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  • C#: Preferred pattern for functions requiring arguments that implement two interfaces

    - by JS Bangs
    The argument to my function f() must implement two different interfaces that are not related to each other by inheritance, IFoo and IBar. I know of two different ways of doing this. The first is to declare an empty interface that inherits from both: public interface IFooBar : IFoo, IBar { // nothing to see here } public int f(IFooBar arg) { // etc. } This, of course, requires that the classes declare themselves as implementing IFooBar rather than IFoo and IBar separately. The second way is to make f() generic with a constraint: public int f<T>(T arg) where T : IFoo, IBar { // etc. } Which of these do you prefer, and why? Are there any non-obvious advantages or disadvantages to each?

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  • Saving related model objects

    - by iHeartDucks
    I have two related models (one to many) in my django app and When I do something like this ObjBlog = Blog() objBlog.name = 'test blog' objEntry1 = Entry() objEntry1.title = 'Entry one' objEntry2 = Entry() objEntry2.title = 'Entry Two' objBlog.entry_set.add(objEntry1) objBlog.entry_set.add(objEntry2) I get an error which says "null value in column and it violates the foreign key not null constraint". None of my model objects have been saved. Do I have to save the "objBlog" before I could set the entries? I was hoping I could call the save method on objBlog to save it all. NOTE: I am not creating a blog engine and this is just an example.

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  • Should we use a CSS frame work ? Are they worth it ?

    - by Gaurav M
    CSS frameworks have nice styles inbuilt and ask you to focuses on the grids but still there is a bit of dependency and lack of freedom it provide.. If I need to generate a webpage by looking on a PSD based mockup screen ..either i will use the classes provided by the framework but if that actual measurements does not exist I need to again specify my own rules that will add upto my CSS filesize and if performance is a constraint as always it is...you need not a big size file..though its in kb but every drop counts. Any comments and suggestions to use the framework in a best possible way.

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  • How to specify a different column for a @Inheritance JPA annotation

    - by Cue
    @Entity @Inheritance(strategy = InheritanceType.JOINED) public class Foo @Entity @Inheritance(strategy = InheritanceType.JOINED) public class BarFoo extends Foo mysql> desc foo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ mysql> desc barfoo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | | foo_id | int | | bar_id | int | +---------------+-------------+ mysql> desc bar; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ Is it possible to specify column barfo.foo_id as the joined column? Are you allowed to specify barfoo.id as BarFoo's @Id since you are overriding the getter/seeter of class Foo? I understand the schematics behind this relationship (or at least I think I do) and I'm ok with them. The reason I want an explicit id field for BarFoo is exactly because I want to avoid using a joined key (foo _id, bar _id) when querying for BarFoo(s) or when used in a "stronger" constraint. (as Ruben put it)

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  • Is it a good idea to use a computed column as part of a primary key ?

    - by Brann
    I've got a table defined as : OrderID bigint NOT NULL, IDA varchar(50) NULL, IDB bigint NULL, [ ... 50 other non relevant columns ...] The natural primary key for this table would be (OrderID,IDA,IDB), but this it not possible because IDA and IDB can be null (they can both be null, but they are never both defined at the same time). Right now I've got a unique constraint on those 3 columns. Now, the thing is I need a primary key to enable transactional replication, and I'm faced with two choices : Create an identity column and use it as a primary key Create a non-null computed column C containing either IDA or IDB or '' if both columns were null, and use (OrderID,C) as my primary key. The second alternative seams cleaner as my PK would be meaningful, and is feasible (see msdn link), but since I've never seen this done anywhere, I was wondering if they were some cons to this approach.

