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• SQL Is it possible to setup a column that will contain a value dependent on another column?

  - by Wesley

  I have a table (A) that lists all bundles created off a machine in a day. It lists the date created and the weight of the bundle. I have an ID column, a date column, and a weight column. I also have a table (B) that holds the details related to that machine for the day. In that table (B), I want a column that lists a sum of weights from the other table (A) that the dates match on. So if the machine runs 30 bundles in a day, I'll have 30 rows in table (A) all dated the same day. In table (B) I'll have 1 row detailing other information about the machine for the day plus the column that holds the total bundle weight created for the day. Is there a way to make the total column in table (B) automatically adjust itself whenever a row is added to table (A)? Is this possible to do in the table schema itself rather than in an SQL statement each time a bundle is added? If it's not, what sort of SQL statement do I need? Wes

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• SQL Design: representing a default value with overrides?

  - by Mark Harrison

  I need a sparse table which contains a set of "override" values for another table. I also need to specify the default value for the items overridden. For example, if the default value is 17, then foo,bar,baz will have the values 17,21,17: table "things" table "xvalue" name stuff name xval ---- ----- ---- ---- foo ... bar 21 bar ... baz ... If I don't care about a FK from xvalue.name - things.name, I could simply put a "DEFAULT" name: table "xvalue" name xval ---- ---- DEFAULT 17 bar 21 But I like having a FK. I could have a separate default table, but it seems odd to have 2x the number of tables. table "xvalue_default" xval ---- 17 table "xvalue" name xval ---- ---- bar 21 I could have a "defaults table" tablename attributename defaultvalue xvalue xval 17 but then I run into type issues on defaultvalue. My operations guys prefer as compact a representation as possible, so they can most easily see the "diff" or deviations from the default. What's the best way to represent this, including the default value? This will be for Oracle 10.2 if that makes a difference.

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• Is it possible to declare multiple static variable with same name in a single C file?

  - by Mohammed Khalid Kherani

  Hi Experts, Is it possible to declare multiple static variables of same name in a single C file with different scopes? I wrote a simple programme to check this and in gcc it got compiled and worked fine. code: static int sVar = 44; void myPrint2() { printf("sVar = %d\n", sVar++); } void myPrint() { static int sVar =88; printf("sVar = %d\n", sVar++); } int main(void) { static int sVar = 55; int i = 0; for (i = 0; i < 5; i++) myPrint(); printf("sVar = %d\n", sVar); myPrint2(); return(0); } Now my question is since all "static" variable will reside in same section (.data) then how we can have multiple variable with same name in one section? I used objdump to check the different section and found that all Static variables (sVar) were in .data section but with different names 0804960c l O .data 00000004 sVar 08049610 l O .data 00000004 sVar.1785 08049614 l O .data 00000004 sVar.1792 Why compiler is changing the name of variables (since C doesnt support name mangling)? Thanks in advance.

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• named_scope + average is causing the table to be specified more then once in the sql query run on po

  - by hadees

  I have a named scopes like so... named_scope :gender, lambda { |gender| { :joins => {:survey_session => :profile }, :conditions => { :survey_sessions => { :profiles => { :gender => gender } } } } } and when I call it everything works fine. I also have this average method I call... Answer.average(:rating, :include => {:survey_session => :profile}, :group => "profiles.career") which also works fine if I call it like that. However if I were to call it like so... Answer.gender('m').average(:rating, :include => {:survey_session => :profile}, :group => "profiles.career") I get... ActiveRecord::StatementInvalid: PGError: ERROR: table name "profiles" specified more than once : SELECT avg("answers".rating) AS avg_rating, profiles.career AS profiles_career FROM "answers" LEFT OUTER JOIN "survey_sessions" survey_sessions_answers ON "survey_sessions_answers".id = "answers".survey_session_id LEFT OUTER JOIN "profiles" ON "profiles".id = "survey_sessions_answers".profile_id INNER JOIN "survey_sessions" ON "survey_sessions".id = "answers".survey_session_id INNER JOIN "profiles" ON "profiles".id = "survey_sessions".profile_id WHERE ("profiles"."gender" = E'm') GROUP BY profiles.career Which is a little hard to read but says I'm including the table profiles twice. If I were to just remove the include from average it works but it isn't really practical because average is actually being called inside a method which gets passed the scoped. So there is some times gender or average might get called with out each other and if either was missing the profile include it wouldn't work. So either I need to know how to fix this apparent bug in Rails or figure out a way to know what scopes were applied to a ActiveRecord::NamedScope::Scope object so that I could check to see if they have been applied and if not add the include for average.

