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  • Queries with Multiple Constraints

    - by ANITHA
    I have the following tables and fields: +------------------+ +-------------------+ +---------------+ | Request | | RequestItem | | Item | +------------------+ +-------------------+ +---------------+ | + Requester_Name | | + Request_No | | + Item | +------------------+ +-------------------+ +---------------+ | + Request_No | | + Item | +------------------+ +-------------------+ I would like to filter the items which are selected under a particular request number, along with a specific requester name. How might I go about doing this?

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  • Deleting objects with FK constraints in Spring/Hibernate

    - by maxdj
    This seems like such a simple scenario to me, yet I cannot for the life of my find a solution online or in print. I have several objects like so (trimmed down): @Entity public class Group extends BaseObject implements Identifiable<Long> { private Long id; private String name; private Set<HiringManager> managers = new HashSet<HiringManager>(); private List<JobOpening> jobs; @ManyToMany(fetch=FetchType.EAGER) @JoinTable( name="group_hiringManager", joinColumns=@JoinColumn(name="group_id"), inverseJoinColumns=@JoinColumn(name="hiringManager_id") ) public Set<HiringManager> getManagers() { return managers; } @OneToMany(mappedBy="group", fetch=FetchType.EAGER) public List<JobOpening> getJobs() { return jobs; } } @Entity public class JobOpening extends BaseObject implements Identifiable<Long> { private Long id; private String name; private Group group; @ManyToOne @JoinColumn(name="group_id", updatable=false, nullable=true) public Group getGroup() { return group; } } @Entity public class HiringManager extends User { @ManyToMany(mappedBy="managers", fetch=FetchType.EAGER) public Set<Group> getGroups() { return groups; } } Say I want to delete a Group object. Now there are dependencies on it in the JobOpening table and in the group_hiringManager table, which cause the delete function to fail. I don't want to cascade the delete, because the managers have other groups, and the jobopenings can be groupless. I have tried overriding the remove() function of my GroupManager to remove the dependencies, but it seems like no matter what I do they persist, and the delete fails! What is the right way to remove this object?

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  • Cannot set g:checkbox to off for a child on one-to-many relationship

    - by icon911
    Got a weird issue with g:checkbox not being saved when its switched from on to off for a child in one-to-many relationship. For example: class Parent { Boolean enabled static hasMany = [children: Child] static constraints = { enabled(blank: true, nullable: true) } } class Child { Boolean enabled static belongsTo = [parent: Parent] static constraints = { enabled(blank: true, nullable: true) } } Posting to Parent controller true/false values will work for Parent: <g:checkBox name="enabled" value="${parentInstance?.enabled}"/> However, not for Child! When posting to Parent controller I can only go from false to true, trying to change from true to false again will not work: <g:each in="${parentInstance.children}" status="i" var="child"> <g:checkBox name="child[${i}].enabled" value="${child?.enabled}" /> </g:each> That seems to be a bug. Any ideas? Thanks.

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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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  • OCL constraints intended prevent node creation in an GMF generated editor only makes it invisible

    - by TheMorph
    Hello, I am working on editors created with GMF and struggling with OCL right now. Is there a possibilty to prevent a node to be created if an OCL statement in the mapping evaluates to false? If tried adding an OCL statement to a node and all it does is making the node not visible in the editor, but it is created. There is also an OCL statement in the ecore file, but this way it is only evaluated when there should be something done with the created model. I does not prevent a user to construct an invalid model but this is what I intend to prevent. Thanks in advance, Morph

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  • How to use constraint programming for optimizing shopping baskets?