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  • One to One relationship in MySQL

    - by Botto
    I'm trying to make a one to one relationship in a MySQL DB. I'm using the InnoDB engine and the basic table looks like this: CREATE TABLE `foo` ( `fooID` INT(11) NOT NULL PRIMARY KEY AUTO_INCREMENT, `name` TEXT NOT NULL ) CREATE TABLE `bar` ( `barName` VARCHAR(100) NOT NULL, `fooID` INT(11) NOT NULL PRIMARY KEY, CONSTRAINT `contact` FOREIGN KEY (`fooID`) REFERENCES `foo`(`fooID`) ) Now once I have set up these I alter the foo table so that the fooID also becomes a foreign key to the fooID in bar. The only issue I am facing with this is that there will be a integrity issue when I try to insert into either. I would like some help, thanks.

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  • Copying Data between table without identity column

    - by user668479
    I have two table and I need to copy the data across from SRCServiceUsers to Clients Everytime i run it I get the following: Violation of PRIMARY KEY constraint 'PK_Clients'. Cannot insert duplicate key in object 'dbo.Clients'. The statement has been terminated. The Primary key ClientId field is not an identity column and therefore requires filling To date I have the following insert into Clients( ClientID, Title, Forenames, FamilyName, [Address], Town, County, PostCode, PhoneNumber, StartDate) SELECT ( Select Max(Clients.ClientID)+ 1, SRCServiceUsers.Title, SRCServiceUsers.[First Names], SRCServiceUsers.Surname, --BUILD UP MUITIPLE COLUMNS SRCServiceUsers.[Property Name] + ', ' + SRCServiceUsers.Street + ', ' + SRCServiceUsers.Suburb as [Address], SRCServiceUsers.Town, SRCServiceUsers.County, SRCServiceUsers.Postcode, SRCServiceUsers.Telephone, SRCServiceUsers.[Start Date] From srcsERVICEuSERS How can i autoincrement the PK field - CLientID when inserting the data? Many thanks Andrew

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  • SubSonic isn't generating MySql foreign key tables

    - by keith
    I two tables within a MySql 5.1.34 database. When using SubSonic to generate the DAL, the foreign-key relationship doesn't get scripted, ie; I have no Parent.ChildCollection object. Looking inside the generated DAL Parent class shows the following; //no foreign key tables defined (0) I have tried SubSonic 2.1 and 2.2, and various MySql 5 versions. I must be doing something wrong procedurally - any help would be greatly appreciated. This has always just worked 'out-the-box' when using MS-SQL. TABLE `parent` ( `ParentId` INT(11) NOT NULL AUTO_INCREMENT, `SomeData` VARCHAR(25) DEFAULT NULL, PRIMARY KEY (`ParentId`) ) ENGINE=INNODB DEFAULT CHARSET=latin1; TABLE `child` ( `ChildId` INT(11) NOT NULL AUTO_INCREMENT, `ParentId` INT(11) NOT NULL, `SomeData` VARCHAR(25) DEFAULT NULL, PRIMARY KEY (`ChildId`), KEY `FK_child` (`ParentId`), CONSTRAINT `FK_child` FOREIGN KEY (`ParentId`) REFERENCES `parent` (`ParentId`) ) ENGINE=INNODB DEFAULT CHARSET=latin1;

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  • How to persist non-trivial fields in Play Framework

    - by AlexR
    I am trying to persist complex objects using Ebeans in Play Framework (2.03). In particular, I've created a class that contains a field of type weka.classifier.Classifier (Weka is a popular machine learning library - see http://weka.sourceforge.net/doc/weka/classifiers/Classifier.html). Classifier implements Serializeable so I hoped that I can get away with something like @Entity @Table(name = "classifiers") public class ClassifierData extends Model { @Id public Long id; public Classifier classifier; } However, the Evolutions script suggests the following database structure: create table classifiers ( id bigint auto_increment not null, constraint pk_classifiers primary key (id)) ) In other words, it ignores the field of type Classifier. (The database is MySQL if it makes any difference) What should I do to store complex serializeable objects using Ebean/Evolutions/PlayFramework?

