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  • What's the best way to store sort order in SQL?

    - by Duracell
    The guys at the top want sort order to be customizable in our app. So I have a table that effectively defines the data type. What is the best way to store our sort order. If I just created a new column called 'Order' or something, every time I updated the order of one row I imagine I would have to update the order of every row to ensure posterity. Is there a better way to do it?

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  • B- trees, B+ trees difference

    - by dta
    In a B- tree you can store both keys and data in the internal/leaf nodes. But in a B+ tree you have to store the data in the leaf nodes only. Is there any advantage of doing the above in a B+ tree? Why not use B- trees instead of B+ trees everywhere? As intuitively they seem much faster. I mean why do you need to replicate the key(data) in a B+ tree?

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  • User account design and security...

    - by espinet
    Before I begin, I am using Ruby on Rails and the Devise gem for user authentication. Hi, I was doing some research about account security and I found a blog post about the topic awhile ago but I can no longer find it again. I read something about when making a login system you should have 1 model for User, this contains a user's username, encrypted password, and email. You should also have a model for a user's Account. This contains everything else. A User has an Account. I don't know if I'm explaining this correctly since I haven't seen the blog post for several months and I lost my bookmark. Could someone explain how and why I should or shouldn't do this. My application deals with money so I need to cover my bases with security. Thanks.

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  • RavenDB-Embedded Unstable In Cooperation With ASP .Net Web API Using 2-Tier Architecture

    - by Mohsen Alikhani
    My application is used RavenDB-Embedded Unstable 1.2.2127 that it's intracted with ASP .Net Web API in the separated assemblies. When I use "UseEmbeddedHttpServer = true" on the document store, first time I send a request to RavenDB, it executes properly but when I try for the second time my application displays Raven Studio. However, if UseEmbeddedServer setting be removed then my application will be running without any problems. My RavenDB is configured with the following codes in data tier : this.documentStore = new EmbeddableDocumentStore { ConnectionStringName = "RavenDB", UseEmbeddedHttpServer = true } and implementation of Web.config have these settings in the service tier : <connectionStrings> <add name="RavenDB" connectionString="~\App_Data\RavenDatabase" /> </connectionStrings> Is there a setting I missed?

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  • bidirectional habtm linking

    - by Alexey Poimtsev
    Hi, all. I have application with 2 groups of models - content based (news, questions) and "something" based (devices, applications etc). I need to link all models between groups - for example question may belongs to 3 different things - one application and 2 devices. The same - for news. From other side - i need to see all news articles and questions related to some application or device. Any idea how to develop this in rails? I have only one idea - mixins that will add methods content_id and thing_id to models and join table.

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  • How may I create an horizontal view from a tree table

    - by Giuseppe Alfieri
    I want to create a view for each tree for each customer of this 3 table structured in this way: Fields: db_attrib.name, db_attrib.name, db_attrib.name until the last db_tree.id_child = 0 Values: db_attrib_values.value where db_attrib.id = db_attrib_value.id_attrib and so on for each child And so on for each db_tree.id This is the link to sql fiddle with the prepared structure: http://sqlfiddle.com/#!9/21516

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  • Rails: translations for table's column.

    - by Andrew
    In rails application I have two models: Food and Drink. Both food and drink have a name, which has to be stored in two languages. How do I better realize translations for theese tables? First solution I realized was to replace name column with name_en and name_ru. Another solution is to encode with YAML hash like { :en => 'eng', :ru => 'rus' } and store yaml as a name. What would you recommend, assuming content is not static? Maybe there's good article?

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  • Mapping a ER model to Rails

    - by Thiago
    Hi there, I want to map the following ER schema to rails: I have an entity called "user" which has a self relationship called "has friend", which has an attribute called "status". In code, I would like to run: User.friends and it should return me an array of users, containing the users that I'm friend of. It shouldn't matter in which side of the relationship I am (i.e. whether I'm the friender or the friendee). Any thoughts?

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  • Tools to work with App Engine data dumps

    - by Thilo
    Using the bulkloader.py utility you can download all data from your application's Datastore. It is not obvious how the data is stored, however. From the looks of it, you get a SQLite file with all data in binary format in a single table: sqlite> .tables bulkloader_database_signature result sqlite> .schema result CREATE TABLE result ( id BLOB primary key, value BLOB not null, sort_key BLOB); Are there any tools to work with this data?

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  • Strategy for Offline/Online data synchronization

    - by Adi
    My requirement is I have server J2EE web application and client J2EE web application. Sometimes client can go offline. When client comes online he should be able to synchronize changes to and fro. Also I should be able to control which rows/tables need to be synchronized based on some filters/rules. Is there any existing Java frameworks for doing it? If I need to implement on my own, what are the different strategies that you can suggest? One solution in my mind is maintaining sql logs and executing same statements at other side during synchronization. Do you see any problems with this strategy?

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  • please help me to interpret the naive bayes result in weka..

    - by resmi
    Anybody please help me to interpret the following result generated in weka for classification using naive bayes.....Please explain clearly what is this Normal Distribution , Mean , StandardDev , WeightSum and Precision.Please help me.Am new in weka. ** Naive Bayes Classifier Class Normal: Prior probability = 0.5 1374195_at: Normal Distribution. Mean = 218.06 StandardDev = 6.0572 WeightSum = 3 Precision = 36.34333334 1373315_at: Normal Distribution. Mean = 1142.58 StandardDev = 21.1589 WeightSum = 3 Precision = 126.95333339999999

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  • How to make a mapped field inherited from a superclass transient in JPA?

