seems they cannot be serialized to ViewState and this is a requirement for me. I guess one solution would be to add the xRef table as an entity and add the fks myself but I would rather it just work how I expect it too. I am open to any suggestions on how to either save my many to many relationships or serialize self-tracking entities (if self-trackingwould even solve my problem). Thanks!

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• Select all points in a matrix within 30m of another point

  - by pinnacler

  So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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• What is the best method for updating all changed data in EF 4?

  - by Soul_Master

  I try to create some method that can update any changed data from changed Data object (this object is generated by ASP.NET MVC) to old Data object (this object is retrieved from current data in DBMS) like the following code. public static bool UpdateSomeData(SomeEntities context, SomeModelType changedData) { var oldData = GetSomeModelTypeById(context, changedData.ID); UpdateModel(oldData, changedData); return context.SaveChanges() > 0; } I try to create method for saving any changed data without affects other unchanged data like the following source code. public static void UpdateModel<TModel>(TModel oldData, TModel changedData) { foreach (var pi in typeof(TModel).GetProperties() .Where ( // Ignore Change ID property for security reason x => x.Name.ToUpper() != "ID" && x.CanRead && x.CanWrite && ( // It must be primitive type or Guid x.PropertyType.FullName.StartsWith("System") && !x.PropertyType.FullName.StartsWith("System.Collection") && !x.PropertyType.FullName.StartsWith("System.Data.Entity.DynamicProxies") ) ) { var oldValue = pi.GetValue(oldData, null); var newValue = pi.GetValue(changedData, null); if (!oldValue.Equals(newValue)) { pi.SetValue(oldData, newValue, null); } } } I am not sure about the above method because it is so ugly method for updating data. From recent bug, it realizes me that if you update some property like Navigation Properties (related data from other table), it will remove current record from database. I don't understand why it happened. But it is very dangerous for me. So, do you have any idea for this question to ensure me about updating data from ASP.NET MVC? Thanks,

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• What is a good approach to preloading data?

  - by Bob Horn

  Are there best practices out there for loading data into a database, to be used with a new installation of an application? For example, for application foo to run, it needs some basic data before it can even be started. I've used a couple options in the past: TSQL for every row that needs to be preloaded: IF NOT EXISTS (SELECT * FROM Master.Site WHERE Name = @SiteName) INSERT INTO [Master].[Site] ([EnterpriseID], [Name], [LastModifiedTime], [LastModifiedUser]) VALUES (@EnterpriseId, @SiteName, GETDATE(), @LastModifiedUser) Another option is a spreadsheet. Each tab represents a table, and data is entered into the spreadsheet as we realize we need it. Then, a program can read this spreadsheet and populate the DB. There are complicating factors, including the relationships between tables. So, it's not as simple as loading tables by themselves. For example, if we create Security.Member rows, then we want to add those members to Security.Role, we need a way of maintaining that relationship. Another factor is that not all databases will be missing this data. Some locations will already have most of the data, and others (that may be new locations around the world), will start from scratch. Any ideas are appreciated.

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• Guid Primary /Foreign Key dilemma SQL Server

  - by Xience

  Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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• [Qt] How to get rid of OCI.dll dependency when compiling static

  - by STL

  Hi, My application accesses an Oracle database through Qt's QSqlDatabase class. I'm compiling Qt as static for the release build, but I can't seem to be able to get rid of OCI.dll dependency. I'm trying to link against oci.lib (as available in Oracle's Instant Client with SDK). Here's my configure line : configure -qt-libjpeg -qt-zlib -qt-libpng -nomake examples -nomake demos -no-exceptions -no-stl -no-rtti -no-qt3support -no-scripttools -no-openssl -no-opengl -no-phonon -no-style-motif -no-style-cde -no-style-cleanlooks -no-style-plastique -static -release -opensource -plugin-sql-oci -plugin-sql-sqlite -platform win32-msvc2005 I link against oci.h and oci.lib in the SDK's folder by using : set INCLUDE=C:\oracle\instantclient\sdk\include;%INCLUDE% set LIB=C:\oracle\instantclient\sdk\lib\msvc;%LIB% Then, once Qt is compiled, I use the following lines in my *.pro file : QT += sql CONFIG += static LIBS += C:\oracle\instantclient\sdk\lib\msvc\oci.lib QTPLUGIN += qsqloci Then, in my main.cpp, I add the following commands to statically compile OCI plugin in the application : #include <QtPlugin> Q_IMPORT_PLUGIN(qsqloci) After compiling the project, I test it on my workstation and it works (as I have Oracle Instant Client installed). When I try on another workstation, I always get the message: This application has failed to start because OCI.dll was not found. Re-installing this application may fix this problem. I don't understand why I still need OCI.dll, as my statically linked application is supposed to link to oci.lib instead. Is there any Qt people here that might have a solution for me ? Thanks a lot ! STL

