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• Manage Foreign key and Drop downlist for optional field in .NET

  - by Brij

  What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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• T-SQL foreign key check constraint

  - by PaN1C_Showt1Me

  When you create a foreign key constraint in a table and you create the script in MS SQL Management Studio, it looks like this. ALTER TABLE T1 WITH CHECK ADD CONSTRAINT FK_T1 FOREIGN KEY(project_id) REFERENCES T2 (project_id) GO ALTER TABLE T1 CHECK CONSTRAINT FK_T1 GO What I don't understand is what purpose has the second alter with check constraint. Isn't creating the FK constraint enough? Do you have to add the check constraint to assure reference integrity ? Another question: how would it look like then when you'd write it directly in the column definition? CREATE TABLE T1 ( my_column INT NOT NULL CONSTRAINT FK_T1 REFERENCES T2(my_column) ) Isn't this enough?

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• linq to sql using foreign keys returning iqueryable(of myEntity]

  - by Gern Blandston

  I'm trying to use Linq to SQL to return an IQueryable(of Project) when using foreign key relationships. Using the below schema, I want to be able to pass in a UserId and get all the projects created for the company the user is associated with. DB tables: Projects Projid ProjCreator FK (UserId from UserInfo table) Companyid FK (CompanyID from Companies table) UserInfo UserID PK Companyid FK Companies CompanyId PK Description I can get the iqueryable(of project) when simply getting the ProjectCreator with this: Return (From p In db.Projects _ Where p.ProjectCreator = Me.UserId) But I'm having trouble getting the syntax to get a iqueryable(of projects) when using foreign keys. Below gives me an IQueryable(of anonymous) but I can't seem to convince it to give me an IQueryable(of project) even if I try to cast it: Dim retval = (From p In db.Projects _ Join c In db.Companies On p.CompanyId Equals c.CompanyId _ Join u In db.UserInfos On u.CompanyId Equals c.CompanyId _ Where u.Login = UserId)

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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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• Multiple foreign keys from one table linking to single primary key in second table

  - by croker10

  Hi all, I have a database with three tables, a household table, an adults table and a users table. The Household table contains two foreign keys, iAdult1ID and iAdult2ID. The Users table has a iUserID primary key and the Adult table has a corresponding iUserID foreign key. One of the columns in the Users table is strUsername, an e-mail address. I am trying to write a query that will allow me to search for an e-mail address for either adult that has a relation to the household. So I have two questions, assuming that all the values are not null, how can I do this? And two, in reality, iAdult2ID can be null, is it still possible to write a query to do this? Thanks for your help. Let me know if you need any more information.

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• PostgreSQL: How to index all foreign keys?

  - by biggusjimmus

  I am working with a large PostgreSQL database, and I are trying to tune it to get more performance. Our queries and updates seem to be doing a lot of lookups using foreign keys. What I would like is a relatively simple way to add Indexes to all of our foreign keys without having to go through every table (~140) and doing it manually. In researching this, I've come to find that there is no way to have Postgres do this for you automatically (like MySQL does), but I would be happy to hear otherwise there, too.

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• How to handle Foreign key for optional field in .NET

  - by brz dot net

  What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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• SQL - Dervied Foreign Key - Possible?

  - by Chad

  I'm just curious if this is possible, specifically in SQL CE (Express) with support in .NET's Entity Framework: Table1 (primary) -nvarchar(2000) url -... Table2 (with foreign key) -nvarchar(2000) domain -... foreign key on Table2.domain references Table1.url such that Table.url contains Table2.domain e.g. Table1: http://www.google.com/blah/blah http://www.cnn.com/blah/ http://www.google.com/foo Table2: google.com cnn.com Is it possible for this to be scripted and enforced by SQL CE (let alone any relation database) and, if so, can .NET's Entity Framework automatically support this if I import my database into a model?