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  • DB2 Child Table - Auto Delete With Parent

    - by gamerzfuse
    I have a bit of a task before me. (DB2 Database) I need to create a table that will be a child table (is that what it is called in SQL?) I need it so that it has a foreign key constraint with my other table, so when the parent table is modified (record deleted) the child table also loses that record. Once I have the table, I also need to populate it with the data from the other table (if there is an easy way to UPDATE this). If you could point me in the right direction, this would help alot, as I do not even know what syntax to look for. Thanks in advance

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  • Grails unit testing domain classes with Set properties - is this safe?

    - by Ali G
    I've created a domain class in Grails like this: class MyObject { static hasMany = [tags: String] // Have to declare this here, as nullable constraint does not seem to be honoured Set tags = new HashSet() static constraints = { tags(nullable: false) } } Writing unit tests to check the size and content of the MyObject.tags property, I found I had to do the following: assertLength(x, myObject.tags as Object[]) assertEquals(new HashSet([...]), myObject.tags) To make the syntax nicer for writing the tests, I implemented the following methods: void assertEquals(List expected, Set actual) { assertEquals(new HashSet(expected), actual) } void assertLength(int expected, Set set) { assertLength(expected, set as Object[]) } I can now call the assertLength() and assertEquals() methods directly on an instance of Set, e.g. assertLength(x, myObject.tags) assertEquals([...], myObject.tags) I'm new to Groovy and Grails, so unaware how dangerous method overloading like this is. Is it safe? If so, I'm slightly* surprised that these methods (or similar) aren't already available - please let me know if they are. * I can see how these methods could also introduce ambiguity if people weren't expecting them. E.g. assertLength(1, set) always passes, no matter what the content of set

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  • mysql foreign key problem.

    - by JP19
    Hi, What is wrong with the foreign key addition here: mysql> create table notes ( id int (11) NOT NULL auto_increment PRIMARY KEY, note_type_id smallint(5) NOT NULL, data TEXT NOT NULL, created_date datetime NOT NULL, modified_date timestamp NOT NULL on update now()) Engine=InnoDB; Query OK, 0 rows affected (0.08 sec) mysql> create table notetypes ( id smallint (5) NOT NULL auto_increment PRIMARY KEY, type varchar(255) NOT NULL UNIQUE) Engine=InnoDB; Query OK, 0 rows affected (0.00 sec) mysql> alter table `notes` add constraint foreign key(`note_type_id`) references `notetypes`.`id` on update cascade on delete restrict; ERROR 1005 (HY000): Can't create table './admin/#sql-43e_b762.frm' (errno: 150) Thanks JP

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  • some examples for using specific searchalgorithm

    - by Robert
    I could understand the following search algorithms: Constraint Satisfaction with Arc Consistency, Uninformed search A* Search MinMax I would understand the definition and working principles of the above algorithm,but could you please give me some real world examples that the above algorithms will be suitable?My idea would be: For CSP with Arc Consistency,assign students to groups that each group must contain both technical and management students,and no 2 technical students in a same group. Uniformed Search: search for a file under UNIX directoy. A* Search: search a way (staring from home) to go to mulitple stores to buy things then get back home with minimum total travelling time. MinMax:Go or other Chess. Please correct me if I am wrong.

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  • Does SQL Server 2005 error message numbers back to the asp.net application?

    - by Duke
    I'd like to get the message number and severity level information from SQL Server upon execution of an erroneous query. For example, when a user attempts to delete a row being referenced by another record, and the cascade relationship is "no action", I'd like the application to be able to check for error message 547 ("The DELETE statement conflicted with the REFERENCE constraint...") and return a user friendly and localized message to the user. When running such a query directly on SQL Server, the following message is printed: Msg 547, Level 16, State 0, Line 1 <Error message...> In an Asp.Net app is this information available in an event handler parameter or elsewhere? Also, I don't suppose anyone knows where I can find a definitive reference of SQL Server message numbers?