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• ob_start() is partially capturing data

  - by AAA

  I am using the following code: PHP: // Generate Guid function NewGuid() { $s = strtoupper(uniqid(rand(),true)); $guidText = substr($s,0,8) . '-' . substr($s,8,4) . '-' . substr($s,12,4). '-' . substr($s,16,4). '-' . substr($s,20); return $guidText; } // End Generate Guid $Guid = NewGuid(); $alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'; function base_encode($num, $alphabet) { $base_count = strlen($alphabet); $encoded = ''; while ($num >= $base_count) { $div = $num/$base_count; $mod = ($num-($base_count*intval($div))); $encoded = $alphabet[$mod] . $encoded; $num = intval($div); } if ($num) $encoded = $alphabet[$num] . $encoded; return $encoded; } function base_decode($num, $alphabet) { $decoded = 0; $multi = 1; while (strlen($num) > 0) { $digit = $num[strlen($num)-1]; $decoded += $multi * strpos($alphabet, $digit); $multi = $multi * strlen($alphabet); $num = substr($num, 0, -1); } return $decoded; } ob_start(); echo base_encode($Guid, $alphabet); //should output: bUKpk $theid = ob_get_contents(); ob_get_clean(); The problem: When i echo $theid, it shows the complete entry, but as it is being inserted into the database, only the first entry in the sequence gets inserted, for example for the entry buKPK, only 'b' is being inserted not the rest.

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• MS Access 2003 - Failure to create MDE file: error VBA is corrupt?

  - by Justin

  Ok so this is a brand new snag I have run into. I am trying to launch a new MDE from my source MDB file, and it is locking up Access. So in my mdb, I am first compacting and repairing, and then selecting create a new mde (just as I have done many times before). It looks like it is starting the process, but never gets to where it compacts when it is done, and access is not responding. So after I force close the app, I look in the folder where I am trying to create the MDE to and I see there is a new access db1 file there. If I try to open that it gives me an error that says file not found, and then it says the Visual Basic for Applications is corrupt. The thing is, I just made a very simple adjustment to the code since last launching an mde, and after this I double and triple checked it...its not that because its just a simple open this form and close this one addition. I did however have my source mdb file on a disc that I copied to my laptop, and then tried to re link the tables to the network drive (had them linked to other tables on my local drive so that I could develop offline)?? PLEASE HELP!!!

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• PHP code displayed in browser

  - by Drake

  so, I'm working on a databases project, and i'm trying to code incrementally. the problem is, when i go to test the php in browser, it displays the php code after my use of "-". the html printing is displayed properly, which is AFTER the point where the - is. here is the php: <?php function getGraphicNovel(){ include_once("./connect.php"); $db_connection = new mysqli($SERVER, $USERNAME, $PASSWORD, $DATABASE); if (mysqli_connect_errno()) { echo("Can't connect to MySQL Server. Error code: " . mysqli_connect_error()); return null; } $stmt = $db_connection->stmt_init(); $returnValue = "invalid"; if($stmt.prepare("select series from graphic_novel_main natural join graphic_novel_misc")) { $stmt->execute(); $stmt->bind_result($series); while ($stmt->fetch()) { echo "<tr><td>" . $series . "</td></tr>"; } $stmt->close(); } $db_connection->close(); } getGraphicNovel(); ?> here is a link to the page. hopefully it works for people outside the school's network. http://plato.cs.virginia.edu/~paw5k/cainedb/viewall.html if anyone knows why this is happening, your input would be great!

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• How do I get save (no exclamation point) semantics in an ActiveRecord transaction?

