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• Complex sorting on MySQL database

  - by ChrisR

  I'm facing the following situation. We've got an CMS with an entity with translations. These translations are stored in a different table with a one-to-many relationship. For example newsarticles and newsarticle_translations. The amount of available languages is dynamically determined by the same CMS. When entering a new newsarticle the editor is required to enter at least one translation, which one of the available languages he chooses is up to him. In the newsarticle overview in our CMS we would like to show a column with the (translated) article title, but since none of the languages are mandatory (one of them is mandatory but i don't know which one) i don't really know how to construct my mysql query to select a title for each newsarticle, regardless of the entered language. And to make it all a little harder, our manager asked for the possibilty to also be able to sort on title, so fetching the translations in a separate query is ruled out as far as i know. Anyone has an idea on how to solve this in the most efficient way? Here are my table schema's it it might help > desc news; +-----------------+----------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+----------------+------+-----+-------------------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | category_id | int(1) | YES | | NULL | | | created | timestamp | NO | | CURRENT_TIMESTAMP | | | user_id | int(10) | YES | | NULL | | +-----------------+----------------+------+-----+-------------------+----------------+ > desc news_translations; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | enabled | tinyint(1) | NO | | 0 | | | news_id | int(1) unsigned | NO | | NULL | | | title | varchar(255) | NO | | | | | summary | text | YES | | NULL | | | body | text | NO | | NULL | | | language | varchar(2) | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ PS: i've though about subqueries and coalesce() solutions but those seem rather dirty tricks, wondering if something better is know that i'm not thinking of?

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• Stored procedure for generic MERGE

  - by GilliVilla

  I have a set of 10 tables in a database (DB1). And there are 10 tables in another database (DB2) with exact same schema on the same SQL Server 2008 R2 database server machine. The 10 tables in DB1 are frequently updated with data. I intend to write a stored procedure that would run once every day for synchronizing the 10 tables in DB1 with DB2. The stored procedure would make use of the MERGE statement. Now, my aim is to make this as generic and parametrized as possible. That is, accommodate for more tables down the line... and accommodate different source and target DB names. Definitely no hard coding is intended. This is my algorithm so far: Have the database names as parameters Have the first query within the stored procedure... result in giving the names of the 10 tables from a lookup table (this can be 10, 20 or whatever) Have a generic MERGE statement that does the sync for each of the above set of tables (based on primary key?) This is where I need more inputs on. What is the best way to achieve this stored procedure? SQL syntax would be helpful.

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• Index question: Select * with WHERE clause. Where and how to create index

  - by Mestika

  Hi, I’m working on optimizing some of my queries and I have a query that states: select * from SC where c_id ="+c_id” The schema of ** SC** looks like this: SC ( c_id int not null, date_start date not null, date_stop date not null, r_t_id int not null, nt int, t_p decimal, PRIMARY KEY (c_id, r_t_id, date_start, date_stop)); My immediate bid on how the index should be created is a covering index in this order: INDEX(c_id, date_start, date_stop, nt, r_t_id, t_p) The reason for this order I base on: The WHERE clause selects from c_id thus making it the first sorting order. Next, the date_start and date_stop to specify a sort of “range” to be defined in these parameters Next, nt because it will select the nt Next the r_t_id because it is a ID for a specific type of my r_t table And last the t_p because it is just a information. I don’t know if it is at all necessary to order it in a specific way when it is a SELECT ALL statement. I should say, that the SC is not the biggest table. I can say how many rows it contains but a estimate could be between <10 and 1000. The next thing to add is, that the SC, in different queries, inserts the data into the SC, and I know that indexes on tables which have insertions can be cost ineffective, but can I somehow create a golden middle way to effective this performance. Don't know if it makes a different but I'm using IBM DB2 version 9.7 database Sincerely Mestika

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• [Concept] How does unlink() find the file to delete?