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• Cannot add or update a child row: a foreign key constraint fails

  - by myaccount

  // Getting the id of the restaurant to which we are uploading the pictures $restaurant_id = intval($_GET['restaurant-id']); if(isset($_POST['submit'])) { $tmp_files = $_FILES['rest_pics']['tmp_name']; $target_files = $_FILES['rest_pics']['name']; $tmp_target = array_combine($tmp_files, $target_files); $upload_dir = $rest_pics_path; foreach($tmp_target as $tmp_file => $target_file) { if(move_uploaded_file($tmp_file, $upload_dir."/".$target_file)) { $sql = sprintf(" INSERT INTO rest_pics (branch_id, pic_name) VALUES ('%s', '%s')" , mysql_real_escape_string($restaurant_id) , mysql_real_escape_string(basename($target_file))); $result = mysql_query($sql) or die(mysql_error()); } I get the next error: Cannot add or update a child row: a foreign key constraint fails (rest_v2.rest_pics, CONSTRAINT rest_pics_ibfk_1 FOREIGN KEY (branch_id) REFERENCES rest_branches (branch_id) ON DELETE CASCADE ON UPDATE CASCADE However, this error totally disappears and everything goes well when I put directly the restaurant id (14 for example) instead of $restaurant_id variable in the sql query. The URL am getting the id from is: http://localhost/rest_v2/public_html/admin/add-delete-pics.php?restaurant-id=2 Any help please?

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• Error 1005 when adding a foreign key constraint on mysql table

  - by luc

  Hello, I have a problem when upgrading a django and mysql app with south. I've tried to make a sql-based upgrade with the code generated by the django sqlall command and I have a similar problem. Here is the sql code: CREATE TABLE `programmations_basissupport` ( `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `value` numeric(6, 0) NOT NULL ) ALTER TABLE `programmations_concert` ADD `basis_support_id` integer AFTER program_status_id; ALTER TABLE `programmations_concert` ADD CONSTRAINT `basis_support_id_refs_id_1e4ed8d7` FOREIGN KEY (`basis_support_id`) REFERENCES `programmations_basissupport` (`id`); An error is raised when adding the FK constraint: ERROR 1005 (HY000): Can't create table 'apidev_mnl.#sql-106e_632b00a' (errno: 150) Does anybody have an idea? Update: DEFAULT values where missing but even if I add the default='' in the django model, the creation of foreign keys fails. Thanks for your help

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• Working with Foreign languages

  - by Matt

  My DB needs to hold strings containing foreign language characters such that; User enters string into form, form submitted and string added to DB, string will be displayed on page for viewing. I would like to use UTF8 as this will be able to handle all of the required languages. Currently I believe my DB is set to 'latin1' but webpages are capable of displaying correct charachters anyways. Problems arise when trying to set textareas to hold foreign charachters and when viewing DB via command-line. How can I implement this most effectively? My plan was to blitz the whole site such that:DB Charset is UTF8 and web pages charset is UTF8. Could someone give me the minimal commands on how to do this so I don't end up duplicating things (Having "UTF8" commands everywhere when I really just need one) and making things too difficult to control. Newbie Thanks

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• Variable declaration versus assignment syntax

  - by rwallace

  Working on a statically typed language with type inference and streamlined syntax, and need to make final decision about syntax for variable declaration versus assignment. Specifically I'm trying to choose between: // Option 1. Create new local variable with :=, assign with = foo := 1 foo = 2 // Option 2. Create new local variable with =, assign with := foo = 1 foo := 2 Creating functions will use = regardless: // Indentation delimits blocks square x = x * x And assignment to compound objects will do likewise: sky.color = blue a[i] = 0 Which of options 1 or 2 would people find most convenient/least surprising/otherwise best?

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• Are programming languages pretty much "stable" for now?

  - by Sauron

  Recently i have looked at the "timeline" of Programming Languages and while a lot has changed in the past 5-10 years, there are a lot of languages that have pretty much "stayed" the same in their niche/use. For example, let's take C language. We don't really ever see much languages being developed (correct me if i'm wrong) to try to Unseat C. However, there are a lot of languages that try to do similar things (look at all the SQL/No-SQL languages) Scripting Languages, etc... Is there a reason for this trend? Or is it just because C was designed very well ? and there isn't really any need for new once?