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  • SSRS mysterious extra pages

    I have two reports that are setup with the same page dimensions- A4 portrait, with page margins of 1cm. When I run the reports seperately and print them they both come out as expected: fitting into the width constraint of the page. However, when I include one report as a subreport in the other and then run and print the "master" report I start to experience problems. Even though both reports appear I get extra blank pages appearing every other page in the output. I'm sure I'm missing a simple trick - probably with the page sizes of the two reports but I can't figure it out - any pointers? I don't mind changing the setup of the subreport as it will never be run as a seperate eport in the wild, I only included that step to prove that it did indeed fit within the page!

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  • C# Generics Casting

    - by Nippysaurus
    Visual sutdio 2008 has the ability to automatically create unit test stubs. I have used this to create some basic unit tests, but I am confused by something: private class bla : BaseStoreItem { // } /// <summary> ///A test for StoreData ///</summary> public void StoreDataTestHelper<T>() where T : BaseStoreItem { FileStore<T> target = new FileStore<T>(); // TODO: Initialize to an appropriate value BaseStoreItem data = new bla(); target.StoreData(data); } [TestMethod()] public void StoreDataTest() { //Assert.Inconclusive("No appropriate type parameter is found to satisfies the type constraint(s) of T. " + // "Please call StoreDataTestHelper<T>() with appropriate type parameters."); StoreDataTestHelper<bla>(); } Why do I get "Error: Cannot convert type 'StorageUnitTests.FileStoreTest.bla' to 'T'" when T is type "bla"? I know "bla" is not a good function name, but its just an example.

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  • Social Network directed Graph Library? .NET

    - by MRFerocius
    Hello everybody, I am on a project where I have multiple users of a portal and they are connected to other users of the portal, now we are asked to draw a "Social Network" relationship graph to see the relationships. The constraint is that this graph has to be seen on the WEB BROWSER. The graph has to be something like: Is there any C# library or component to draw this type of graphs? We have already checked these: http://flare.prefuse.org/ http://www.yworks.com/en/products_yfiles_practicalinfo_gallery.html .NET graph library around? http://quickgraph.codeplex.com/ https://graphsharp.codeplex.com/ http://research.microsoft.com/en-us/downloads/f1303e46-965f-401a-87c3-34e1331d32c5/default.aspx http://sourceforge.net/projects/zedgraph/ But I want to check if you already used some other and your feedback... Thanks in advanced!

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  • discovering files in the FileSystem, through SSIS

    - by cometbill
    I have a folder where files are going to be dropped for importing into my data warehouse. \\server\share\loading_area I have the following (inherited) code that uses xp_cmdshell shivers to call out to the command shell to run the DIR command and insert the resulting filenames into a table in SQL Server. I would like to 'go native' and reproduce this functionality in SSIS. Thanks in advance guys and girls. Here's the code USE MyDatabase GO declare @CMD varchar(500) declare @EXTRACT_PATH varchar(255) set @EXTRACT_PATH = '\\server\share\folder\' create table tmp_FILELIST([FILENUM] int identity(1,1), [FNAME] varchar(100), [FILE_STATUS] varchar(20) NULL CONSTRAINT [DF_FILELIST_FILE_STATUS] DEFAULT ('PENDING')) set @CMD = 'dir ' + @EXTRACT_PATH + '*.* /b /on' insert tmp_FILELIST([FNAME]) exec master..xp_cmdshell @CMD --remove the DOS reply when the folder is empty delete tmp_FILELIST where [FNAME] is null or [FNAME] = 'File Not Found' --Remove my administrative and default/common, files not for importing, such as readme.txt delete tmp_FILELIST where [FNAME] is null or [FNAME] = 'readme.txt'

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  • how to use use case relations - uml

    - by joao alves
    Heys guys! Im have been study UML and im trying to to design the use case diagram of a problem. Lets supose my app consists in this: Two Requesites: - create teams - create players This is the deal: A user can create a team, and after create a team he can create players for that team(not required). But in this app there are multiple users, and a user can create a team and other user can create players. The only constraint is that to create players must exist alreay a team. I research and i end up a little confuse. If i get the concepts of relations on use case diagrams right, i think i should have the folowwing two use cases: [use case - create team] <-------extends---- [use case - create player] I need opinions,Is this the proper solution? or should i have two not related use cases? Thanks in advance, and im sorry my english.