  - by Prasad

  My app has a 'Photo' field to store URL. It uses sfWidgetFormInputFileEditable for the widget schema. To delete the old image when a new image is uploaded, I use unlink before setting the value in the over-ridden setter and it works!!! if (file_exists($this->_get('photo'))) unlink($this->_get('photo')); Photos are stored in uploads/photos and when saving 'Photo' only the file name xxx-yyy.zzz is saved (and not the full path). However, I wish to know how symfony/php knows the full path of the file to be deleted? Part 2: I am using sfThumbnailPlugin to generate thumbnails. So the actual code looks like this: public function setPhoto($value) { if(!empty($value)) { Contact::generateThumbnail($value); // delete current Photo & create thumbnail $this->_set('photo',$value); // setting new value after deleting old one } } public function generateThumbnail($value) { $uploadDir = sfConfig::get('app_photo_upload'); // path to upload folder if (file_exists($this->_get('photo'))) { unlink($this->_get('photo')); // delete full-size image // path to thumbnail $thumbpath = $uploadDir.'/thumbnails/'.$this->get('photo'); // read a blog, tried setting dir manually, doesn't work :( //chdir('/thumbnails/'); // tried closing the file too, doesn't work! :( //fclose($thumbpath) or die("can't close file"); //unlink($this->_get('photo')); // doesn't work; no error :( unlink($thumbpath); // doesn't work, no error :( } $thumbnail = new sfThumbnail(150, 150); $thumbnail->loadFile($uploadDir.'/'.$value); $thumbnail->save($uploadDir.'/thumbnails/'.$value, 'image/png'); } Why can't the thumbnail be deleted using unlink()? is the sequence of ops incorrect? Is it because the old thumbnail is displayed in the sfWidgetFormInputFileEditable widget? I've spent hours trying to figure this out, but unable to nail down the real cause. Thanks in advance.

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• How to delete ProgIDs from other user accounts when uninstalling from Windows?

  - by Mordachai

  I've been investigating "how should a modern windows c++ application register its file types" with Windows (see http://stackoverflow.com/questions/2828637/c-how-do-i-correctly-register-and-unregister-file-type-associations-for-our-ap). And having combed through the various MSDN articles on the subject, the summary appears to be as follows: The installer (elevated) should register the global ProgID HKLM\Software\Classes\my-app.my-doc[.version] (e.g. HKLM\Software\Classes\TextPad.text) The installer also configures default associations for its document types (e.g. .myext) and points this to the aforementioned global ProgID in HKLM. NOTE: a user interface should be provided here to allow the user to either accept all default associations, or to customize which associations should be set. The application, running standard (unelevated), should provide a UI for allowing the current user to set their personal associations as is available in the installer, except that these associations are stored in HKCU\Software\Classes (per user, not per machine). The UN-installer is then responsible for deleting all registered ProgIDs (but should leave the actual file associations alone, as Windows is smart enough to handle associations pointing to missing ProgIDs, and this is the specified desired behavior by MSDN). So that schema sounds reasonable to me, except when I consider #4: How does an uninstaller, running elevated for a given user account, delete any per-user ProgIDs created in step #3 for other users? As I understand things, even in elevated mode, an uninstaller cannot go into another user's registry hive and delete items? Or can it? Does it have to load each given user hive first? What are the rules here? Thanks for any insight you might have to offer! EDIT: See below for the solution (My question was founded in confusion)

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• c++ and visual studio 08, how to develop the following web extracting application. folloow up of las

  - by user287745

  the purpose is to use c++ in a useful way. i have just started programming and have made a few small applications in c and c#. my understanding is that programming for web and thing related to web is now a days a very easy task. please note this is for personnel learning not for rent a coder or any money making. an application which can run on any windows platform even win98. the application should start automatically at a scheduled time and do the following. connect to a site which displays stock prices summary (high low current open ). captures the data (excluding the other things in the site) and saves it to disk ( a sql database) please note:- internet connection is assumed to be there always. do not want to know how to make database schema or database. the stock exchange has no law prohibiting the use of the data provided on its site, but i do not want to mention the name in case i am wrong, but its for personnel private use only. the data of summary of pricing is arranged in a table such that when copied pasted to ms excel it automatically forms a table. guidance needed thank u.

