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  • SQL Joins Excluding Data

    - by Andrew
    Say I have three tables: Fruit (Table 1) ------ Apple Orange Pear Banana Produce Store A (Table 2 - 2 columns: Fruit for sale => Price) ------------------------- Apple => 1.00 Orange => 1.50 Pear => 2.00 Produce Store B (Table 3 - 2 columns: Fruit for sale => Price) ------------------------ Apple => 1.10 Pear => 2.50 Banana => 1.00 If I would like to write a query with Column 1: the set of fruit offered at Produce Store A UNION Produce Store B, Column 2: Price of the fruit at Produce Store A (or null if that fruit is not offered), Column 3: Price of the fruit at Produce Store B (or null if that fruit is not offered), how would I go about joining the tables? I am facing a similar problem (with more complex tables), and no matter what I try, if the "fruit" is not at "produce store a" but is at "produce store b", it is excluded (since I am joining produce store a first). I have even written a subquery to generate a full list of fruits, then left join Produce Store A, but it is still eliminating the fruits not offered at A. Any Ideas?

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  • Comparison of music data

    - by Christian P.
    Hey I am looking for theory, algorithms and similar for how to compare music. More specifically, I am looking into how to dupecheck music tracks that have different bitrates or perhaps slightly different variations (radio vs album version), but otherwise sound the same. Use cases for this include services such as Grooveshark, Youtube, etc. where they get a lot of duplicate tracks. I am also interested in text comparisons (Britney Spers vs Britney Spears, how far they deviate, etc.) although this is secondary and I already have some sources to go on in this area. I am mostly interested in codec-agnostic comparison techniques and algoritms (assuming a "raw" stream), but codec-specific resources are appreciated. I am aware of projects such as musicbrainz.org, but have not investigated it further, and would be interested if such projects could be of help in this endeavor.

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  • insertNewObjectForEntityForName: inManagedObjectContext: returning NSNumber bug?

    - by beinstein
    I'm relatively well versed in CoreData and have been using it for several years with little or no difficulty. All of a sudden I'm now dumbfounded by an error. For the life of me, I can't figure out why insertNewObjectForEntityForName:inManagedObjectContext: is all of a sudden returning some sort of strange instance of NSNumber. GDB says the returned object is of the correct custom subclass of NSManagedObject, but when I go to print a description of the NSManagedObject itself, I get the following error: *** -[NSCFNumber objectID]: unrecognized selector sent to instance 0x3f26f50 What's even stranger, is that I'm able to set some relationships and attributes using setValue:forKey: and all is good. But when I try to set once specific relationship, I get this error: *** -[NSCFNumber entity]: unrecognized selector sent to instance 0x3f26f50 Has anyone ever encountered anything like this before? I've tried clean all targets, restarting everything, even changing the model to the relationship in question is a to-one instead of a to-many. Nothing makes any difference.

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  • Having problem loading data from AppDelegate using UITableView into a flip view, loads first view bu