  - by James A. Rosen

  I have two models: Person and Address which I'd like to create in a transaction. That is, I want to try to create the Person and, if that succeeds, create the related Address. I would like to use save semantics (return true or false) rather than save! semantics (raise an ActiveRecord::StatementInvalid or not). This doesn't work because the user.save doesn't trigger a rollback on the transaction: class Person def save_with_address(address_options = {}) transaction do self.save address = Address.build(address_options) address.person = self address.save end end end (Changing the self.save call to an if self.save block around the rest doesn't help, because the Person save still succeeds even when the Address one fails.) And this doesn't work because it raises the ActiveRecord::StatementInvalid exception out of the transaction block without triggering an ActiveRecord::Rollback: class Person def save_with_address(address_options = {}) transaction do save! address = Address.build(address_options) address.person = self address.save! end end end The Rails documentation specifically warns against catching the ActiveRecord::StatementInvalid inside the transaction block. I guess my first question is: why isn't this transaction block... transacting on both saves?

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• MySql Query lag time?

  - by Click Upvote

  When there are multiple PHP scripts running in parallel, each making an UPDATE query to the same record in the same table repeatedly, is it possible for there to be a 'lag time' before the table is updated with each query? I have basically 5-6 instances of a PHP script running in parallel, having been launched via cron. Each script gets all the records in the items table, and then loops through them and processes them. However, to avoid processing the same item more than once, I store the id of the last item being processed in a seperate table. So this is how my code works: function getCurrentItem() { $sql = "SELECT currentItemId from settings"; $result = $this->db->query($sql); return $result->get('currentItemId'); } function setCurrentItem($id) { $sql = "UPDATE settings SET currentItemId='$id'"; $this->db->query($sql); } $currentItem = $this->getCurrentItem(); $sql = "SELECT * FROM items WHERE status='pending' AND id > $currentItem'"; $result = $this->db->query($sql); $items = $result->getAll(); foreach ($items as $i) { //Check if $i has been processed by a different instance of the script, and if so, //leave it untouched. if ($this->getCurrentItem() > $i->id) continue; $this->setCurrentItem($i->id); // Process the item here } But despite of all the precautions, most items are being processed more than once. Which makes me think that there is some lag time between the update queries being run by the PHP script, and when the database actually updates the record. Is it true? And if so, what other mechanism should I use to ensure that the PHP scripts always get only the latest currentItemId even when there are multiple scripts running in parrallel? Would using a text file instead of the db help?

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• insert data to table based on another table C#

  - by user1017315

  I wrote a code which takes some values from one table and inserts the other table in these values.(not just these values, but also these values(this values=values from the based on table)) and I get this error: System.Data.OleDb.OleDbException (0x80040E10): value wan't given for one or more of the required parameters.` here's the code. I don't know what i've missed. string selectedItem = comboBox1.SelectedItem.ToString(); Codons cdn = new Codons(selectedItem); string codon1; int index; if (this.i != this.counter) { //take from the DataBase the matching codonsCodon1 to codonsFullName codon1 = cdn.GetCodon1(); //take the serialnumber of the last protein string connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;" + "Data Source=C:\\Projects_2012\\Project_Noam\\Access\\myProject.accdb"; OleDbConnection conn = new OleDbConnection(connectionString); conn.Open(); string last= "SELECT proInfoSerialNum FROM tblProInfo WHERE proInfoScienceName = "+this.name ; OleDbCommand getSerial = new OleDbCommand(last, conn); OleDbDataReader dr = getSerial.ExecuteReader(); dr.Read(); index = dr.GetInt32(0); //add the amino acid to tblOrderAA using (OleDbConnection connection = new OleDbConnection(connectionString)) { string insertCommand = "INSERT INTO tblOrderAA(orderAASerialPro, orderAACodon1) " + " values (?, ?)"; using (OleDbCommand command = new OleDbCommand(insertCommand, connection)) { connection.Open(); command.Parameters.AddWithValue("orderAASerialPro", index); command.Parameters.AddWithValue("orderAACodon1", codon1); command.ExecuteNonQuery(); } } } EDIT:I put a messagebox after that line: index = dr.GetInt32(0); to see where is the problem, and i get the error before that.i don't see the messagebox

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• YAHOO QUERY LANGUAGE BUG!