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• Warehouse Attributes model

  - by Orapps

  i am giving a training project for building a schema the following is the question all i would like to ask you guys is i am not sure what attributes would come in the table please see the problem below... create one new company and attach 10 attributes to the company. the company has two warehouses one in Torrance and another in Costa mesa. each warehouse should have 10 attributes. the company sells 100 products and services. each product and services should have 10 attributes. the company received orders. the orders should have HEADERS and Lines (am not sure what these are). each headers and lin should have 10 attributes. there should be a table for quantity on hand. the quantity on hand will increase once the warehouse receives good. please i only want some hints or clues on what attributes would generally come in this highlighted tables. thanks for help in advance guys....

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• Login fails when recreating database with Code First

  - by Mun

  I'm using ASP.NET Entity Framework's Code First to create my database from the model, and the login seems to fail when the database needs to be recreated after the model changes. In Global.asax, I've got the following: protected void Application_Start() { Database.SetInitializer(new DropCreateDatabaseIfModelChanges<EntriesContext>()); // ... } In my controller, I've got the following: public ActionResult Index() { // This is just to force the database to be created var context = new EntriesContext(); var all = (from e in context.Entries select e).ToList(); } When the database doesn't exist, it is created with no problems. However, when I make a change to the model, rebuild and refresh, I get the following error: Login failed for user 'sa'. My connection string looks like this: <add name="EntriesContext" connectionString="Server=(LOCAL);Database=MyDB;User Id=sa;Password=password" providerName="System.Data.SqlClient" /> The login definitely works as I can connect to the server and the database from Management Studio using these credentials. If I delete the database manually, everything works correctly and the database is recreated as expected with the schema reflecting the changes made to the model. It seems like either the password or access to the database is being lost. Is there something else I need to do to get this working?

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• How to speed up a slow UPDATE query

  - by Mike Christensen

  I have the following UPDATE query: UPDATE Indexer.Pages SET LastError=NULL where LastError is not null; Right now, this query takes about 93 minutes to complete. I'd like to find ways to make this a bit faster. The Indexer.Pages table has around 506,000 rows, and about 490,000 of them contain a value for LastError, so I doubt I can take advantage of any indexes here. The table (when uncompressed) has about 46 gigs of data in it, however the majority of that data is in a text field called html. I believe simply loading and unloading that many pages is causing the slowdown. One idea would be to make a new table with just the Id and the html field, and keep Indexer.Pages as small as possible. However, testing this theory would be a decent amount of work since I actually don't have the hard disk space to create a copy of the table. I'd have to copy it over to another machine, drop the table, then copy the data back which would probably take all evening. Ideas? I'm using Postgres 9.0.0. UPDATE: Here's the schema: CREATE TABLE indexer.pages ( id uuid NOT NULL, url character varying(1024) NOT NULL, firstcrawled timestamp with time zone NOT NULL, lastcrawled timestamp with time zone NOT NULL, recipeid uuid, html text NOT NULL, lasterror character varying(1024), missingings smallint, CONSTRAINT pages_pkey PRIMARY KEY (id ), CONSTRAINT indexer_pages_uniqueurl UNIQUE (url ) ); I also have two indexes: CREATE INDEX idx_indexer_pages_missingings ON indexer.pages USING btree (missingings ) WHERE missingings > 0; and CREATE INDEX idx_indexer_pages_null ON indexer.pages USING btree (recipeid ) WHERE NULL::boolean; There are no triggers on this table, and there is one other table that has a FK constraint on Pages.PageId.

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• Checking if user owns file before deleting it

  - by Martin Hoe

  I'm building an API for my site that allows users to delete the files they upload. Obviously, I want to check if the user owns that file before they delete it through the API. I have a files table and a users table, here's the schema: f_id, s_id, u_id, name, size, uploaded u_id, username, password, email, activated, activation_code u_id is a foreign key. The u_id field in the files table points to the u_id in the users table. Given the users username, I want to find the users u_id, and then check if they own the file through the file ID (f_id). I wrote this SQL: $sql = 'SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f_id = ? AND u.u_id = ? LIMIT 1'; I'm assuming that'd work if I was given the users u_id in the API request, but alas I'm given only their username. How can I modify that SQL to find their user ID and use that? Thanks. Edit: Alright I've got this query but it's always returning an empty result set even though both the file ID and username exist. SELECT u.username FROM `users` u JOIN `files` f ON u.u_id = f.u_id WHERE f.f_id = ? AND u.username = ? LIMIT 1

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• Ruby on Rails How do I access variables of a model inside itself like in this example?