    - by Ms. Ryann
    AppDelegate: @implementation Ripe_ProduceGuideAppDelegate -(void)applicationDidFinishLaunching:(UIApplication *)application { Greens *apricot = [[Greens alloc] init]; apricot.produceName = @"Apricot"; apricot.produceSight = @"Deep orange or yellow orange in appearance, may have red tinge, no marks or bruises. "; apricot.produceTouch = @"Firm to touch and give to gentle pressure, plump."; apricot.produceSmell = @"Should be Fragrant"; apricot.produceHtoP = @"raw, salads, baked, sauces, glazes, desserts, poached, stuffing."; apricot.produceStore = @"Not ripe: place in brown paper bag, at room temperature and out of direct sunlight, close bag for 2 - 3 days. Last for a week. Warning: Only refrigerate ripe apricots."; apricot.produceBest = @"Spring & Summer"; apricot.producePic = [UIImage imageNamed:@"apricot.jpg"]; Greens *artichoke = [[Greens alloc] init]; artichoke.produceName = @"Artichoke"; artichoke.produceSight = @"Slightly glossy dark green color and sheen, tight petals that are not be too open, no marks, no brown petals or dried out look. Stem should not be dark brown or black."; artichoke.produceTouch = @"No soft spots"; artichoke.produceSmell = @" Should not smell"; artichoke.produceHtoP = @"steam, boil, grill, saute, soups"; artichoke.produceStore = @"Stand up in vase of cold water, keeps for 2 -3 days. Or, place in refrigerator loose without plastic bag. May be frozen, if cooked but not raw."; artichoke.produceBest = @"Spring"; artichoke.producePic = [UIImage imageNamed:@"artichoke.jpg"]; self.produce = [[NSMutableArray alloc] initWithObjects:apricot, artichoke, nil]; [apricot release]; [artichoke release]; FirstView: @implementation ProduceView -(id)initWithIndexPath: (NSIndexPath *)indexPath { if (self == [super init] ){ index = indexPath; } return self; } -(void)viewDidLoad { Ripe_ProduceGuideAppDelegate *delegate = (Ripe_ProduceGuideAppDelegate *) [[UIApplication sharedApplication] delegate]; Greens *thisProduce = [delegate.produce objectAtIndex:index.row]; self.title = thisProduce.produceName; sightView.text = thisProduce.produceSight; touchView.text = thisProduce.produceTouch; smellView.text = thisProduce.produceSmell; picView.image = thisProduce.producePic; } FlipView: @implementation FlipsideViewController @synthesize flipDelegate; -(id)initWithIndexPath: (NSIndexPath *)indexPath { if ( self == [super init]) { index = indexPath; } return self; } -(void)viewDidLoad { Ripe_ProduceGuideAppDelegate *delegate = (Ripe_ProduceGuideAppDelegate *) [[UIApplication sharedApplication] delegate]; Greens*thisProduce = [delegate.produce objectAtIndex:index.row]; self.title = thisProduce.produceName; bestView.text = thisProduce.produceBest; htopView.text = thisProduce.produceHtoP; storeView.text = thisProduce.produceStore; picView.image = thisProduce.producePic; } *the app works, the flip view for Artichoke shows the information for Apricot. Been working on it for two days. I have been working with iPhone apps for two months now and would very much appreciate any assistance with this problem. Thank you very much.

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  • Avoid the collapsing effect on TreeView after updating data

    - by Manolete
    I have a TreeView used to display events. It works great, however every time new events are coming in and populating the tree collapse the tree again to the original position. That is very annoying when the refresh time is less than 1 second and it does not allow the user to interact with the items of the tree. Is there any way to avoid this behaviour? <TreeView Margin="1" BorderThickness="0" Name="eventsTree" ItemsSource="{Binding EventAlertContainers}" Background="#00000000" ScrollViewer.VerticalScrollBarVisibility="Auto" FontSize="14" VirtualizingStackPanel.IsVirtualizing="True"> <TreeView.Resources> <HierarchicalDataTemplate DataType="{x:Type C:EventAlertContainer}" ItemsSource="{Binding EventAlerts}"> <StackPanel Orientation="Horizontal"> <Image Width="20" Height="20" Margin="3,0" Source="Resources\Process_info_32.png" /> <TextBlock FontWeight="Bold" FontSize="16" Text="{Binding Description}" /> </StackPanel> </HierarchicalDataTemplate> <HierarchicalDataTemplate DataType="{x:Type C:EventAlert}" ItemsSource="{Binding Events}"> <StackPanel Orientation="Horizontal"> <Image Width="20" Height="20" Margin="0,0" Source="Resources\clock2_32.jpg" /> <TextBlock FontWeight="DemiBold" FontSize="14" Text="{Binding Name}" /> </StackPanel> </HierarchicalDataTemplate> <HierarchicalDataTemplate DataType="{x:Type C:Event}"> <StackPanel Orientation="Horizontal"> <Image Width="20" Height="20" Margin="0,0" Source="Resources\Task_32.png" /> <StackPanel Orientation="Vertical"> <TextBlock FontSize="12" Text="{Binding Name}" /> </StackPanel> </StackPanel> </HierarchicalDataTemplate> </TreeView.Resources> </TreeView>

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  • Transfer files using java

    - by markovuksanovic
    I need to transfer lots of small files to a remote computer within my java program. I was wondering if somebody could suggest the best way to do so... I need to transfer lots of small files and it has to be really fast. Should I use some existing protocol implementation? maybe ftp? One important thing is that most files would be the same all the time, or the difference would be minor so I was thinking of using git for that purpose. Does anyone have experience with sth like this?