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• How do I construct a more complex single LINQ to XML query?

  - by Cyberherbalist

  I'm a LINQ newbie, so the following might turn out to be very simple and obvious once it's answered, but I have to admit that the question is kicking my arse. Given this XML: <measuresystems> <measuresystem name="SI" attitude="proud"> <dimension name="mass" dim="M" degree="1"> <unit name="kilogram" symbol="kg"> <factor name="hundredweight" foreignsystem="US" value="45.359237" /> <factor name="hundredweight" foreignsystem="Imperial" value="50.80234544" /> </unit> </dimension> </measuresystem> </measuresystems> I can query for the value of the conversion factor between kilogram and US hundredweight using the following LINQ to XML, but surely there is a way to condense the four successive queries into a single complex query? XElement mss = XElement.Load(fileName); IEnumerable<XElement> ms = from el in mss.Elements("measuresystem") where (string)el.Attribute("name") == "SI" select el; IEnumerable<XElement> dim = from e2 in ms.Elements("dimension") where (string)e2.Attribute("name") == "mass" select e2; IEnumerable<XElement> unit = from e3 in dim.Elements("unit") where (string)e3.Attribute("name") == "kilogram" select e3; IEnumerable<XElement> factor = from e4 in unit.Elements("factor") where (string)e4.Attribute("name") == "pound" && (string)e4.Attribute("foreignsystem") == "US" select e4; foreach (XElement ex in factor) { Console.WriteLine ((string)ex.Attribute("value")); }

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• php sessions in database only writing part of information to the table...

  - by Ronedog

  I'm having difficulty figuring out what's going on here, hoping some one can help me out. I have been using php, mysql storing my session information in the database. The app is only running on localhost, vista. In the php.ini file I commented out the "session.save_handler = files" line and am using a php class to handle the session writes/reads, etc. My login process is this: Submit login credentials via login.php. login.php calls loginprocess.php. loginprocess.php verifies user, and if valid starts a new session and adds data to the session vars, then it redirects to index.php. Here's the problem. the loginprocess.php page has a bunch of session vars that get set like $_SESSION['account_id'] = $account_id; etc. but when I go to index.php and do a var_dump($_SESSION) it just says "array() empty". However, if I do a var_dump($_SESSION) in loginprocess.php, just before the redirection line header("Location: ../index.php"); then it shows all the data in the session variable. If I look in the database where the session information is stored, there is data in the session_id field, created_ts field, and expires field, but the session_data field has nothing inside of it and in the past this is the field where all my session data was stored. How could I be able to var_dump the session in loginprocess.php, but the data not exist in the db table, is it using some kind of caching? I cleared my cookies, etc...but no change. Why is the session_id, being written to the table, but the actual session data is not? Any ideas are appreciated. Thanks.

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• Suppose i have an HTML table. How do I use JQuery events on this?