  - by banditKing

  I have a Model like so: # == Schema Information # # Table name: s3_files # # id :integer not null, primary key # owner :string(255) # notes :text # created_at :datetime not null # updated_at :datetime not null # last_accessed_by_user :string(255) # last_accessed_time_stamp :datetime # upload_file_name :string(255) # upload_content_type :string(255) # upload_file_size :integer # upload_updated_at :datetime # class S3File < ActiveRecord::Base #PaperClip methods attr_accessible :upload attr_accessor :owner Paperclip.interpolates :prefix do |attachment, style| I WOULD LIKE TO ACCESS VARIABLE= owner HERE- HOW TO DO THAT? end has_attached_file( :upload, :path => ":prefix/:basename.:extension", :storage => :s3, :s3_credentials => {:access_key_id => "ZXXX", :secret_access_key => "XXX"}, :bucket => "XXX" ) #Used to connect to users through the join table has_many :user_resource_relationships has_many :users, :through => :user_resource_relationships end Im setting this variable in the controller like so: # POST /s3_files # POST /s3_files.json def create @s3_file = S3File.new(params[:s3_file]) @s3_file.owner = current_user.email respond_to do |format| if @s3_file.save format.html { redirect_to @s3_file, notice: 'S3 file was successfully created.' } format.json { render json: @s3_file, status: :created, location: @s3_file } else format.html { render action: "new" } format.json { render json: @s3_file.errors, status: :unprocessable_entity } end end end Thanks, any help would be appreciated.

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• :include and table aliasing

  - by dondo

  I'm suffering from a variant of the problem described here: ActiveRecord assigns table aliases for association joins fairly unpredictably. The first association to a given table keeps the table name. Further joins with associations to that table use aliases including the association names in the path... but it is common for app developers not to know about [other] joins at coding time. In my case I'm being bitten by a toxic mix of has_many and :include. Many tables in my schema have a state column, and the has_many wants to specify conditions on that column: has_many :foo, :conditions => {:state => 1}. However, since the state column appears in many tables, I disambiguate by explicitly specifying the table name: has_many :foo, :conditions => "this_table.state = 1". This has worked fine until now, when for efficiency I want to add an :include to preload a fairly deep tree of data. This causes the table to be aliased inconsistently in different code paths. My reading of the tickets referenced above is that this problem is not and will not be fixed in Rails 2.x. However, I don't see any way to apply the suggested workaround (to specify the aliased table name explicitly in the query). I'm happy to specify the table alias explicitly in the has_many statement, but I don't see any way to do so. As such, the workaround doesn't appear applicable to this situation (nor, I presume, in many 'named_scope' scenarios). Is there a viable workaround?

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• calculating change (over a period) for a dated field

  - by morpheous

  I have two tables with the following schema: CREATE TABLE sales_data ( sales_time date NOT NULL, product_id integer NOT NULL, sales_amt double NOT NULL ); CREATE TABLE date_dimension ( id integer NOT NULL, datestamp date NOT NULL, day_part integer NOT NULL, week_part integer NOT NULL, month_part integer NOT NULL, qtr_part integer NOT NULL, year_part integer NOT NULL, ); I want to write two types of queries that will allow me to calculate: period on period change (e.g. week on week change) change in period on period change (e.g. change in week on week change) I would prefer to write this in ANSI SQL, since I dont want to be tied to any particular db. [Edit] In light of some of the comments, if I have to be tied to a single database (in terms of SQL dialect), it will have to be PostgreSQL The queries I want to write are of the form (pseudo SQL of course): Query Type 1 (Period on Period Change) ======================================= a). select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as week_on_week_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) b). select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as month_on_month_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) Query Type 2 (Change in Period on Period Change) ================================================= a). select product_id, ((a2.week_on_week_change - a1.week_on_week_change)/a1.week_on_week_change) as change_on_week_on_week_change from (select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as week_on_week_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) as a1), (select product_id, ((sd2.sales_amt - sd1.sales_amt)/sd1.sales_amt) as week_on_week_change from sales_data sd1, sales_data sd2, date_dimension dd where {SOME CRITERIA) as a2) WHERE {SOME OTHER CRITERIA}