    - by tangens
    I have a list of items I want to buy. The items are offered by different shops and different prices. The shops have individual delivery costs. I'm looking for an optimal shopping strategy (and a java library supporting it) to purchase all of the items with a minimal total price. Example: Item1 is offered at Shop1 for $100, at Shop2 for $111. Item2 is offered at Shop1 for $90, at Shop2 for $85. Delivery cost of Shop1: $10 if total order < $150; $0 otherwise Delivery cost of Shop2: $5 if total order < $50; $0 otherwise If I buy Item1 and Item2 at Shop1 the total cost is $100 + $90 +$0 = $190. If I buy Item1 and Item2 at Shop2 the total cost is $111 + $85 +$0 = $196. If I buy Item1 at Shop1 and Item2 at Shop2 the total cost is $100 + $10 + $85 + $0 = 195. I get the minimal price if I order Item1 and Item2 at Shop1: $190 What I tried so far I asked another question before that led me to the field of constraint programming. I had a look at cream and choco, but I did not figure out how to create a model to solve my problem. | shop1 | shop2 | shop3 | ... ----------------------------------------- item1 | p11 | p12 | p13 | item2 | p21 | p22 | p23 | . | | | | . | | | | ----------------------------------------- shipping | s1 | s2 | s3 | limit | l1 | l2 | l3 | ----------------------------------------- total | t1 | t2 | t3 | ----------------------------------------- My idea was to define these constraints: each price "p xy" is defined in the domain (0, c) where c is the price of the item in this shop only one price in a line should be non zero if one or more items are bought from one shop and the sum of the prices is lower than limit, then add shipping cost to the total cost shop total cost is the sum of the prices of all items in a shop total cost is the sum of all shop totals The objective is "total cost". I want to minimize this. In cream I wasn't able to express the "if then" constraint for conditional shipping costs. In choco these constraints exist, but even for 5 items and 10 shops the program was running for 10 minutes without finding a solution. Question How should I express my constraints to make this problem solvable for a constraint programming solver?

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  • Django filter with two constraints on related model

    - by BJ Homer
    I have a django app with models as follows: A Question model An Answer model, with a ForeignKey back to the Question. (A question can have multiple answers.) A Flag model, with a ForeignKey to the Answer. (An answer can be flagged as inappropriate.) All of the above also have a user field, defining the user that created that object. I'm trying to get a list of all Questions with answers from the current user which have been flagged. I tried this: Question.objects.filter(answer__user=user).\ filter(answer__flag__isnull=True).distinct() … but I believe that will return a list of Questions with answers from the current user and with answers which have been flagged, but will not necessarily guarantee that it is the user's answer that has been flagged. Is there an easy way to do this? Basically, I want to make the answer part of the filter refer to the same answer on both of them. Please let me know if something is unclear.

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  • How to use OCL constraints to prevent node creation in an GMF generated editor

    - by TheMorph
    Hello, I am working on editors created with GMF and struggling with OCL right now. Is there a possibilty to prevent a node to be created if an OCL statement in the mapping evaluates to false? If tried adding an OCL statement to a node and all it does is making the node not visible in the editor, but it is created. There is also an OCL statement in the ecore file, but this way it is only evaluated when there should be something done with the created model. I does not prevent a user to construct an invalid model but this is what I intend to prevent. Thanks in advance, Morph

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  • "Special case" records for foreign key constraints

    - by keithjgrant
    Let's say I have a mysql table, called foo with a foreign key option_id constrained to the option table. When I create a foo record, the user may or may not have selected an option, and 'no option' is a viable selection. What is the best way to differentiate between 'null' (i.e. the user hasn't made a selection yet) and 'no option' (i.e. the user selected 'no option')? Right now, my plan is to insert a special record into the option table. Let's say that winds up with an id of 227 (this table already has a number of records at this point, so '1' isn't available). I have no need to access this record at a database level, and it would act as nothing more than a placeholder that the foreign key in the foo table can reference. So do I just hard-code '227' in my codebase when I'm creating 'foo' records where the user has selected 'no option'? The hard-coded id seems sloppy, and leaves room for error as the code is maintained down the road, but I'm not really sure of another approach.

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  • foreign key constraints on primary key columns - issues ?

    - by zzzeek
    What are the pros/cons from a performance/indexing/data management perspective of creating a one-to-one relationship between tables using the primary key on the child as foreign key, versus a pure surrogate primary key on the child? The first approach seems to reduce redundancy and nicely constrains the one-to-one implicitly, while the second approach seems to be favored by DBAs, even though it creates a second index: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key references parent(id), data varchar(50) ) pure surrogate key: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key, parent_id integer unique references parent(id), data varchar(50) ) the platforms of interest here are Postgresql, Microsoft SQL Server.