  - by Damiano

  Hello everybody! Today, I've started with Yahoo Query Language. I would use it to retrive stocks details, so I'm talking about Yahoo Finance. I think there is a bug on this language. This is my query: select * from yahoo.finance.quoteslist where symbol='@^GSPC' I ALWAYS get 51 results! it's impossible, take a look at: http://it.finance.yahoo.com/q/cp?s=^GSPC There are 500 results! I also tried some paging parameters. select * from yahoo.finance.quoteslist(50,30) where symbol='@^GSPC' (to get from 50 to 80) select * from yahoo.finance.quoteslist(100) where symbol='@^GSPC' (to get the first 100 results) select * from yahoo.finance.quoteslist where symbol='@^GSPC' limit 30 offset 50 but ALWAYS the last stock is: <quote symbol="BBY"> <Symbol>BBY</Symbol> <LastTradePriceOnly>41.03</LastTradePriceOnly> <LastTradeDate>5/7/2010</LastTradeDate> <LastTradeTime>4:00pm</LastTradeTime> <Change>-0.48</Change> <Open>41.35</Open> <DaysHigh>42.35</DaysHigh> <DaysLow>39.60</DaysLow> <Volume>14129531</Volume> </quote> Why do I have this kind of problem? Thank you so much for your support! (P.S. I've tested it on Yahoo YQL console)

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• Modeling complex hierarchies

  - by jdn

  To gain some experience, I am trying to make an expert system that can answer queries about the animal kingdom. However, I have run into a problem modeling the domain. I originally considered the animal kingdom hierarchy to be drawn like -animal -bird -carnivore -hawk -herbivore -bluejay -mammals -carnivores -herbivores This I figured would allow me to make queries easily like "give me all birds", but would be much more expensive to say "give me all carnivores", so I rewrote the hierarchy to look like: -animal -carnivore -birds -hawk -mammals -xyz -herbivores -birds -bluejay -mammals But now it will be much slower to query "give me all birds." This is of course a simple example, but it got me thinking that I don't really know how to model complex relationships that are not so strictly hierarchical in nature in the context of writing an expert system to answer queries as stated above. A directed, cyclic graph seems like it could mathematically solve the problem, but storing this in a relational database and maintaining it (updates) would seem like a nightmare to me. I would like to know how people typically model such things. Explanations or pointers to resources to read further would be acceptable and appreciated.

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• What is a good automated data import method for SQL Server?

  - by Joel Potter

  I'm in the process of porting some SQL Server 2005 databases to SQL Server 2008. One of these databases has an associated import application (Windows task) which uses SSIS with a DTS package to import a large dataset from an MS Access database nightly. In upgrading to SQL Server 2008, I discovered that I can't run the same console application which has been performing the imports due to the missing manageddts DLL in SQL Server 2008. It's several years old and in need of a rewrite for various reason, plus, I've been fairly unhappy with DTS in general. The original reason DTS was chosen was for speed (5 min import time compared to 30+ for ADO.NET). The format of the data to import is out of my control (the client likes Access). I would also like to be able to run the import from a machine completely separate from the server hosting SQL Server and preferably with minimal SQL features installed. Options I've considered: Creating an Access application to connect to both databases (SQL Server and Access) and perform the import (Ugh!) Revisiting ADO.NET to see if the original implementation was poorly written. Updated SSIS packages. What other technologies should I be considering for this job?

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• Primary key/foreign Key naming convention

  - by Jeremy

  In our dev group we have a raging debate regarding the naming convention for Primary and Foreign Keys. There's basically two schools of thought in our group: 1) Primary Table (Employee) Primary Key is called ID Foreign table (Event) Foreign key is called EmployeeID 2) Primary Table (Employee) Primary Key is called EmployeeID Foreign table (Event) Foreign key is called EmployeeID I prefer not to duplicate the name of the table in any of the columns (So I prefer option 1 above). Conceptually, it is consisted with a lot of the recommended practices in other languages, where you don't use the name of the object in its property names. I think that naming the foreign key EmployeeID (or Employee_ID might be better) tells the reader that it is the ID column of the Employee Table. Some others prefer option 2 where you name the primary key prefixed with the table name so that the column name is the same throughout the database. I see that point, but you now can not visually distinguish a primary key from a foreign key. Also, I think it's redundant to have the table name in the column name, because if you think of the table as an entity and a column as a property or attribute of that entity, you think of it as the ID attribute of the Employee, not the EmployeeID attribute of an employee. I don't go an ask my coworker what his PersonAge or PersonGender is. I ask him what his Age is. So like I said, it's a raging debate and we go on and on and on about it. I'm interested to get some new perspective.