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• Attribute value nil

  - by mridula

  Can someone tell me why is this happening? I have created a social networking website using Ruby on Rails. This is my first time programming with RoR. I have a model named "Friendship" which contains an attribute "blocked" to indicate whether the user has blocked another user. When I run the following in IRB - friendship = u.friendships.where(:friend_id => 22).first IRB gives me - Friendship Load (0.6ms) SELECT `friendships`.* FROM `friendships` WHERE `friendships`.`user_id` = 17 AND `friendships`.`friend_id` = 22 LIMIT 1 => #<Friendship id: 33, user_id: 17, friend_id: 22, created_at: "2012-04-07 10:29:49", updated_at: "2012-04-07 10:29:49", blocked: 1> As u can see, the "blocked" attribute has value '1'. But when I run the following 1.9.2-p290 :030 > friendship.blocked => nil - it says, the value of blocked is 'nil' and not '1'. Why is this happening? This could be a very silly mistake but I am new to RoR, so kindly help me! I initially didn't include the accessor method for 'blocked'.. I tried that, and still its giving the same result.. Following is the Friendship model.. class Friendship < ActiveRecord::Base belongs_to :friend, :class_name => "User" validates_uniqueness_of :friend_id , :scope => :user_id attr_accessor :blocked attr_accessible :blocked end Here is the schema of the table: 1.9.2-p290 :009 > friendship.class => Friendship(id: integer, user_id: integer, friend_id: integer, created_at: datetime, updated_at: datetime, blocked: integer)

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• Is it possible to modify the value of a record's primary key in Oracle when child records exist?

  - by Chris Farmer

  I have some Oracle tables that represent a parent-child relationship. They look something like this: create table Parent ( parent_id varchar2(20) not null primary key ); create table Child ( child_id number not null primary key, parent_id varchar2(20) not null, constraint fk_parent_id foreign key (parent_id) references Parent (parent_id) ); This is a live database and its schema was designed long ago under the assumption that the parent_id field would be static and unchanging for a given record. Now the rules have changed and we really would like to change the value of parent_id for some records. For example, I have these records: Parent: parent_id --------- ABC123 Child: child_id parent_id -------- --------- 1 ABC123 2 ABC123 And I want to modify ABC123 in these records in both tables to something else. It's my understanding that one cannot write an Oracle update statement that will update both parent and child tables simultaneously, and given the FK constraint, I'm not sure how best to update my database. I am currently disabling the fk_parent_id constraint, updating each table independently, and then enabling the constraint. Is there a better, single-step way to update this content?

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• MySQL Join Question

  - by rbaker86

  Hi i'm struggling to write a particular MySQL Join Query. I have a table containing product data, each product can belong to multiple categories. This m:m relationship is satisfied using a link table. For this particular query I wish to retrieve all products belonging to a given category, but with each product record, I also want to return the other categories that product belongs to. Ideally I would like to achieve this using an Inner Join on the categories table, rather than performing an additional query for each product record, which would be quite inefficient. My simplifed schema is designed roughly as follows: products table: product_id, name, title, description, is_active, date_added, publish_date, etc.... categories table: category_id, name, title, description, etc... product_category table: product_id, category_id I have written the following query, which allows me to retrieve all the products belonging to the specified category_id. However, i'm really struggling to work out how to retrieve the other categories a product belongs to. SELECT p.product_id, p.name, p.title, p.description FROM prod_products AS p LEFT JOIN prod_product_category AS pc ON pc.product_id = p.product_id WHERE pc.category_id = $category_id AND UNIX_TIMESTAMP(p.publish_date) < UNIX_TIMESTAMP() AND p.is_active = 1 ORDER BY p.name ASC I'd be happy just retrieving the category id's releated to each returned product row, as I will have all category data stored in an object, and my application code can take care of the rest. Many thanks, Richard

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• What is the fastest way to insert 100 000 records from one database to another?

