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• Multiple column foreign key contraints

  - by eugene4968

  I want to setup table constraints for the following scenario and I’m not sure how to do it or if it’s even possible in SQL Server 2005. I have three tables A,B,C. C is a child of B. B will have a optional foreign key(may be null) referencing A. For performance reasons I also want table C to have the same foreign key reference to table A. The constraint on table C should be that C must reference its parent (B) and also have the same foreign key reference to A as its parent. Anyone have any thoughts on how to do this?

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• Change master table PK and update related table FK (changing PK from Autoincrement to UUID on Mysql)

  - by eleonzx

  I have two related tables: Groups and Clients. Clients belongs to Groups so I have a foreign key "group_id" that references the group a client belongs to. I'm changing the Group id from an autoincrement to a UUID. So what I need is to generate a UUID for each Group and update the Clients table at once to reflect the changes and keep the records related. Is there a way to do this with multiple-table update on MySQL? Adding tables definitions for clarification. CREATE TABLE `groups` ( `id` char(36) NOT NULL, `name` varchar(255) DEFAULT NULL, `created` datetime DEFAULT NULL, `modified` datetime DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ CREATE TABLE `clients` ( `id` char(36) NOT NULL, `name` varchar(255) NOT NULL, `group_id` char(36) DEFAULT NULL, `active` tinyint(1) DEFAULT '1' PRIMARY KEY (`id`), KEY `fkgp` (`group_id`), CONSTRAINT `fkgp` FOREIGN KEY (`group_id`) REFERENCES `groups` (`id`) ON DELETE NO ACTION ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$

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• How to call javascript function when url variable is sent

  - by mattlarkin

  Hello, heres basically what I need to get done. I have a jsp page which allows me to add/modify/delete an item. The items are stored in a database which I have controller classes to access(dont worry bout that part) When an item gets selected and deleted the id of the item gets sent to the controller to be processed. The item will not always be deleted if their is a foreign key constraint so I send either a delete=true or delete=false through url back to the jsp page. I would like to have it so a javascript function gets called displaying an alert saying the item was deleted or the item was not deleted. can someone please tell me the best way to do this? thank you

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• receive a responseText in ajax but without div tag

  - by kawtousse

  Hi everyone I want to know if there is any other way whithout using a div tag to receive response html when sending parameter whith ajax. I'am asking because when iam building the select in other servlet and returning the result to jsp it receive the responsehtml in a div tag when we use the famous: x = xhr.responseText; document.getElementById('param').innerHTML = x; with param is the id of div tag. Note: this works fine when populating ddl but its constraint are multiple for my case. Thinks.

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• Typeclass instances for unnamed types in Scala

  - by ncreep

  How would one encode the following constraint in Scala (pseudocode)? def foo(x: T forSome { type T has a Numeric[T] instance in scope }) = { val n= implicitly[...] // obtain the Numeric instance for x n.negate(x) // and use it with x } In words: I need a type class instance for my input argument, but I don't care about the argument's type, I just need to obtain the instance and use it on my argument. It doesn't have to be an existential type, but I need to avoid type parameters in the def's signature. Thanks.

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• Why repeat database constraints in models?

  - by BWelfel

  In a CakePHP application, for unique constraints that are accounted for in the database, what is the benefit of having the same validation checks in the model? I understand the benefit of having JS validation, but I believe this model validation makes an extra trip to the DB. I am 100% sure that certain validations are made in the DB so the model validation would simply be redundant. The only benefit I see is the app recognizing the mistake and adjusting the view for the user accordingly (repopulating the fields and showing error message on the appropriate field; bettering the ux) but this could be achieved if there was a constraint naming convention and so the app could understand what the problem was with the save (existing method to do this now?)

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• Add Unique Key For Nullable Columns - SQL Server

  - by Ruby

  I'm using sql server 2008 R2 and would like to apply unique key constraint to nullable columns. This code works good, but if I have multiple columns to add this rule to, it would generate as many 'nullbuster' columns. ALTER TABLE tblBranch ADD nullbuster AS (CASE WHEN column1 IS NULL THEN BranchID ELSE NULL END); CREATE UNIQUE INDEX UK_Column1 ON tblBranch(column1,nullbuster); tblBranch is the table name, nullbuster would be the new column name, BranchId is the Primary key column of the target table, and Column1 is the column name of the target column. Is there any way that I could achieve the goal without generating new columns.