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• What is the annoying/lacking feature in C#, in your opinion?

  - by Vimvq1987

  To be honest, I'm working with C# everyday, and I can say that I love its elegant syntax. But no language is perfect, so does C#. In my opinion, these two features are missing: Full-featured enum. I was pretty happy with enum in C#, until I know about enum in Java. Of course, we can "simulate" a full-featured enum in C# by class, but it's much better if Microsoft simplify this. Immutable keyword. We are told to let a class/struct immutable whenever possible. But to do that, we have to add readonly keyword to every field, and then if we add setter by a mistake, our class will be mutable, and nobody knows. By immutable keyword, every field will be automatically readonly, and any setter will be prohibited (error when compile). It's like static keyword added to class in C# 2.0 well. what's is your annoying/lacking feature in C#?

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• Design a mini script language

  - by radi

  hi , my project this year is to develop a text mining tool (with new features) so we need a mini script language in this tool to add annotation to texts this language should be simple and like lisp grammars (left and right side) . what i need is how to design this language ,i know how to constract the compiler , but how to write language grammars ? , and i want to use some mini open source language or any language bnf please advice me and if there is a language i can use and customize to meet my needs ? thanks

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• What do I need to know to design a language and write a interpreter for it?

  - by alFReD NSH

  I know this question has been asked and even there are thousands of books and articles about it. But the problem is that there are too many, and I don't know are they good enough, I have to design a language and write a interpreter for it. The base language is javascript (using nodejs) but it's ok if the compiler was written in another language that I can use from node. I had done a research about compiler compilers in JS, there is jison (Bison implementaion in JS), waxeye, peg.js. I decided to give jison a try, due to the popularity and its being used by coffee script, so it should be able to cover my language too. The grammar definition syntax is similar to bison. But when I tried read the bison manual it seemed very hard to understand for me. And I think it's because I don't know a lot of things about what I'm doing. Like I don't what is formal language theory. I am experienced in Javascript (I'm more talented in JS than most average programmers). And also know basic C and C++ (not much experience but can write a working code for basic things). I haven't had any formal education, so I may not be familiar with some software engineering and computer science principles. Though everyday I try to grasp a lot of articles and improve. So I'm asking if you know any good book or article that can help me. Please also write why the resource you're suggesting is good. --update-- The language I'm trying to create, is not really complicated. All it has is expressions (with or without units), comparisons and logical operators. There are no functions, loops, ... The goal is to create a language that non-programmers can easily learn. And to write customized validations and calculations.

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• What do you wish language designers paid attention to?

  - by Berin Loritsch

  The purpose of this question is not to assemble a laundry list of programming language features that you can't live without, or wish was in your main language of choice. The purpose of this question is to bring to light corners of languge design most language designers might not think about. So, instead of thinking about language feature X, think a little more philisophically. One of my biases, and perhaps it might be controversial, is that the softer side of engineering--the whys and what fors--are many times more important than the more concrete side. For example, Ruby was designed with a stated goal of improving developer happiness. While your opinions may be mixed on whether it delivered or not, the fact that was a goal means that some of the choices in language design were influenced by that philosophy. Please do not post: Syntax flame wars (I could care less whether you use whitespace [Python], keywords [Ruby], or curly braces [Java, C/C++, et. al.] to denote program blocks). That's just an implementation detail. "Any language that doesn't have feature X doesn't deserve to exist" type comments. There is at least one reason for all programming languages to exist--good or bad. Please do post: Philisophical ideas that language designers seem to miss. Technical concepts that seem to be poorly implemented more often than not. Please do provide an example of the pain it causes and if you have any ideas of how you would prefer it to function. Things you wish were in the platform's common library but seldom are. One the same token, things that usually are in a common library that you wish were not. Conceptual features such as built in test/assertion/contract/error handling support that you wish all programming languages would implement properly--and define properly. My hope is that this will be a fun and stimulating topic.