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• Django: DatabaseError column does not exist

  - by Rosarch

  I'm having a problem with Django 1.2.4. Here is a model: class Foo(models.Model): # ... ftw = models.CharField(blank=True) bar = models.ForeignKey(Bar) Right after flushing the database, I use the shell: Python 2.6.6 (r266:84292, Sep 15 2010, 15:52:39) [GCC 4.4.5] on linux2 Type "help", "copyright", "credits" or "license" for more information. (InteractiveConsole) >>> from apps.foo.models import Foo >>> Foo.objects.all() Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 67, in __repr__ data = list(self[:REPR_OUTPUT_SIZE + 1]) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 82, in __len__ self._result_cache.extend(list(self._iter)) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 271, in iterator for row in compiler.results_iter(): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/compiler.py", line 677, in results_iter for rows in self.execute_sql(MULTI): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/compiler.py", line 732, in execute_sql cursor.execute(sql, params) File "/usr/local/lib/python2.6/dist-packages/django/db/backends/util.py", line 15, in execute return self.cursor.execute(sql, params) File "/usr/local/lib/python2.6/dist-packages/django/db/backends/postgresql_psycopg2/base.py", line 44, in execute return self.cursor.execute(query, args) DatabaseError: column foo_foo.bar_id does not exist LINE 1: ...t_omg", "foo_foo"."ftw", "foo_foo... What am I doing wrong here?

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• Synchronizing DataGridView (DataTable) with the DB

  - by Ezekiel Rage

  Hi! I have the following situation: there is a table in the DB that is queried when the form loads and the retrieved data is filled into a DataGridView via the DataTable underneath. After the data is loaded the user is free to modify the data (add / delete rows, modify entries). The form has 2 buttons: Apply and Refresh. The first one sends the changes to the database, the second one re-reads the data from the DB and erases any changes that have been made by the user. My question is: is this the best way to keep a DataGridView synchronized with the DB (from a users point of view)? For now these are the downsides: the user must keep track of what he is doing and must press the button every while the modifications are lost if the form is closed / app crash / ... I tried sending the changes to the DB on CellEndEdit event but then the user also needs some Undo/Redo functionality and that is ... well ... a different story. So, any suggestions?

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• using dummy row with NOT NULL to solve DEFAULT NULL

  - by Tony38

  I know having DEFAULT NULLS is not a good practice but I have many optional lookup values which are FK in the system so to solve this issue here is what i am doing: I use NOT NULL for every FK / lookup colunms. I have the first row in every lookup table which is PK id = 1 as a dummy row with just "none" in all the columns. This way I can use NOT NULL in my schema and if needed reference to the none row values PK =1 for FKs which do not have any lookup value. Is this a good design or any other work arounds? EDIT: I have: Neighborhood table Postal table. Every neighborhood has a city, so the FK can be NOT NULL. But not every postal code belongs to a neighborhood. Some do, some don't depending on the country. So if i use NOT NULL for the FK between postal and neighborhood then I will be screwed as there has to be some value entered. So what i am doing in essence is: have a row in every table to be a dummy row just to link the FKs. This way row one in neighborhood table will be: n_id = 1 name =none etc... In postal table I can have: postal_code = 3456A3 FK (city) = Moscow FK (neighborhood_id)=1 as a NOT NULL. If I don't have a dummy row in the neighborhood lookup table then I have to declare FK (neighborhood_id) as a Default null column and store blanks in the table. This is an example but there is a huge number of values which will have blanks then in many tables.

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• What is the fastest way to find duplicates in multiple BIG txt files?