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• what are the various approaches for generating PDFs?

  - by andthereitgoes

  I have an idea for an app that would take some flash content which contains graphics and images like various geometric shapes and polygons and some random images and convert them to PDF. Also, since I envision this app to be used my multiple users I want this process to be quick and scalable. One possible solution I could think of is have a small flash client with the capability of assembling the above mentioned graphics and images. Generate some sort of XML, send it to a server running a Java process which could render the PDF using iText. I was wondering what are the other possible ways to do it or the best practices. Technology isn't an issue; open source or commercial. I am looking for ideas to make the process fast and scalable. Most importantly, I don't want the back end server side PDF render engine to constraint the flash client capabilities. I would appreciate if you could share your tech stack idea. Thanks a lot!

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• Using Rails, how can I set my primary key to not be an integer-typed column?

  - by Rudd Zwolinski

  I'm using Rails migrations to manage a database schema, and I'm creating a simple table where I'd like to use a non-integer value as the primary key (in particular, a string). To abstract away from my problem, let's say there's a table employees where employees are identified by an alphanumeric string, e.g. "134SNW". I've tried creating the table in a migration like this: create_table :employees, {:primary_key => :emp_id} do |t| t.string :emp_id t.string :first_name t.string :last_name end What this gives me is what seems like it completely ignored the line t.string :emp_id and went ahead and made it an integer column. Is there some other way to have rails generate the PRIMARY_KEY constraint (I'm using PostgreSQL) for me, without having to write the SQL in an execute call? NOTE: I know it's not best to use string columns as primary keys, so please no answers just saying to add an integer primary key. I may add one anyway, but this question is still valid.

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• Is there any difference between SQL running in code vs the MySQL command line?

  - by MJB

  I have a SQL update statement I am running from inside a PHP program. It is prepared and then executed. When I run it in PHP, it reports a constraint violation. When I run the exact same statement from the command line (which I am getting via dBug()), it works with no errors. This sounds impossible, so I keep looking for differences between the statements. The only thing I can see is that when I execute it with an array of arguments, they all appear to be chars, when some should be integers. Any suggestions for where to look? I can post the code, but that does not seem like it would be helpful, because the code works.

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• MySQL Full-text Search Workaround for innoDB tables

  - by Rob

  I'm designing an internal web application that uses MySQL as its backend database. The integrity of the data is crucial, so I am using the innoDB engine for its foreign key constraint features. I want to do a full-text search of one type of records, and that is not supported natively with innoDB tables. I'm not willing to move to MyISAM tables due to their lack of foreign key support and due to the fact that their locking is per table, not per row. Would it be bad practice to create a mirrored table of the records I need to search using the MyISAM engine and use that for the full-text search? This way I'm just searching a copy of the data and if anything happens to that data it's not as big of a deal because it can always be re-created. Or is this an awkward way of doing this that should be avoided? Thanks.

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• How to generate distinct random numbers per distinct threads in .NET?

  - by mark

  Dear ladies and sirs. I have to generate 19 bit random numbers. However, there is a constraint - two threads may not generate the same random number when running certain code. The simplest solution is lock the entire code. However, I would like to know if there is a non locking solution. I thought, I can incorporate ManagedThreadId within the produced random numbers, but the ManagedThreadId documentation on the Internet mentions that it may span the whole Int32 range. Unmanaged thread id seems to be limited to 11 bits, still this leaves me with just 8 truly random bits. Are there any other ways? Somehow to utilize the Thread Local Storage, may be? Thanks.

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• Fluent Nhibernate mapping related items

  - by Josh

  I am trying to relate 2 items. I have a table that is simply an Id field, and then 2 columns for the Item Id's to relate. I want it to be a 2 way relationship - that is, if the items appear twice in the table, I only want one relationship connection back. So, here's my item: public class Item { public virtual Guid ItemId {get; set;} public virtual string Name {get; set;} public virtual IList<Item> RelatedItems {get; set;} } The table for relating the items looks like this: CREATE TABLE RelatedItems ( RelatedItemId uniqueidentifier NOT NULL, ItemId uniqueidentifier NOT NULL, RelatedId uniqueidentifier NOT NULL, CONSTRAINT PK_RelatedItems PRIMARY KEY CLUSTERED (RelatedItemId) ) What is the best way to map this connection?