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• Merge replication server side foreign key violation from unpublished table

  - by Reiste

  We are using SQL Server 2005 Merge Replication with SQL CE 3.5 clients. We are using partitions with filtering for the separate subscriptions, and nHibernate for the ORM mapping. There is automatic ID range management from SQL Server for the subscriptions. We have a table, Item, and a table with a foreign key to Item - ItemHistory. Both of these are replicated down, filtered according to the subscription. Item has a column called UserId, and is filtered per subscription with this filter: WHERE UserId IN (SELECT... [complicated subselect]...) ItemHistory hangs off Item in the publication filter articles. On the server, we have a table ItemHistoryExport, which has a foreign key to ItemHistory. ItemHistoryExport is not published. Entries in the Item and ItemHistory tables are never deleted, on the server or the client. However, the "ownership" of items (and hence their ItemHistories) MAY change, which causes them to be moved from one client subscription/partition to another from time to time. When we sync, we occasionally get the following error: A row delete at '48269404 - 4108383dbb11' could not be propagated to 'MyServer\MyInstance.MyDatabase'. This failure can be caused by a constraint violation. The DELETE statement conflicted with the REFERENCE constraint "FK_ItemHistoryExport_ItemHistory". The conflict occurred in database "MyDatabase", table "dbo.ItemHistoryExport", column 'ItemHistoryId'. Can anyone help us understand why this happens? There shouldn't ever be a delete happening on the server side.

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• Can I use foreign key restrictions to return meaningful UI errors with PHP

  - by Shane

  I want to start by saying that I am a big fan of using foreign keys and have a tendency to use them even on small projects to keep my database from being filled with orphaned data. On larger projects I end up with gobs of keys which end up covering upwards of 8 - 10 layers of data. I want to know if anyone could suggest a graceful way of handling 'expected errors' from the MySQL database in a way that I can construct meaningful messages for the end user. I will explain 'expected errors' with an example. Lets say I have a set of tables used for basic discussions: discussion questions responses users Hierarchically they would probably look something like this: -users --discussion ---questions ----responses When I attempt to delete a user the FKs will check discussions and if any discussion exist the deletion is restricted, deleting discussion checks questions, deleting questions checks responses. An 'expected error' in this case would be attempting to delete a user--unless they are newly created I can anticipate that one or more foreign keys will fail causing an error. What I WANT to do is to catch that error on deletion and be able to tell the end user something like 'We're sorry, but all discussions must be removed before you can delete this user...'. Now I know I can keep and maintain matching arrays in PHP and map specific errors to messages but that is messy and prone to becoming stagnant, or I could manually run a set of selects prior to attempting the deletion, but then I am doing just as much work as without using FKs. Any help here would be greatly appreciated, or if I am just looking at this completely wrong then please let me know. On a side note I generally use CodeIgniter for my application development, so if that would open up an avenue through that framework please consider that in your answers. Thanks in Advance

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• Sort queryset by a generic foreign key (django)?

  - by thornomad

  I am using Django's comment framework which utilizes generic foreign keys. Question: How do I sort a given model's queryset by their comment count using the generic foreign key lookup? Reading the django docs on the subject it says one needs to calculate them not using the aggregation API: Django's database aggregation API doesn't work with a GenericRelation. [...] For now, if you need aggregates on generic relations, you'll need to calculate them without using the aggregation API. The only way I can think of, though, would be to iterate through my queryset, generate a list with content_type and object_id's for each item, then run a second queryset on the Comment model filtering by this list of content_type and object_id ... sort the objects by the count, then re-create a new queryset in this order by pulling the content_object for each comment ... This just seems wrong and I'm not even sure how to pull it off. Ideas? Someone must have done this before. I found this post online but it requires me handwriting SQL -- is that really necessary ?