  - by alex

  <table> <tr class="myRow"><td class="col1"></td><td class="col2"></td></tr> <tr class="myRow"><td class="col1"></td><td class="col2"></td></tr> <tr class="myRow"><td class="col1"></td><td class="col2"></td></tr> <tr class="myRow"><td class="col1"></td><td class="col2"></td></tr> <tr class="myRow"><td class="col1"></td><td class="col2"></td></tr> </table> How do I make the appropriate col1 fill with the letters "ABC" when the user rollovers the row? And then disappear the "ABC" when the user moves the mouse away from that row? So far, I got this. I solved it. $(".ep").hover(function(){ $(this).find('td.playButtonCol').html('PLAY'); },function(){ $(this).find('td.playButtonCol').html(''); });

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• Finding Specific Descendant Nodes With XSL:Key

  - by DBA_Alex

  Given the following code: <database> <table name="table1"> <column name="id"/> <column name="created_at"/> </table> <table name="table2"> <column name="id"/> <column name="updated_at"/> </table> </database> I want to be able to test using an xsl:key if specific table has a specific column by name. For instance, I want to know if a table has a 'created_at' column so I can write specific code within the transformation. I've gotten a general key that will test if any table has a given column by name, but have not figured out how to make it specific to the table the transformation is currently working with. <xsl:key name="columnTest" match="column" use="@name"/> <xsl:for-each select="database/table"> <xsl:choose> <xsl:when test="key('columnTest', 'created_at')"> <xsl:text>true</xsl:text> </xsl:when> <xsl:otherwise> <xsl:text>false</xsl:text> </xsl:otherwise> </xsl:choose> </xsl:for-each> So I end up with 'true' for all the tables. Any guidance would be appreciated.

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• django + south + python: strange behavior when using a text string received as a parameter in a func

  - by carlosescri

  Hello, this is my first question. I'm trying to execute a SQL query in django (south migration): from django.db import connection # ... class Migration(SchemaMigration): # ... def transform_id_to_pk(self, table): try: db.delete_primary_key(table) except: pass finally: cursor = connection.cursor() # This does not work cursor.execute('SELECT MAX("id") FROM "%s"', [table]) # I don't know if this works. try: minvalue = cursor.fetchone()[0] except: minvalue = 1 seq_name = table + '_id_seq' db.execute('CREATE SEQUENCE "%s" START WITH %s OWNED BY "%s"."id"', [seq_name, minvalue, table]) db.execute('ALTER TABLE "%s" ALTER COLUMN id SET DEFAULT nextval("%s")', [table, seq_name + '::regclass']) db.create_primary_key(table, ['id']) # ... I use this function like this: self.transform_id_to_pk('my_table_name') So it should: Find the biggest existent ID or 0 (it crashes) Create a sequence name Create the sequence Update the ID field to use sequence Update the ID as PK But it crashes and the error says: File "../apps/accounting/migrations/0003_setup_tables.py", line 45, in forwards self.delegation_table_setup(orm) File "../apps/accounting/migrations/0003_setup_tables.py", line 478, in delegation_table_setup self.transform_id_to_pk('accounting_delegation') File "../apps/accounting/migrations/0003_setup_tables.py", line 20, in transform_id_to_pk cursor.execute(u'SELECT MAX("id") FROM "%s"', [table.encode('utf-8')]) File "/Library/Python/2.6/site-packages/django/db/backends/util.py", line 19, in execute return self.cursor.execute(sql, params) psycopg2.ProgrammingError: relation "E'accounting_delegation'" does not exist LINE 1: SELECT MAX("id") FROM "E'accounting_delegation'" ^ I have shortened the file paths for convenience. What does that "E'accounting_delegation'" mean? How could I get rid of it? Thank you! Carlos.