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  • UICollectionView with one static cell and N dynamic ones from a fetchresultscontroller exception

    - by nflacco
    I'm trying to make a UITableView that shows a blog post and comments for that post. My setup is a tableview in storyboard with two dynamic prototype cells. The first cell is for the post and should never change. The second cell represents the 0 to N comments. My cellForRowAtIndexPath method shows the post cell properly, but fails to get the comment at the given index path (though if I comment out the fetch I get the appropriate number of comment cells with a green background that I set as a visual debug thing). let comment = fetchedResultController.objectAtIndexPath(indexPath) as Comment I get the following exception on this line: 2014-08-24 15:06:40.712 MessagePosting[21767:3266409] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 1 beyond bounds [0 .. 0]' *** First throw call stack: ( 0 CoreFoundation 0x0000000101aa43e5 __exceptionPreprocess + 165 1 libobjc.A.dylib 0x00000001037f9967 objc_exception_throw + 45 2 CoreFoundation 0x000000010198f4c3 -[__NSArrayM objectAtIndex:] + 227 3 CoreData 0x00000001016e4792 -[NSFetchedResultsController objectAtIndexPath:] + 162 Section and cell setup: override func tableView(tableView: UITableView!, numberOfRowsInSection section: Int) -> Int { // #warning Incomplete method implementation. // Return the number of rows in the section. switch section { case 0: return 1 default: if let realPost:Post = post { return fetchedResultController.sections[0].numberOfObjects } else { return 0 } } } override func tableView(tableView: UITableView!, cellForRowAtIndexPath indexPath: NSIndexPath!) -> UITableViewCell! { switch indexPath.section { case 0: let cell = tableView.dequeueReusableCellWithIdentifier(postViewCellIdentifier, forIndexPath: indexPath) as UITableViewCell cell.backgroundColor = lightGrey if let realPost:Post = self.post { cell.textLabel.text = realPost.text } return cell default: let cell = tableView.dequeueReusableCellWithIdentifier(commentCellIdentifier, forIndexPath: indexPath) as UITableViewCell cell.backgroundColor = UIColor.greenColor() let comment = fetchedResultController.objectAtIndexPath(indexPath) as Comment // <---------------------------- :( cell.textLabel.text = comment.text return cell } } FRC: func controllerDidChangeContent(controller: NSFetchedResultsController!) { tableView.reloadData() } func getFetchedResultController() -> NSFetchedResultsController { fetchedResultController = NSFetchedResultsController(fetchRequest: taskFetchRequest(), managedObjectContext: managedObjectContext, sectionNameKeyPath: nil, cacheName: nil) return fetchedResultController } func taskFetchRequest() -> NSFetchRequest { if let realPost:Post = self.post { let fetchRequest = NSFetchRequest(entityName: "Comment") let sortDescriptor = NSSortDescriptor(key: "date", ascending: false) fetchRequest.predicate = NSPredicate(format: "post = %@", realPost) fetchRequest.sortDescriptors = [sortDescriptor] return fetchRequest } else { return NSFetchRequest(entityName: "") } }

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  • Django: many-to-one fields and data integrity

    - by John
    Let's say that I have a Person who runs an inventory system. Each Person has some Cars, and each Car has a very large number of Parts (thousands, let's say). A Person, Bob, uses a Django form to create a Car. Now, Bob goes to create some Parts. It is only at the form level that Django knows that the Parts belong to some specific Car, and that the Parts.ForeignKey(Car) field should only have a specific Car as a choice. When creating a Part, you have to mess with the form's constructor or similar in order to limit the choice of Cars to only the cars owned by Bob. It does not seem proper that to enforce this ownership at the form level. It seems that other users' Cars must be inaccessible to anyone but the owner of the Car. What do you all think about this, and is there any way to enforce this?

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  • Branchless memory manager?

    - by Richard Fabian
    Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concurrent, in-order CPU, and cache friendly development. Edit: by branchless I mean without doing direct or indirect function calls, and without using ifs. I've been thinking that I can probably implement something that first changes the requested size to zero for false calls, but haven't really got much more than that. I feel that it's not impossible, but the other aspect of this exercise is then profiling it on said "unfriendly" processors to see if it's worth trying as hard as this to avoid branching.

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  • enCapsa -what is it and what is used for?

    - by agnieszka
    It may not be a pure programming question but I'm looking for information about enCapsa. Do you know what it is, have you ever used it? I'm reading some papers about it but I can't really see how it works and what it can be used for in an IT company (and this is what i am supposed to find out).

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  • How to do an fetch request with expressions like this on the iPhone?