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  • Heavy Mysql operation & Time Constraints [closed]

    - by Rahul Jha
    There is a performance issue where that I have stuck with my application which is based on PHP & MySql. The application is for Data Migration where data has to be uploaded and after various processes (Cleaning from foreign characters, duplicate check, id generation) it has to be inserted into one central table and then to 5 different tables. There, an id is generated and that id has to be updated to central table. There are different sets of records and validation rules. The problem I am facing is that when I insert say(4K) rows file (containing 20 columns) it is working fine within 15 min it gets inserted everywhere. But, when I insert the same records again then at this time it is taking one hour to insert (ideally it should get inserted by marking earlier inserted data as duplicate). After going through the log file, I noticed is that there is a Mysql select statement where I am checking the duplicates and getting ID which are duplicates. Then I am calling a function inside for loop which is basically inserting records into 5 tables and updates id to central table. This Calling function is major time of whole process. P.S. The records has to be inserted record by record.. Kindly Suggest some solution.. //This is that sample code $query=mysql_query("SELECT DISTINCT p1.ID FROM table1 p1, table2 p2, table3 a WHERE p2.datatype =0 AND (p1.datatype =1 || p1.datatype=2) AND p2.ID =0 AND p1.ID = a.ID AND p1.coulmn1 = p2.column1 AND p1.coulmn2 = p2.coulmn2 AND a.coulmn3 = p2.column3"); $num=mysql_num_rows($query); for($i=0;$i<$num;$i++) { $f=mysql_result($query,$i,"ID"); //calling function RecordInsert($f); }

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  • how to limit the foreignkey dropdown with constraints?

    - by FurtiveFelon
    Hi all, I have a database which keeps track of interaction between two different teams (represented in the admin interface by two different groups). For some fields, i have a foreignkey to Users database, and i would like to limit the dropdown people to only the specific groups. If anyone have any suggestions, it would be much appreciated! Jason

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  • "Zoom" text to be as big as possible within constraints/box

    - by stolsvik
    First problem: You have 400 pixels width to go on, and need to fit some text within that constraint as large as possible (thus, the text shall use that amount of space). Throw in a new constraint: If the text is just "A", then it shall not zoom this above 100 pixels (or some specific font size). Then, a final situation: Linebreaks. Fit some text in the largest possible way within e.g. 400 x 150 pixels. An obvious way is to simply start with point 1, and then increase until you can't fit it anymore. This would work for all three problems, but would be very crude. The fitting of a single line within bounds could be done by writing it with some fixed point size, check the resulting pixel bounds of the text, and then simply scale it with a transform (the text scales properly too then, check out TransformUI). Any ideas of other ways to attack this would be greatly appreciated!

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  • C# Multiple constraints

    - by John
    I have an application with lots of generics and IoC. I have an interface like this: public interface IRepository<TType, TKeyType> : IRepo Then I have a bunch of tests for my different implementations of IRepository. Many of the objects have dependencies on other objects so for the purpose of testing I want to just grab one that is valid. I can define a separate method for each of them: public static EmailType GetEmailType() { return ContainerManager.Container.Resolve<IEmailTypeRepository>().GetList().FirstOrDefault(); } But I want to make this generic so it can by used to get any object from the repository it works with. I defined this: public static R GetItem<T, R>() where T : IRepository<R, int> { return ContainerManager.Container.Resolve<T>().GetList().FirstOrDefault(); } This works fine for the implementations that use an integer for the key. But I also have repositories that use string. So, I do this now: public static R GetItem<T, R, W>() where T : IRepository<R, W> This works fine. But I'd like to restrict 'W' to either int or string. Is there a way to do that? The shortest question is, can I constrain a generic parameter to one of multiple types?

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  • MySQL foreign key constraints, cascade delete

    - by Cudos
    Hello. I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB). How do I make a SQL statment that DELETE ON CASCADE? Secondly, that using DELETE ON CASCADE. E.g. if I delete a category then it would delete products related to that category even though there are other categories related to those products. The pivot table "categories_products" creates a many-to-many relationship between the two other tables. categories - id (INT) - name (VARCHAR 255) products - id - name - price categories_products - categories_id - products_id

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  • Argument constraints in RhinoMock methods

    - by Khash
    I am mocking a repository that should have 1 entity in it for the test scenario. The repository has to return this entity based on a known id and return nothing when other ids are passed in. I have tried doing something like this: _myRepository.Expect(item => item.Find(knownId)).Return(knownEntity); _myRepository.Expect(item => item.Find(Arg<Guid>.Is.Anything)).Return(null); It seems however the second line is overriding the first and the repository always returns null. I don't want to mock all the different possible IDs asked (they could go up to hundreds) when the test scenario is only concerned with the value of one Id.