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• Is there an ORM that supports composition w/o Joins

  - by Ken Downs

  EDIT: Changed title from "inheritance" to "composition". Left body of question unchanged. I'm curious if there is an ORM tool that supports inheritance w/o creating separate tables that have to be joined. Simple example. Assume a table of customers, with a Bill-to address, and a table of vendors, with a remit-to address. Keep it simple and assume one address each, not a child table of addresses for each. These addresses will have a handful of values in common: address 1, address 2, city, state/province, postal code. So let's say I'd have a class "addressBlock" and I want the customers and vendors to inherit from this class, and possibly from other classes. But I do not want separate tables that have to be joined, I want the columns in the customer and vendor tables respectively. Is there an ORM that supports this? The closest question I have found on StackOverflow that might be the same question is linked below, but I can't quite figure if the OP is asking what I am asking. He seems to be asking about foregoing inheritance precisely because there will be multiple tables. I'm looking for the case where you can use inheritance w/o generating the multiple tables. Model inheritance approach with Django's ORM

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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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• How can I optimize retrieving lowest edit distance from a large table in SQL?

  - by Matt

  Hey, I'm having troubles optimizing this Levenshtein Distance calculation I'm doing. I need to do the following: Get the record with the minimum distance for the source string as well as a trimmed version of the source string Pick the record with the minimum distance If the min distances are equal (original vs trimmed), choose the trimmed one with the lowest distance If there are still multiple records that fall under the above two categories, pick the one with the highest frequency Here's my working version: DECLARE @Results TABLE ( ID int, [Name] nvarchar(200), Distance int, Frequency int, Trimmed bit ) INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@Source, [Name])) As Distance, Frequency, 'False' As Trimmed FROM MyTable INSERT INTO @Results SELECT ID, [Name], (dbo.Levenshtein(@SourceTrimmed, [Name])) As Distance, Frequency, 'True' As Trimmed FROM MyTable SET @ResultID = (SELECT TOP 1 ID FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @Result = (SELECT TOP 1 [Name] FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultDist = (SELECT TOP 1 Distance FROM @Results ORDER BY Distance, Trimmed, Frequency) SET @ResultTrimmed = (SELECT TOP 1 Trimmed FROM @Results ORDER BY Distance, Trimmed, Frequency) I believe what I need to do here is to.. Not dumb the results to a temporary table Do only 1 select from `MyTable` Setting the results right in the select from the initial select statement. (Since select will set variables and you can set multiple variables in one select statement) I know there has to be a good implementation to this but I can't figure it out... this is as far as I got: SELECT top 1 @ResultID = ID, @Result = [Name], (dbo.Levenshtein(@Source, [Name])) As distOrig, (dbo.Levenshtein(@SourceTrimmed, [Name])) As distTrimmed, Frequency FROM MyTable WHERE /* ... yeah I'm lost */ ORDER BY distOrig, distTrimmed, Frequency Any ideas?

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• How do I build a class that shares a table with multiple columns in MVC3?

  - by Barrett Kuethen

  I have a Job table public class Job { public int JobId { get; set; } public int SalesManagerId { get; set; } public int SalesRepId { get; set; } } and a Person table public class Person { public int PersonId { get; set; } public int FirstName { get; set; } public int LastName { get; set; } } My question is, how do I link the SalesManagerId to the Person (or PersonId) as well as the SalesRepId to the Person (PersonId)? The Sales Manager and Sales Rep are independent of each other. I just don't want to make 2 different lists to support the Sales Manager and Sales Rep roles. I'm new to MVC3, but it seems public virtual Person Person {get; set; } would be the way to go, but that doesn't work. Any help would be appreciated! Thanks!

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• Why isn't the Cache invalidated after table update using the SqlCacheDependency?