  - by Pentium10

  I have a mobile application. My client has a large data set ~100.000 records. It's updated frequently. When we sync we need to copy from one database to another. I have attached the second database to the main, and run an insert into table select * from sync.table. This is extremely slow, it takes about 10 minutes I think. I noticed that the journal file gets increased step by step. How can I speed this up? EDITED 1 I have indexes off, and I have journal off. Using insert into table select * from sync.table it still takes 10 minutes. EDITED 2 If I run a query like select id,invitem,invid,cost from inventory where itemtype = 1 order by invitem limit 50 it takes 15-20 seconds. The table schema is: CREATE TABLE inventory ('id' INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 'serverid' INTEGER NOT NULL DEFAULT 0, 'itemtype' INTEGER NOT NULL DEFAULT 0, 'invitem' VARCHAR, 'instock' FLOAT NOT NULL DEFAULT 0, 'cost' FLOAT NOT NULL DEFAULT 0, 'invid' VARCHAR, 'categoryid' INTEGER DEFAULT 0, 'pdacategoryid' INTEGER DEFAULT 0, 'notes' VARCHAR, 'threshold' INTEGER NOT NULL DEFAULT 0, 'ordered' INTEGER NOT NULL DEFAULT 0, 'supplier' VARCHAR, 'markup' FLOAT NOT NULL DEFAULT 0, 'taxfree' INTEGER NOT NULL DEFAULT 0, 'dirty' INTEGER NOT NULL DEFAULT 1, 'username' VARCHAR, 'version' INTEGER NOT NULL DEFAULT 15 ) Indexes are created like CREATE INDEX idx_inventory_categoryid ON inventory (pdacategoryid); CREATE INDEX idx_inventory_invitem ON inventory (invitem); CREATE INDEX idx_inventory_itemtype ON inventory (itemtype); I am wondering, the insert into ... select * from isn't the fastest built-in way to do massive data copy? EDITED 3 SQLite is serverless, so please stop voting a particular answer, because that is not the answer I'm sure.

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• What am I doing wrong with my ItemsControl & databinding?

  - by Joel

  I'm reworking my simple hex editor to practice using what I've recently learned about data binding in WPF. I'm not sure what I'm doing wrong here. As I understand it, for each byte in the collection "backend" (inherits from ObservableCollection), my ItemsControl should apply the DataTemplate under resources. This template is just a textbox with a binding to a value converter. So I'm expecting to see a row of textboxes, each containing a string representation of one byte. When I use this XAML, all I get is a single line of uneditable text, which as far as I can tell doesn't use a textbox. What am I doing wrong? I've pasted my XAML in below, with the irrelevant parts (Menu declaration, schema, etc) removed. <Window ...> <Window.Resources> <local:Backend x:Key="backend" /> <local:ByteConverter x:Key="byteConverter" /> <DataTemplate DataType="byte"> <TextBox Text="{Binding Converter={StaticResource byteConverter}}" /> </DataTemplate> </Window.Resources> <StackPanel> <ItemsControl ItemsSource="{Binding Source={StaticResource backend}}"> <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <WrapPanel /> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> </ItemsControl> </StackPanel> </Window>

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• EF code first error "The specified index already exists. [ IX_Id ]" for object tree