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• List all foreign key constraints that refer to a particular column in a specific table

  - by Sid

  I would like to see a list of all the tables and columns that refer (either directly or indirectly) a specific column in the 'main' table via a foreign key constraint that has the ON DELETE=CASCADE setting missing. The tricky part is that there would be an indirect relationships buried across up to 5 levels deep. (example: ... great-grandchild- FK3 = grandchild = FK2 = child = FK1 = main table). We need to dig up the leaf tables-columns, not just the very 1st level. The 'good' part about this is that execution speed isn't of concern, it'll be run on a backup copy of the production db to fix any relational issues for the future. I did SELECT * FROM sys.foreign_keys but that gives me the name of the constraint - not the names of the child-parent tables and the columns in the relationship (the juicy bits). Plus the previous designer used short, non-descriptive/random names for the FK constraints, unlike our practice below The way we're adding constraints into SQL Server: ALTER TABLE [dbo].[UserEmailPrefs] WITH CHECK ADD CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId]) REFERENCES [dbo].[UserMasterTable] ([UserId]) ON DELETE CASCADE GO ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] GO The comments in this SO question inpire this question.

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• windows xp mode for windows 7 - save text input language settings

  - by Gero

  When I change the 'default language' in 'text services and input languages' in windows xp mode from EN-US to DE-DE the settings are reverted with the next logoff / reboot - EN-US is the default language again. Is there a way around this behaviour? I'm using the default 'XPMUser' in windows xp mode. I also checked 'turn off advanced text services' and disabled the language bar and windows xp remembers these settings - just not the default language..

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• windows xp mode for windows 7 - save text input language settings

  - by Gero

  When I change the 'default language' in 'text services and input languages' in windows xp mode from EN-US to DE-DE the settings are reverted with the next logoff / reboot - EN-US is the default language again. Is there a way around this behaviour? I'm using the default 'XPMUser' in windows xp mode. I also checked 'turn off advanced text services' and disabled the language bar and windows xp remembers these settings - just not the default language..

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• [rails] do we need database level constraints

  - by shrimpy

  i have the same problem as in the following post http://stackoverflow.com/questions/1451570/ruby-on-rails-database-migration-not-creating-foreign-keys-in-mysql-tables so i am wondering, why rails do not support generate foreign key by default??? it is not necessary??? or we suppose to do it manually?

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• Thoughts on my new template language?

  - by Ralph

  Let's start with an example: using "html5" using "extratags" html { head { title "Ordering Notice" jsinclude "jquery.js" } body { h1 "Ordering Notice" p "Dear @name," p "Thanks for placing your order with @company. It's scheduled to ship on {@ship_date|dateformat}." p "Here are the items you've ordered:" table { tr { th "name" th "price" } for(@item in @item_list) { tr { td @item.name td @item.price } } } if(@ordered_warranty) p "Your warranty information will be included in the packaging." p(class="footer") { "Sincerely," br @company } } } The "using" keyword indicates which tags to use. "html5" might include all the html5 standard tags, but your tags names wouldn't have to be based on their HTML counter-parts at all if you didn't want to. The "extratags" library for example might add an extra tag, called "jsinclude" which gets replaced with something like <script type="text/javascript" src="@content"></script> Tags can be optionally be followed by an opening brace. They will automatically be closed as the closing brace. If no brace is used, they will be closed after taking on element. Variables are prefixed with the @ symbol. They may be used inside double-quoted strings. I think I'll use single-quotes to indicate "no variable substitution" like PHP does. Filter functions can be applied to variables like @variable|filter. Arguments can be passed to the filter @variable|filter:@arg1,arg2="y" Attributes can be passed to tags by including them in (), like p(class="classname"). Some questions: Which symbol should I use to prefix variables? @ (like Razor), $ (like PHP), or something else? Should the @ symbol be necessary in "for" and "if" statements? It's kind of implied that those are variables. Tags and controls (like if,for) presently have the exact same syntax. Should I do something to differentiate the two? If so, what? Do you like the attribute syntax? (round brackets) I'll add more questions in a few minutes, once I get some feedback.

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