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  • How could I do something like this in a XML schema?

    - by chobo2
    Hi I want to mass create some users and I want to set the users timezone automatically. However I am using timezones generated by this Dictionary<string, TimeZoneInfo> storeZoneName = TimeZoneInfo.GetSystemTimeZones().ToDictionary(z => z.DisplayName); So I need the names to be exactly like the ones this list returns. So can I put like a constraint on that xml node that the name has to exactly match one of the names. So I am guessing I will need to write this list somewhere in the file and that's what I am not sure if you can do something like that in a schema.

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  • In C#: How to declare a generic Dictionary with a type as key and an enumeration of that type as val

    - by Marcel
    Hi all, I want to declare a dictionary that stores typed IEnumerable's of a specific type, with that exact type as key, like so: (Edited to follow johny g's comment) private IDictionary<Type, IEnumerable<T>> _dataOfType where T: BaseClass; //does not compile! The concrete classes I want to store, all derive from BaseClass, therefore the idea to use it as constraint. The compiler complains that it expects a semicolon after the member name. If it would work, I would expect this would make the later retrieval from the dictionary simple like: IEnumerable<ConcreteData> concreteData; _sitesOfType.TryGetValue(typeof(ConcreteType), out concreteData); How to define such a dictionary?

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  • Haskell: Defaulting constraints to type

    - by yairchu
    Consider this example: applyKTimes :: Integral i => i -> (a -> a) -> a -> a applyKTimes 0 _ x = x applyKTimes k f x = applyKTimes (k-1) f (f x) applyThrice :: (a -> a) -> a -> a applyThrice = applyKTimes 3 The 3 in applyThrice is defaulted by GHC to an Integer as shown when compiling with -Wall: Warning: Defaulting the following constraint(s) to type 'Integer' 'Integral t' arising from a use of 'applyKTimes' So I guess that Integer is the default Integral a => a. Is there a way to define "default types" for other constraints too? Is using default types bad practice? (it does complain when using -Wall..)

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  • How to solve 'Badly constructed integrity constraints' in doctrine

    - by Carson
    When I execute the command './doctrine build-all-reload' It comes out the following output: build-all-reload - Are you sure you wish to drop your databases? (y/n) y build-all-reload - Successfully dropped database for connection named 'doctrine' build-all-reload - Generated models successfully from YAML schema build-all-reload - Successfully created database for connection named 'doctrine' Badly constructed integrity constraints. Cannot define constraint of different f ields in the same table. Here is the source code of Doctrine that outputs the error: here What causes the error? How can I debug where the error comes from?

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  • PL/SQL exception and Java programs

    - by edwards
    Hi Business logic is coded in pl/sql packages procedures and functions. Java programs call pl/sql packages procedures and functions to do database work. pl/sql programs store exceptions into Oracle tables whenever an exception is raised. How would my java programs get the exceptions since the exception instead of being propagated from pl/sql to java is getting persisted to a oracle table and the procs/functions just return 1 or 0. Sorry folks i should have added this constraint much earlier and avoided this confusion. As with many legacy projects we don't have the freedom to modify the stored procedures.

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  • How do I drop a foerign key in mssql?

    - by mmattax
    I have created a foreign key (in mssql / tsql) by: alter table company add CountryID varchar(3); alter table company add constraint Company_CountryID_FK foreign key(CountryID) references Country; I then run this query: alter table company drop column CountryID; and I get this error: Msg 5074, Level 16, State 4, Line 2 The object 'Company_CountryID_FK' is dependent on column 'CountryID'. Msg 4922, Level 16, State 9, Line 2 ALTER TABLE DROP COLUMN CountryID failed because one or more objects access this column. I have tried this, yet it does not seem to work: alter table company drop foreign key Company_CountryID_FK; alter table company drop column CountryID; What do I need to do to drop the CountryID column? Thanks.

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