    - by Russ Hayward
    I have a legacy schema that cannot be changed. I am using a base class for the common features and it contains an embedded object. There is a field that is normally mapped in the embedded object that needs to be in the persistence id for only one (of many) subclasses. I have made a new id class that includes it but then I get the error that the field is mapped twice. Here is some example code that is much simplified to maintain the sanity of the reader: @MappedSuperclass class BaseClass { @Embedded private Data data; } @Entity class SubClass extends BaseClass { @EmbeddedId private SubClassId id; } @Embeddable class Data { private int location; private String name; } @Embeddable class SubClassId { private int thingy; private int location; } I have tried @AttributeOverride but I can only get it to rename the field. I have tried to set it to updatable = false, insertable = false but this did not seem to work when used in the @AttributeOverride annotation. See answer below for the solution to this issue. I realise I could change the base class but I really do not want to split up the embedded object to separate the shared field as it would make the surrounding code more complex and require some ugly wrapping code. I could also redesign the whole system for this corner case but I would really rather not. I am using Hibernate as my JPA provider.

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  • Avoiding Duplicate Data in DB (for use with Rails)

    - by ants
    I have five tables that I am trying to get to work nicely together but may need some help. I have three main tables: accounts members and roles. With two join tables account_members and account_member_roles. The accounts and members table are joined by account_members (fk account_id and member_id) table. The other 2 tables are the problem (roles and account_member_roles). A member of an account can have more than one role and I have the account_member_roles (fk account_member_id and role_id) table joining the account_members join table and the roles table. That seems logical but can you have a relationship with a join table? What I'd like to be able to do is when creaeting an account, for instance, I would like @account.save to include the roles and update the account_member_roles table neatly ..... but through the account_members join table. I've tried ..... accept_nested_attributes_for :members, :account_member_roles in the account.rb but I get ..... ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection (Cannot modify association 'Account#account_member_roles' because the source reflection class 'AccountMemberRole' is associated to 'AccountMember' via :has_many.) upon trying to save a record. Any advice on how I should approach this? CIA -ants

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  • Concurency problem with Isolation - read-committed

    - by Ratn Deo--Dev
    I have to write a simple demo for amount withdrawl from a joint Bank amount .Andy and Jen holds a joint bank account with number 123 . Suppose they have 100$ in their account .Jen and Andy are operating their account at the same time and both are trying to withdraw 90$ at the time being .My transaction Isolation is set to read-committed and both are able to withdraw money leaving the balance to -(minus)80$ although I have constraint that balance should never be less than 0. I am using hibernate .Is versioning only way to solve this problem or I should go for another Isolation level ?

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  • how relate one table to another for future records

    - by Sinan
    I have a games table which holds the data about a game. Then another table which holds the data about news. So far so good. First I thought about creating a junction table for game_news so I could relate news to games. This way works as intended when the game exists. So whenever I insert a news I can relate it to a game using the junction table. However there are cases when there is news about game but the game isn't published and it doesn't exists. So my question would be; is there a way to relate these news to a particular game when the game record is created. What is the best way to do this? Any ideas?

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  • Data-related security Implementation

    - by devdude
    Using Shiro we have a great security framework embedded in our enterprise application running on GF. You define users, roles, permissions and we can control at any fine-grain level if a user can access the application, a certain page or even click a specific button. Is there a recipe or pattern, that allows on top of that, to restrict a user from seeing certain data ? Sample: You have a customer table for 3 factories (part of one company). An admin user can see all customer records, but the user at the local factory must not see any customer data of other factories (for whatever reason). Te security feature should be part of the role definition. Thanks for any input and ideas

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  • many-to-many query

    - by kofto4ka
    Hello, guys! I have a problem and I dont know what is better solution. Okay, I have 2 tables: posts(id, title), posts_tags(post_id, tag_id). I have next task: must select posts with tags ids for example 4, 10 and 11. Not exactly, post could have any other tags at the same time. So, how I could do it more optimized? Creating temporary table in each query? Or may be some kind of stored procedure? In the future, user could ask script to select posts with any count of tags (it could be 1 tag only or 10 at the same time) and I must be sure that method that I will choose would be the best method for my problem. Sorry for my english, thx for attention.

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  • search & replace on 3000 row, 25 column spreadsheet

    - by Deca
    I'm attempting to clean up data in this (old) spreadsheet and need to remove things like single and double quotes, HTML tags and so on. Trouble is, it's a 3000 row file with 25 columns and every spreadsheet app I've tried (NeoOffice, MS Excel, Apple Numbers) chokes on it. Hard. Any ideas on how else I can clean this thing up for import to MySQL? Clearly I could go through each record manually, row by row, but would like to avoid that if at all possible. Likewise, I could write a PHP script to handle it on import, but don't want to put the server into a death spiral either.

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  • MySQL slow query

    - by andrhamm
    SELECT items.item_id, items.category_id, items.title, items.description, items.quality, items.type, items.status, items.price, items.posted, items.modified, zip_code.state_prefix, zip_code.city, books.isbn13, books.isbn10, books.authors, books.publisher FROM ( ( items LEFT JOIN bookitems ON items.item_id = bookitems.item_id ) LEFT JOIN books ON books.isbn13 = bookitems.isbn13 ) LEFT JOIN zip_code ON zip_code.zip_code = items.item_zip WHERE items.rid = $rid` I am running this query to get the list of a user's items and their location. The zip_code table has over 40k records and this might be the issue. It currently takes up to 15 seconds to return a list of about 20 items! What can I do to make this query more efficient?

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