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  • Generic Constraints And Type Parameters Mess

    - by Dummy01
    Hi everyone, I have the following base abstract class defined as: public abstract class BaseObject<T> : IComparable, IComparable<T>, IEquatable<T> {} I also have an interface defined as: public interface ICode<T> where T : struct { T Code { get; } } Now I want to derive a class that is inherited from BaseObject<T> and includes interface ICode<T>. I tried to define it like that: public class DerivedObject<T, U> : BaseObject<T>, ICode<U> where T : DerivedObject<T, U> where U : struct { public DerivedObject(U code) { Code = code; } // From BaseObject protected override int InstanceCompareTo(T obj) { return Code.CompareTo(obj.Code); } // From BaseObject protected override bool InstanceEquals(T obj) { return Code.Equals(obj.Code); } // From ICode U _Code; public U Code { get { return _Code; } protected set { _Code = value; } } } The only error that comes from the compiler is for Code.CompareTo(obj.Code) with the message: 'U' does not contain a definition for 'CompareTo' and no extension method 'CompareTo' accepting a first argument of type 'U' could be found. But U is a value type and should know CompareTo. Have you any idea what I am doing wrong, or if I do all wrong? My final aim is to derive classes such these: public class Account : DerivedObject<Account, int> public class ItemGroup : DerivedObject<ItemGroup, string> Big Thanks In Advance!

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  • Adding class constraints to typeclass instance

    - by BleuM937
    I'm trying to implement the Cantor Pairing Function, as an instance of a generic Pair typeclass, as so: module Pair (Pair, CantorPair) where -- Pair interface class Pair p where pi :: a -> a -> p a k :: p a -> a l :: p a -> a -- Wrapper for typing newtype CantorPair a = P { unP :: a } -- Assume two functions with signatures: cantorPair :: Integral a => a -> a -> CantorPair a cantorUnpair :: Integral a => CantorPair a -> (a, a) -- I need to somehow add an Integral a constraint to this instance, -- but I can't work out how to do it. instance Pair CantorPair where pi = cantorPair k = fst . cantorUnpair l = snd . cantorUnpair How can I add the appropriate Integral constraint to the instance? I have a vague feeling I might need to modify the Pair interface itself, but not sure how to go about this.

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  • mysql circular dependency in foreign key constraints

    - by Flavius
    Given the schema: What I need is having every user_identities.belongs_to reference an users.id. At the same time, every users has a primary_identity as shown in the picture. However when I try to add this reference with ON DELETE NO ACTION ON UPDATE NO ACTION, MySQL says #1452 - Cannot add or update a child row: a foreign key constraint fails (yap.#sql-a3b_1bf, CONSTRAINT #sql-a3b_1bf_ibfk_1 FOREIGN KEY (belongs_to) REFERENCES users (id) ON DELETE NO ACTION ON UPDATE NO ACTION) I suspect this is due to the circular dependency, but how could I solve it (and maintain referential integrity)?

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  • sql server db deployment script ignoring constraints etc until commit

    - by Daniel
    Hi all, I am planning on doing a database deployment script for sql server 2005. Currently we have a tool that will run all of the tables, foreign keys, indexes and then data, each of which is located in a separate file with a certain extension (eg. tab, .kci, .fky) and the tool just runs *.tab, *.kci, *.fky into the db etc. Could I possibly combine all of thse into one file and have them run ignoring referential integrity until they are all complete, I would turn it on before we started inserting test data. It is just unmanageable having to maintain 4 or 5 different types of scripts for one table. Are there any issues I should be aware of? Cheers

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  • Mathematica & J/Link: Memory Constraints?

    - by D-Bug
    I am doing a computing-intensive benchmark using Mathematica and its J/Link Java interface. The benchmark grinds to a halt if a memory footprint of about 320 MB is reached, since this seems to be the limit and the garbage collector needs more and more time and will eventually fail. The Mathematica function ReinstallJava takes the argument command line. I tried to do ReinstallJava[CommandLine -> "java -Xmx2000m ..."] but Mathematica seems to ignore the -Xmx option completely. How can I set the -Xmx memory option for my java program? Where does the limit of 320 MB come from? Any help would be greatly appreciated.