  - by user2950750

  I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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• Saving tree-structures in Databases

  - by Nina Null

  Hello everyone. I use Hibernate/Spring and a MySQL Database for my data management. Currently I display a tree-structure in a JTable. A tree can have several branches, in turn a branch can have several branches (up to nine levels) again, or having leaves. Lately I have performanceproblemes, as soon as I want to create new branches on deeper levels. At this time a branch has a foreign key to its parent. The domainobject has access to its parent by calling getParent(), which returns the parent-branch. The deeper the level, the longer it takes to create a new branch. Microbenchmark results for creating a new branch are like: Level 1: 32 ms. Level 3: 80 ms. Level 9: 232 ms. Obviously the level (which means the number of parents) is responsible for this. So I wanted to ask, if there are any appendages to work around this kind of problem. I don’t understand why Hibernate needs to know about the whole object tree (all parents until the root) while creating a new branch. But as far as I know this can be the only reason for the delay while creating a new branch, because a branch doesn’t have any other relations to any other objects. I would be very thankful for any workarounds or suggestions. greets, jambusa

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• SQL Databases and table design/organization

  - by John McMullen

  (NOOB disclaimer) I'm working on a system (a type of map), that is accessed mostly via 3 fields: ID (auto incremented), X coordinate, and Y coordinate. As it is right now, i have all data on the map, stored in 1 table. Whenever the map display is loaded it simply queries the database for contents in x and y, and the DB gives the data (other fields in the same entry). If an item on the map is doing something, it has a flag saying its doing something, and then has an ID of the action in another table holding that type of 'actions'. Essentially, for all map data, its stored in 1 table. All actions of a certain type are stored in their own table. I'm a noob, and i'm wondering what the most effective/efficient structure for such a design? (a map that has items, and each item has stats/actions). I'm using PHP atm, using standard SQL queries to get my data. Should i split up the tables so that there are only x number of entries on a table? (coord range limits)? Should it just keep growing and growing? There's a lot of queries to the table... so just tryin to see what is best :/

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• A GUID as the MySQL table's Primary Key or as a separate column

  - by Ben

  I have a multi-process program that performs, in a 2 hour period, 5-10 million inserts to a 34GB table within a single Master/Slave MySQL setup (plus an equal number of reads in that period). The table in question has only 5 fields and 3 (single field) indexes. The primary key is auto-incrementing. I am far from a DBA, but the database appears to be crippled during this two hour period. So, I have a couple of general questions. 1) How much bang will I get out of batching these writes into units of 10? Currently, I am writing each insert serially because, after writing, I immediately need to know, in my program, the resulting primary key of each insert. The PK is the only unique field presently and approximating the order of insertion with something like a Datetime field or a multi-column value is not acceptable. If I perform a bulk insert, I won't know these IDs, which is a problem. So, I've been thinking about turning the auto-increment primary key into a GUID and enforcing uniqueness. I've also been kicking around the idea of creating a new column just for the purposes of the GUID. I don't really see the what that achieves though, that the PK approach doesn't already offer. As far as I can tell, the big downside to making the PK a randomly generated number is that the index would take a long time to update on each insert (since insertion order would not be sequential). Is that an acceptable approach for a table that is taking this number of writes? Thanks, Ben

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• Draw a comparison between an integer in a specific row and a count

  - by XCoderX

  This is a follow-up question to this one: Check for specific integer in a row WHERE user = $name I want a user to be able to comment on my site for exactly five times a day. After this five times, the user has to wait 24 hours. In order to accomplish that I raise a counter in my MYSQL database, right next to the user. So where the name of the user is, there is where the counter gets raised. When it reaches 5 it should stop counting and reset after 24 hours. In order to check the time I use a timestamp. I check if the timestamp is older than 24 hours. If that is the case, the counter gets reseted (-5) and the user can comment again. In order to do that, I use the following code, however it never stops at five, my guess is that my comparison is wrong somehow: $counter = "SELECT FROM table VALUES CommentCounterReset WHERE Name = '$name'"; if(!isset($_SESSION['ts'])); { $_SESSION['ts'] = time(); } if ($counter >= 5) { if (time() - $_SESSION['ts'] <= 60*60*24){ echo "You already wrote five comments."; } else { $sql = "UPDATE table SET CommentCounterReset = CommentCounterReset-5 WHERE Name = '$name'"; } } else { $sql = "UPDATE table SET CommentCounterReset = CommentCounterReset+1 WHERE Name = '$name'"; echo "Your comment has been added."; }

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