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• How can I ask Hibernate to create an index on a foreign key (JoinColumn)?

  - by Kent Chen

  Hi, This is my model. class User{ @CollectionOfElements @JoinTable(name = "user_type", joinColumns = @JoinColumn(name = "user_id")) @Column(name = "type", nullable = false) private List<String> types = new ArrayList<String>(); } You can imagin there would be a table called "user_type", which has two columns, one is "user_id", the other is "type". And when I use hbm2ddl to generate the ddls, I can have this table, along with the foreign key constraint on "user_id". However, there is no index of this for this column. And I need this index. How can I let hibernate to generate this index for me? Thank you!

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• Find all possible partitions of n elements with k-sized subsets, where two elements share same set o

  - by ypnos

  I have n=32 elements that need to be partitioned into 8 sets, each set has to hold exactly k=4 elements. I need to find all possible partitions with the constraint that each pair of elements only shares the same set once. So if I start with [1 2 3 4] [5 6 7 8] [...], all consecutive partitions cannot hold e.g. [1 2 X X] or [X X 1 3]. sets are unordered. Close to this problem are the stirling numbers of the second kind. However, they only solve the problem for arbitrarily sized sets.

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• Find node level in a tree

  - by Álvaro G. Vicario

  I have a tree (nested categories) stored as follows: CREATE TABLE `category` ( `category_id` int(10) unsigned NOT NULL AUTO_INCREMENT, `category_name` varchar(100) NOT NULL, `parent_id` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`category_id`), UNIQUE KEY `category_name_UNIQUE` (`category_name`,`parent_id`), KEY `fk_category_category1` (`parent_id`,`category_id`), CONSTRAINT `fk_category_category1` FOREIGN KEY (`parent_id`) REFERENCES `category` (`category_id`) ON DELETE SET NULL ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_spanish_ci I need to feed my client-side language (PHP) with node information (child+parent) so it can build the tree in memory. I can tweak my PHP code but I think the operation would be way simpler if I could just retrieve the rows in such an order that all parents come before their children. I could do that if I knew the level for each node: SELECT category_id, category_name, parent_id FROM category ORDER BY level -- No `level` column so far :( Can you think of a way (view, stored routine or whatever...) to calculate the node level? I guess it's okay if it's not real-time and I need to recalculate it on node modification.

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• Which language should I learn to create a sudoku game?

  - by Brandan

  I'd like to learn a new programming language, something besides all the scripting languages I've used for the past many years (Ruby, JavaScript, Perl, PHP, bash). I figured it might be interesting to make a sudoku game since there are plenty of documented algorithms and it only requires fairly simple data structures. It might start out as either a generator or a solver of puzzles, not necessarily both and not necessarily with a GUI. My goal is primarily to learn some new programming concepts beyond MVC and UI design, secondarily for this thing to be pretty fast. Is there a language that particularly shines for these sorts of constraint satisfaction problems? Is it suited to a functional language like Haskell or a highly concurrent language like Erlang (say for solving puzzles much larger than 9 x 9)? Or is this question mostly meaningless?

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• copy an identity column into another table

  - by slake

  I have 2 tables that are related,both have identity columns for primary keys and i am using a vb form to insert data into them,My problem is that i cannot get the child table to get the primary key of the parent table and use this as its foreign key in my database. the data is inserted fine though no foreign key constraint is made.I am wondering if a trigger will do it and if so how. All my inserting of data is done in vb. The user wont insert any keys. all these are identity columns that are auto generated. If a trigger is my way out please illustrate with an example. If there is another way i can do this in VB itself then please advise and an example will be greatly appreciated Thanks in advance

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• F# equivalent of the C# typeof(IEnumerable<>)