    - by dontWatchMyProfile
    The documentation has an example on how to retrieve simple values only, rather than managed objects. This remembers a lot SQL using aliases and functions to only retrieve calculated values. So, actually pretty geeky stuff. To get the minimum date from a bunch of records, this is used on the mac: NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:context]; [request setEntity:entity]; // Specify that the request should return dictionaries. [request setResultType:NSDictionaryResultType]; // Create an expression for the key path. NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@"creationDate"]; // Create an expression to represent the minimum value at the key path 'creationDate' NSExpression *minExpression = [NSExpression expressionForFunction:@"min:" arguments:[NSArray arrayWithObject:keyPathExpression]]; // Create an expression description using the minExpression and returning a date. NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init]; // The name is the key that will be used in the dictionary for the return value. [expressionDescription setName:@"minDate"]; [expressionDescription setExpression:minExpression]; [expressionDescription setExpressionResultType:NSDateAttributeType]; // Set the request's properties to fetch just the property represented by the expressions. [request setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]]; // Execute the fetch. NSError *error; NSArray *objects = [managedObjectContext executeFetchRequest:request error:&error]; if (objects == nil) { // Handle the error. } else { if ([objects count] > 0) { NSLog(@"Minimum date: %@", [[objects objectAtIndex:0] valueForKey:@"minDate"]; } } [expressionDescription release]; [request release]; Nice, I though - but having a deep look into NSExpression -expressionForFunction:arguments: it turns out that iPhone OS does NOT support the min: function. Well, probably there's a nifty way to use an own function for this kind of stuff on the iPhone as well? Because on thing I'm already worrying about is, how I'm gonna sort a table based on the calculated distance of targets on a map (location-based stuff).

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  • Problems in getting data from CFStreamCreatePairWithSocketToHost

    - by gkedmi
    Hi I'm building an iPhoe app with a socket to a PC app , I need to get an image from this PC app. It's my first time using "CFStreamCreatePairWithSocketToHost".After I establish the socket with "NSOperation" I call CFStreamClientContext streamContext = {0, self, NULL, NULL, NULL}; BOOL success = CFReadStreamSetClient(myReadStream, kMyNetworkEvents,MyStreamCallBack,&streamContext); CFReadStreamScheduleWithRunLoop(myReadStream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode); then I call CFWriteStreamWrite(myWriteStream, &writeBuffer, 3); // Open read stream. if (!CFReadStreamOpen(myReadStream)) { // Notify error } . . . while(!cancelled && !finished) { SInt32 result = CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0.25, NO); if (result == kCFRunLoopRunStopped || result == kCFRunLoopRunFinished) { break; } if (([NSDate timeIntervalSinceReferenceDate] - _lastRead) MyConnectionTimeout) { // Call timed out cancelled = YES; break; } // Also handle stream status CFStreamStatus status = CFReadStreamGetStatus(myReadStream); } and then when I get "kCFStreamEventHasBytesAvailable" I use while (CFReadStreamHasBytesAvailable(myReadStream)) { CFReadStreamRead(myReadStream, readBuffer, 1000); //and buffer the the bytes } It's unpredictable , sometimes I get the whole picture , sometime I got just part of it , and I can't understand what make the different. can someone has an idea what is wrong here? thanks

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  • Updating a Data Source with a Dataset