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  • Merging rows with uniqueness constraints

    - by Flambino
    I've got a little time-tracking web app (implemented in Rails 3.2.8 & MySQL). The app has several users who add their time to specific tasks, on a given date. The system is set up so a user can only have 1 time entry (i.e. row) per task per date. I.e. if you add time twice on the same task and date, it'll add time to the existing row, rather than create a new one. Now I'm looking to merge 2 tasks. In the simplest terms, merging task ID 2 into task ID 1 would take this time | user_id | task_id | date ------+----------+----------+----------- 10 | 1 | 1 | 2012-10-29 15 | 2 | 1 | 2012-10-29 10 | 1 | 2 | 2012-10-29 5 | 3 | 2 | 2012-10-29 and change it into this time | user_id | task_id | date ------+----------+----------+----------- 20 | 1 | 1 | 2012-10-29 <-- time values merged (summed) 15 | 2 | 1 | 2012-10-29 <-- no change 5 | 3 | 1 | 2012-10-29 <-- task_id changed (no merging necessary) I.e. merge by summing the time values, where the given user_id/date/task combo would conflict. I figure I can use a unique constraint to do a ON DUPLICATE KEY UPDATE ... if I do an insert for every task_id=2 entry. But that seems pretty inelegant. I've also tried to figure a way to first update all the rows in task 1 with the summed-up times, but I can't quite figure that one out. Any ideas?

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  • What language/framework (technology) to use for website (flash games portal)

    - by cripox
    Hello, I know there are a lot of similar questions on the net, but because I am a newbie in web development I didn't find the solution for my specific problem. I am planing on creating a flash games portal from scratch. It is a big chance that there will be big traffic from the beginning (millions of pageviews). I want to reduce the server costs as much as possible but in the same time to not be tide to an expensive contract as there is a chance that the project will not be as successfully as I want and in that case the money would be very little. The question is : what technology to use? I don't know any web dev technology yet so it doesn't matter what I will learn. My web dev experience is a little php 8 years ago, and from then I programmed in C++ / Java- game and mobile development. I like Java and C syntax and language very much and I tend to dislike dynamic typing or non robust scripting (like php)- but I can get along if these are the best choices. The candidates are now: - Grails (my best for now) Ruby on Rails Cake PHP Other technologies (Google App Engine, Python/Django etc...) I was considering at first using pure C and compiling the web app in the server- just to squeeze more from the servers, but soon I understand that this is overkill. Next my eyes came on Ruby - as there is a lot of buzz for it's easiness of use. Next I discovered Grails and looked at Java because it is said that it is "faster". But I don't know what this "Faster" really means on my needs, so here comes the first question: 1) What will be my biggest consumption on the server, other than bandwidth, for a lot of flash content requests? Is it memory? I heard that Java needs a lot of memory, but is faster. Is it CPU? I am planning to take some daily VPS.NET nodes at first, to see if there is a demand, and if the "spike" is permanent to move to a dedicated server (serverloft.com has some good offers), else to remain with less nodes. I was also considering developing in Google App Engine- cheap or free hosting to use at first - so I can test my assumption- and also very easy to use (no need for sys administration) but the costs became high if used more ( 3 million games played / month .. x mb/ each). And the issue with Google is that it looks me in this technology. My other concern is scalability (not only for traffic/users, but as adding functionality) My plans are to release a functional site in just 4 weeks (just the basics frontend and some quick basic backend - so I can be able to modify some things and add games manually) - but then to raise it and add more things to it. I am planning to take a little different approach than other portals so I need to write it from scratch (a script will not do). 2) Will Grails take much more resources than RoR or Php server wise? I heard that making it on Java stack will be hardware expensive and is overkill if you don't make a bank application. My application will not be very complex (I hope and i will try to) but will have a lot of traffic. I also took in account using CDN for files, but the cheapest CDN found was 5c/GB (vps.net) and the cost per gb on serverloft (http://www.serverloft.com/dedizierte-server/server-details.php?products=4) is only 1.79 cents/GB and comes with the other resources either. I am new to this domain (web). I am learning the ropes and searching on the web for ~half of year but don't have any really practical experience, so I know that I must have some naive thinking and other issues that i don't know from now, so please give me any advice you want regarding anything, not just the specific questions asked. And thank you so much for such great community!

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