  - by Rune FS

  I have a piece of code where I need to figure out if a given type implements IEnumerable (I don't care about the T) I've tried (t:System.Type in case you wonder) let interfaces = t.GetInterfaces() let enumerbale = interfaces.Any( fun t -> (t.GetGenericTypeDefinition() = typeof<IEnumerable<>>) however that wont compile (the compile don't like the <). I then tried let interfaces = t.GetInterfaces() let enumerbale = interfaces.Any( fun t -> (t.GetGenericTypeDefinition() = typeof<IEnumerable<'a>>) but get's a warning that 'a is constraint to obj. I Don't want to figure out if IEnumerable is implemented but IEnumerabl<. Any one know's the solution and btw feel free to comment on the code above as well. It's my first non-trivial F# program

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• SQL insert default value

  - by Stan

  Say if I have a table like CREATE TABLE [Message] ( [MessageIdx] [int] IDENTITY (1, 1) NOT NULL , [Message] [varchar] (1024) COLLATE Latin1_General_CI_AS NOT NULL , [ValidUntil] [datetime] NULL , CONSTRAINT [PK_Message] PRIMARY KEY CLUSTERED ( [MessageIdx] ) WITH FILLFACTOR = 90 ON [PRIMARY] ) ON [PRIMARY] GO I am trying to insert value without specify column names explicitly. Below statement causes error. How can I do that? Thanks. set identity_insert caconfig..fxmessage on; insert into message values (DEFAULT,'blah',DEFAULT); set identity_insert caconfig..fxmessage off;

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• Can a parser tell the lexer to ignore a newline?

  - by chollida

  I'm writing a preprocessor for my language. In the preprocessor I've output a line that wasn't in the source file. This causes any error messages that Anltr creates to be incremented by one line. The Lexer handles the line count so I'm wondering if there is a way for the parser to tell the lexer to decrement the line count, or to ignore a specific newline. I'm also open to other suggestions on how to work around this. The only constraint I have is putting the extra line inline with the existing code. I'd prefer to keep it on it's own line to keep my parsing sane.

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• How to manage reports/files distribution to different destinations in Unix?

  - by mossie

  The reporting tools will generate a huge numbers of reports/files in the file system (a Unix directory). There's a list of destinations (email addresses and shared folders) where a different set of reports/files (can have overlap) are required to be distributed at each destinations. Would like to know if there's a way to efficiently manage this reports delivery using shell scripts so that the maintenance of the list of reports and destinations will not become a mess in future. It's quite an open ended question, the constraint however is that it should work within the boundaries of managing the reports in a Unix FS.

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• how to check if entity already exists in database before inserting in doctrine?

  - by fayer

  whenever i insert a entity that already exists in database (i have a unique constraint on email) i get an error message on the screen. so i want to check if it already exists, if not i insert it. at the moment it looks like this: $q = Doctrine_Query::create() ->from('User u') ->where('u.email = ?', $email); $object = $q->fetchOne(); if( ! is_object($object)) { $user = new User(); $user-email = $email; $user->save(); } i wonder, if there an easier way to do this? thanks

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• Why does Generic class signature requires specifying new() if type T needs instantiation ?

  - by this. __curious_geek

  I'm writing a Generic class as following. public class Foo<T> : where T : Bar, new() { public void MethodInFoo() { T _t = new T(); } } As you can see the object(_t) of type T is instantiated at run-time. To support instantiation of generic type T, language forces me to put new() in the class signature. I'd agree to this if Bar is an abstract class but why does it need to be so if Bar standard non-abstract class with public parameter-less constructor. compiler prompts following message if new() is not found. Cannot create an instance of the variable type 'T' because it does not have the new() constraint

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• Loop through different sets of unique permutations

  - by user558610

  Hi I'm having a hard time getting started to layout code for this problem. I have a fixed amount of random numbers, in this case 8 numbers. R[] = { 1, 2, 3, 4, 5, 6, 7, 8 }; That are going to be placed in 3 sets of numbers, with the only constraint that each set contain minimum one value, and each value can only be used once. For example: R1[] = { 1, 4 } R2[] = { 2, 8, 5, 6 } R3[] = { 7, 4 } I need to loop through all possible combinations of a set R1, R2, R3. Order is not important, so if the above example happened, I don't need R1[] = { 4, 1 } R2[] = { 2, 8, 5, 6 } R3[] = { 7, 4 } NOR R1[] = { 2, 8, 5, 6 } R2[] = { 7, 4 } R3[] = { 1, 4 } What is a good method?

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