    - by Paul
    Hi, I need advice. I have asp.net web service and winforms client app. Client call this web method and get dataset. 1. [WebMethod] 2. public DataSet GetSecureDataSet(string id) 3. { 4. 5. 6. SqlConnection conn = null; 7. SqlDataAdapter da = null; 8. DataSet ds; 9. try 10. { 11. 12. string sql = "SELECT * FROM Tab1"; 13. 14. string connStr = WebConfigurationManager.ConnectionStrings["Employees"].ConnectionString; 15. 16. conn = new SqlConnection(connStr); 17. conn.Open(); 18. 19. da = new SqlDataAdapter(sql, conn); 20. 21. ds = new DataSet(); 22. da.Fill(ds, "Tab1"); 23. 24. return ds; 25. } 26. catch (Exception ex) 27. { 28. throw ex; 29. } 30. finally 31. { 32. if (conn != null) 33. conn.Close(); 34. if (da != null) 35. da.Dispose(); 36. } 37. } After he finish work he call this update web method. He can add, delete and edit rows in table in dataset. [WebMethod] public bool SecureUpdateDataSet(DataSet ds) { SqlConnection conn = null; SqlDataAdapter da = null; SqlCommand cmd = null; try { DataTable delRows = ds.Tables[0].GetChanges(DataRowState.Deleted); DataTable addRows = ds.Tables[0].GetChanges(DataRowState.Added); DataTable editRows = ds.Tables[0].GetChanges(DataRowState.Modified); string sql = "UPDATE * FROM Tab1"; string connStr = WebConfigurationManager.ConnectionStrings["Employees"].ConnectionString; conn = new SqlConnection(connStr); conn.Open(); cmd = new SqlCommand(sql, conn); da = new SqlDataAdapter(sql, conn); if (addRows != null) { da.Update(addRows); } if (delRows != null) { da.Update(delRows); } if (editRows != null) { da.Update(editRows); } return true; } catch (Exception ex) { throw ex; } finally { if (conn != null) conn.Close(); if (da != null) da.Dispose(); } } Code on client side 1. //on client side is dataset bind to datagridview 2. Dataset ds = proxy.GetSecureDataSet(""); 3. ds.AcceptChanges(); 4. 5. //edit dataset 6. 7. 8. //get changes 9. DataSet editDataset = ds.GetChanges(); 10. 11. //call update webmethod 12. proxy.SecureUpdateDataSet(editDataSet) But it finish with this error : System.Web.Services.Protocols.SoapException: Server was unable to process request. --- System.InvalidOperationException: Update requires a valid UpdateCommand when passed DataRow collection with modified rows. at WebService.Service.SecureUpdateDataSet(DataSet ds) in D:\Diploma.Work\WebService\Service1.asmx.cs:line 489 Problem is with SQL Commad, client can add, delete and insert row, how can write a corect SQL command.... any advice please? Thank you

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  • Encode JSON data into another JSON object

    - by jburns20
    I have a JSON string that I would like to include as a value in a larger JSON object that I am creating from an array. How can I create the larger JSON object without php escaping the string, and without having to decode the previously encoded string? For example, if my JSON string is: $encoded_already = '{"encoded_key": "encoded_value"}'; And I would like to include it in my array and json_encode() it: $new_array = array( "some_other_key" => $some_value, "premade_data" => $encoded_already ); $output = json_encode($new_array); but I want to have the $encoded_already string be included as actual JSON, not just an escaped string.

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  • Merging two SQLite database files (C# .NET)

    - by CODe
    Hello all, I'm using C#/.NET with the C# wrapper for SQLite. I'm attempting to merge two SQLite databases together while excluding duplicates. I found this, which is referenced from a few different forum questions. http://old.nabble.com/Attempting-to-merge-large-databases-td18131366.html Would I run the following queries in my SQLite configuration as listed below? attach 'c:\test\b.db3' as toMerge; insert into AuditRecords select * from toMerge.AuditRecords; My main question is whether the above will remove duplicates, and if it doesn't, is there a merge or some other command I can use? Thanks very much!

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  • Perl, regex, extract data from a line

    - by perlnoob
    Im trying to extract part of a line with perl use strict; use warnings; # Set path for my.txt and extract datadir my @myfile = "C:\backups\MySQL\my.txt"; my @datadir = ""; open READMYFILE, @myfile or die "Error, my.txt not found.\n"; while (<READMYFILE>) { # Read file and extract DataDir path if (/C:\backups/gi) { push @datadir, $_; } } # ensure the path was found print @datadir . " \n"; Basically at first im trying to set the location of the my.txt file. Next im trying to read it and pull part of the line with regex. The error Im getting is: Unrecognized escape \m passed through at 1130.pl line 17. I took a look at http://stackoverflow.com/questions/1040657/how-can-i-grab-multiple-lines-after-a-matching-line-in-perl to get an idea of how to read a file and match a line within it, however im not 100% sure I'm doing this right or in the best way. I also seem to produce the error: Error, my.txt not found. But the file does exist in the folder C:\backups\MySQL\

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  • Get percentiles of data-set with group by month