  - by Jason

  I have been trying to get SqlCacheDependency working. I think I have everything set up correctly, but when I update the table, the item in the Cache isn't invalidated. Can you look at my code and see if I am missing anything? I enabled the Service Broker for the Sandbox database. I have placed the following code in the Global.asax file. I also restart IIS to make sure it is called. void Application_Start(object sender, EventArgs e) { SqlDependency.Start(ConfigurationManager.ConnectionStrings["SandboxConnectionString"].ConnectionString); } I have placed this entry in the web.config file: <system.web> <caching> <sqlCacheDependency enabled="true" pollTime="10000"> <databases> <add name="Sandbox" connectionStringName="SandboxConnectionString"/> </databases> </sqlCacheDependency> </caching> </system.web> I call this code to put the item into the cache: protected void CacheDataSetButton_Click(object sender, EventArgs e) { using (SqlConnection sqlConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["SandboxConnectionString"].ConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand("SELECT PetID, Name, Breed, Age, Sex, Fixed, Microchipped FROM dbo.Pets", sqlConnection)) { using (SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(sqlCommand)) { DataSet petsDataSet = new DataSet(); sqlDataAdapter.Fill(petsDataSet, "Pets"); SqlCacheDependency petsSqlCacheDependency = new SqlCacheDependency(sqlCommand); Cache.Insert("Pets", petsDataSet, petsSqlCacheDependency, DateTime.Now.AddSeconds(10), Cache.NoSlidingExpiration); } } } } Then I bind the GridView with this code: protected void BindGridViewButton_Click(object sender, EventArgs e) { if (Cache["Pets"] != null) { GridView1.DataSource = Cache["Pets"] as DataSet; GridView1.DataBind(); } } Between attempts to DataBind the GridView, I change the table's values expecting it to invalidate the Cache["Pets"] item, but it seems to stay in the Cache indefinitely.

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• How to change the css class="current" when using page jumping (single page website)?

  - by Bryan

  Morning, I must be asking google all the wrong questions, because I can't find anything similar. I have a standard navigation list, but I'm using page jumping because I wanted a single web page. <ul> <li><a href="#livestream">Livestream</a></li> <li><a href="#media">Media</a></li> <li><a href="#crew">Crew</a></li> <li><a href="#services">Services</a></li> <li><a href="#contact">Contact</a></li> </ul> But I can't for the life of me figure out how to make the class="current" when using page jumping. I've tried this bit of jquery because it appears to be what I'm looking for, but it did nothing. I don't think it'll work for #links. Any ideas?

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• Ways to update a dependent table in the same MySQL transaction?

  - by codie

  I need to update two tables inside a single transaction. The individual queries look something like this: 1. INSERT INTO t1 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = val2; If the above query causes an insert then I need to run the following statement on the second table: 2. INSERT INTO t2 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = col2 + val2; otherwise, 3. UPDATE t2 SET col2 = col2 - old_val2 + val2 WHERE col1 = val1; -- old_val2 is the value of t1.col2 before it was updated Right now I run a SELECT on t1 first, to determine whether statement 1 will cause an insert or update on t1. Then I run statement 1 and either of 2 and 3 inside a transaction. What are the ways in which I can do all of these inside one transaction itself? The approach I was thinking of is the following: UPDATE t2, t1 set t2.col2 = t2.col2 - t1.col2 WHERE t1.col1 = t2.col2 and t1.col1 = val1; INSERT INTO t1 (col1, col2) VALUES (val1, val2) ON DUPLICATE KEY UPDATE col2 = val2; INSERT INTO t2, t1 (t2.col1, t2.col2) VALUES (t1.col1, t1.col2) ON DUPLICATE KEY UPDATE t2.col2 = t2.col2 + t1.col2 WHERE t1.col1 = t2.col2 and t1.col1 = val1; Unfortunately, there's no multi-table INSERT... ON DUPLICATE KEY UPDATE in MySQL 5.0. What else could I do?

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• How can you push a new view with a grouped table?

  - by Tanner

  Hi All, Ive been trying to push a new view when a cell is tapped but absolutely nothing happens. I figured grouped style pushed the same as plain. Here is my code: -(void)viewDidLoad { [super viewDidLoad]; contactArray = [[NSArray alloc] initWithObjects:@"iPhone",@"iPod",@"MacBook",@"MacBook Pro",nil]; shareArray = [[NSArray alloc] initWithObjects:@"Flex",@"AIR",@"PhotoShop",@"Flash",nil]; } -(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 2; } // Customize the number of rows in the table view. -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { if(section == 0) return [contactArray count]; else return [shareArray count]; } -(NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section{ if(section == 0){ return @"Contact"; }else{ return @"Share"; } } -(NSString *)tableView:(UITableView *)tableView titleForFooterInSection:(NSInteger)section{ if(section == 0){ return @"Footer for Apple Products"; }else{ return @"Footer for Adobe Softwares"; } } // Customize the appearance of table view cells. -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease]; } // Set up the cell... if(indexPath.section == 0){ cell.text = [contactArray objectAtIndex:indexPath.row]; }else{ cell.text = [shareArray objectAtIndex:indexPath.row]; } return cell; } -(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { //NextViewController *nextController = [[NextViewController alloc] initWithNibName:@"NextView" bundle:nil]; //[self.navigationController pushViewController:nextController animated:YES]; if([contactArray objectAtIndex:indexPath.row] == @"iPhone"){ LandscapeHydrogen *abo = [[LandscapeHydrogen alloc] initWithNibName:@"LandscapeHydrogen" bundle:nil]; [self.navigationController pushViewController:abo animated:NO]; [abo release]; } } Any help is appreciated.

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• How would I find all sets of N single-digit, non-repeating numbers that add up to a given sum in PHP

  - by TerranRich

  Let's say I want to find all sets of 5 single-digit, non-repeating numbers that add up to 30... I'd end up with [9,8,7,5,1], [9,8,7,4,2], [9,8,6,4,3], [9,8,6,5,2], [9,7,6,5,3], and [8,7,6,5,4]. Each of those sets contains 5 non-repeating digits that add up to 30, the given sum. Any help would be greatly appreciated. Even just a starting point for me to use would be awesome. I came up with one method, which seems like a long way of going about it: get all unique 5-digit numbers (12345, 12346, 12347, etc.), add up the digits, and see if it equals the given sum (e.g. 30). If it does, add it to the list of possible matching sets. I'm doing this for a personal project, which will help me in solving Kakuro puzzles without actually solving the whole thing at once. Yeah, it may be cheating, but it's... it's not THAT bad... :P

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• How to cope with null results in SQL Tasks that return single rows in SSIS 2005?

  - by JSacksteder

  In a dataflow task, I can slip a rowcount into the processing flow and place the count into a variable. I can later use that variable to conditionally perform some other work if the rowcount was 0. This works well for me, but I have no corresponding strategy for sql tasks expected to return a single row. In that event, I'm returning those values into variables. If the lookup produces no rows, the sql task fails when assigning values into those variables. I can branch on that component failing, but there's a side effect of that - if I'm running the job as a SQL server agent job step, the step returns DTSER_FAILURE, causing the step to fail. I can tell the sql agent to disregard the step failure, but then I won't know if I have a legitimate error in that step. This seems harder than it should be. The only strategy I can think of is to run the same query with a count(*) aggregate and test if that returns a number 0 and if so running the query again without the count. That's ugly because I have the same query in two places that I need to keep in sync. Is there a better way?

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• Fetch Data using predicate. Retrieve single value.

  - by Mr. McPepperNuts

  XYZAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate]; NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext; NSFetchRequest *request = [[NSFetchRequest alloc] init]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == %@", entryToSearchFor]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Entry" inManagedObjectContext:managedObjectContext]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [request setEntity: entity]; [request setPredicate: predicate]; NSArray *results = [managedObjectContext executeFetchRequest:request error:nil]; if (results == nil) { NSLog(@"No results found"); }else { NSLog(@"entryToSearchFor %@", entryToSearchFor); NSLog(@"results %@", [results objectAtIndex:0]); } I want to retrieve a single value (String) from "Entry." I believe I must be missing. Can someone point it out? Btw, the NSLog results outputs the following: results <NSManagedObject: 0x3d2d360> (entity: Entry; id: 0x3d13650 <x-coredata://6EA12ADA-8C0B-477F-801C-B44FE6E6C91C/Entry/p3> ; data: <fault>)

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• Java - How to declare table[i][j] elements as instance variables?