    - by Cylindric
    Hello, I have a SQL table with a whole load of records that look like this: | Date | Score | + -----------+-------+ | 01/01/2010 | 4 | | 02/01/2010 | 6 | | 03/01/2010 | 10 | ... | 16/03/2010 | 2 | I'm plotting this on a chart, so I get a nice line across the graph indicating score-over-time. Lovely. Now, what I need to do is include the average score on the chart, so we can see how that changes over time, so I can simply add this to the mix: SELECT YEAR(SCOREDATE) 'Year', MONTH(SCOREDATE) 'Month', MIN(SCORE) MinScore, AVG(SCORE) AverageScore, MAX(SCORE) MaxScore FROM SCORES GROUP BY YEAR(SCOREDATE), MONTH(SCOREDATE) ORDER BY YEAR(SCOREDATE), MONTH(SCOREDATE) That's no problem so far. The problem is, how can I easily calculate the percentiles at each time-period? I'm not sure that's the correct phrase. What I need in total is: A line on the chart for the score (easy) A line on the chart for the average (easy) A line on the chart showing the band that 95% of the scores occupy (stumped) It's the third one that I don't get. I need to calculate the 5% percentile figures, which I can do singly: SELECT MAX(SubQ.SCORE) FROM (SELECT TOP 45 PERCENT SCORE FROM SCORES WHERE YEAR(SCOREDATE) = 2010 AND MONTH(SCOREDATE) = 1 ORDER BY SCORE ASC) AS SubQ SELECT MIN(SubQ.SCORE) FROM (SELECT TOP 45 PERCENT SCORE FROM SCORES WHERE YEAR(SCOREDATE) = 2010 AND MONTH(SCOREDATE) = 1 ORDER BY SCORE DESC) AS SubQ But I can't work out how to get a table of all the months. | Date | Average | 45% | 55% | + -----------+---------+-----+-----+ | 01/01/2010 | 13 | 11 | 15 | | 02/01/2010 | 10 | 8 | 12 | | 03/01/2010 | 5 | 4 | 10 | ... | 16/03/2010 | 7 | 7 | 9 | At the moment I'm going to have to load this lot up into my app, and calculate the figures myself. Or run a larger number of individual queries and collate the results.

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  • Discover periodic patterns in a large data-set

    - by Miner
    I have a large sequence of tuples on disk in the form (t1, k1) (t2, k2) ... (tn, kn) ti is a monotonically increasing timestamp and ki is a key (assume a fixed length string if needed). Neither ti nor ki are guaranteed to be unique. However, the number of unique tis and kis is huge (millions). n itself is very large (100 Million+) and the size of k (approx 500 bytes) makes it impossible to store everything in memory. I would like to find out periodic occurrences of keys in this sequence. For example, if I have the sequence (1, a) (2, b) (3, c) (4, b) (5, a) (6, b) (7, d) (8, b) (9, a) (10, b) The algorithm should emit (a, 4) and (b, 2). That is a occurs with a period of 4 and b occurs with a period of 2. If I build a hash of all keys and store the average of the difference between consecutive timestamps of each key and a std deviation of the same, I might be able to make a pass, and report only the ones that have an acceptable std deviation(ideally, 0). However, it requires one bucket per unique key, whereas in practice, I might have very few really periodic patterns. Any better ways?

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  • C++ stack for multiple data types (RPN vector calculator)

    - by Arrieta
    Hello: I have designed a quick and basic vector arithmetic library in C++. I call the program from the command line when I need a rapid cross product, or angle between vectors. I don't use Matlab or Octave or related, because the startup time is larger than the computation time. Again, this is for very basic operations. I am extending this program, and I will make it work as an RPN calculator, for operations of the type: 1 2 3 4 5 6 x out: -3 6 -3 (give one vector, another vector, and the "cross" operator; spit out the cross product) The stack must accept 3d vectors or scalars, for operations like: 1 2 3 2 * out: 2 4 6 The lexer and parser for this mini-calculator are trivial, but I cannot seem to think of a good way for creating the internal stack. How would you create a stack of for containing vectors or doubles (I rolled up my own very simple vector class - less than one hundred lines and it does everything I need). How can I create a simple stack which accepts elements of class Vector or type double? Thank you.

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  • Checking if MySQL Database data does not exist

    - by Ben Sinclair
    I have my songs set-up in my MySQL database. Each song is is either assigned multiple locations or has no locations at all. Only the songs that either have no locations assigned in the database or have the location assigned to the ones specified below should be pulled from the database. Hopefully when you understand my query below it will make sense SELECT s.* FROM roster_songs AS s LEFT JOIN roster_songs_locations AS sl ON sl.song_id = s.id WHERE EXISTS ( SELECT sl2.* FROM roster_songs_locations AS sl2 WHERE s.id != sl2.song_id ) OR ( sl.location_id = '88fb5f94-aaa6-102c-a4fa-1f05bca0eec6' OR sl.location_id = '930555b0-a251-102c-a245-1559817ce81a' ) GROUP BY s.id The query almost works except it pulls out of the database songs that are assigned to sl.location_id's that aren't specified in the above query. I think it has something to do with my EXISTS code picking them up... Any ideas how I can get this to work?

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