  - by JDelage

  All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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• JSP/Struts2/Hibernate: loop through a self-referencing table.

  - by TBW

  Hello everyone, Let's say we have a self-referencing table called PERSON, with the following columns: ID, PARENT, where PARENT is a foreign key to the ID column of another element in the PERSON table. Of course, many persons can have the same parent. I use Hibernate 3 in lazy fetching mode to deal with the database. Hibernate fetches a person element from the database, which is then put in the ValueStack by the Struts2 action, to be used on the result JSP page. Now the question is : In JSP, how can I do to display all the child (and the child's child, and so on, like a family tree) of this person element? Of course, for the n+1 children I can use the < s:iterator tag over the person.person. I can also nest another < s:iterator tag over person.person.person to get the n+2 children. But what if I want to do this in an automated manner, up to the last n+p child, displaying in the process all the children of all the n+1..n+p elements? I hope I have been clear enough. Thank you all for your time. -- TBW.

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• What is an efficient strategy for multiple threads posting jobs and waiting for response from a single thread?

  - by jakewins

  In java, what is an efficient solution to the following problem: I have multiple threads (10-20 or so) generating jobs ("Job Creators"), and a single thread capable of performing them ("The worker"). Once a job creator has posted a job, it should wait for the job to finish, yielding no result other than "it's done", before it keeps going. For sending the jobs to the worker thread, I think a ring buffer or similar standard fan-in setup would perhaps be a good approach? But for a Job Creator to find out that her job has been done, I'm not so sure.. The job creators could sleep, and the worker interrupt them when done.. Or each job creator could have an atomic boolean that it checks, and that the worker sets. I dunno, neither of those feel very nice. I'd like to do it with as few (none, if possible) locks as absolutely possible. So to be clear: What I'm looking for is speed, not necessarily simplicity. Does anyone have any suggestions? Links to reading about concurrency strategies would also be very welcome!

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• PHP Doxygen Collaboration Diagrams

  - by Shabbyrobe

  I've started playing around with doxygen to generate documentation from my PHP code. I notice there are two diagrams in the generated output - inheritance and collaboration. I know about the inheritance one, but the collaboration one has piqued my interest since reading the manual: If the COLLABORATION_GRAPH and HAVE_DOT tags are set to YES then doxygen will generate a graph for each documented class showing the direct and indirect implementation dependencies (inheritance, containment, and class references variables) of the class with other documented classes. The impression I get from that description is that composition relationships should be represented by the collaboration diagram as well, but it always seems to just be identical to the inheritance one. Is there something I can do to hint to Doxygen the things I would like to appear in this diagram? Does it just not work with PHP?

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• SQL Server CE rollback does not undo delete.

  - by INTPnerd

  I am using SQL Server CE 3.5 and C# with the .NET Compact Framework 3.5. In my code I am inserting a row, then starting a transaction, then deleting that row from a table, and then doing a rollback on that transaction. But this does not undo the deletion. Why not? Here is my code: SqlCeConnection conn = ConnectionSingleton.Instance; conn.Open(); UsersTable table = new UsersTable(); table.DeleteAll(); MessageBox.Show("user count in beginning after delete: " + table.CountAll()); table.Insert( new User(){Id = 0, IsManager = true, Pwd = "1234", Username = "Me"}); MessageBox.Show("user count after insert: " + table.CountAll()); SqlCeTransaction transaction = conn.BeginTransaction(); table.DeleteAll(); transaction.Rollback(); transaction.Dispose(); MessageBox.Show("user count after rollback delete all: " + table.CountAll()); The messages indicate that everything works as expected until the very end where the table has a count of 0 indicating the rollback did not undo the deletion.

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