  - by PascalN

  Using EF code first 4.3 I'm trying to model an object tree with a required-required relationships and a required-optional relationships. Here is a simple representation of those classes public class Top { public int Id { get; set; } public virtual Middle Middle { get; set; } } public class Middle { public int Id { get; set; } public virtual Child Child { get; set; } } public class Child { public int Id { get; set; } } Here is the OnModelCreating code modelBuilder.Entity<Top>().HasRequired(t => t.Middle).WithRequiredPrincipal().WillCascadeOnDelete(); modelBuilder.Entity<Middle>().HasRequired(t => t.Child).WithOptional().WillCascadeOnDelete(); This produces the error "The specified index already exists. [ IX_Id ]" on SQLCE After checking the db schema, both model binder fluent API configuration lines create an index IX_Id on the table Middles. Does anyone know how to work around that problem? Is there a way to set the index name? Thank you! Pascal

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• update record only works when there is no auto_increment

  - by every_answer_gets_a_point

  i am accessing a mysql table through an odbc connection in excel here is how i am updating the table: With rs .AddNew ' create a new record ' add values to each field in the record .Fields("datapath") = dpath .Fields("analysistime") = atime .Fields("reporttime") = rtime .Fields("lastcalib") = lcalib .Fields("analystname") = aname .Fields("reportname") = rname .Fields("batchstate") = "bstate" .Fields("instrument") = "NA" .Update ' stores the new record End With when the schema of the table is this, updating it works: create table batchinfo(datapath text,analysistime text,reporttime text,lastcalib text,analystname text, reportname text, batchstate text, instrument text); but when i have auto_increment in there it does not work: CREATE TABLE batchinfo ( rowid int(11) NOT NULL AUTO_INCREMENT, datapath text, analysistime text, reporttime text, lastcalib text, analystname text, reportname text, batchstate text, instrument text, PRIMARY KEY (rowid) ) ENGINE=InnoDB AUTO_INCREMENT=67 DEFAULT CHARSET=latin1 has anyone experienced a problem like this where updating does not work when there is an auto_increment field involved? connection string: Private Sub ConnectDB() Set oConn = New ADODB.Connection oConn.Open "DRIVER={MySQL ODBC 5.1 Driver};" & _ "SERVER=localhost;" & _ "DATABASE=employees;" & _ "USER=root;" & _ "PASSWORD=pas;" & _ "Option=3" End Sub also here's the rs.open: rs.Open "batchinfo", oConn, adOpenKeyset, adLockOptimistic, adCmdTable

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• Is this a good way to generically deserialize objects?

  - by Damien Wildfire

  I have a stream onto which serialized objects representing messages are dumped periodically. The objects are one of a very limited number of types, and other than the actual sequence of bytes that arrives, I have no way of knowing what type of message it is. I would like to simply try to deserialize it as an object of a particular type, and if an exception is thrown, try again with the next type. I have an interface that looks like this: public interface IMessageHandler<T> where T : class, IMessage { T Handle(string message); } // elsewhere: // (These are all xsd.exe-generated classes from an XML schema.) public class AppleMessage : IMessage { ... } public class BananaMessage : IMessage { ... } public class CoconutMessage : IMessage { ... } Then I wrote a GenericHandler<T> that looks like this: public class GenericHandler<T> : IMessageHandler<T> where T: class, IMessage { public class MessageHandler : IMessageHandler { T IMessageHandler.Handle(string message) { T result = default(T); try { // This utility method tries to deserialize the object with an // XmlSerializer as if it were an object of type T. result = Utils.SerializationHelper.Deserialize<T>(message); } catch (InvalidCastException e) { result = default(T); } return result; } } } Two questions: Using my GenericHandler<T> (or something similar to it), I'd now like to populate a collection with handlers that each handle a different type. Then I want to invoke each handler's Handle method on a particular message to see if it can be deserialized. If I get a null result, move onto the next handler; otherwise, the message has been deserialized. Can this be done? Is there a better way to deserialize data of unknown (but restricted) type?

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• Website badge system

  - by linkyndy

  I am currently working on a widget-based website, built entirely on user socialization. Since a reputation system pays off for attracting users, I decided to implement one of these. Now, I would like to hear some solutions on how should this be implemented the right way (take, for example, Foursquare's badge system). Basically, I need to be able to do the following: have a badges table, where I can add, edit and delete badges; be able to enable and disable a badge; be able to introduce a new badge, but without writing new code - simply give some parameters to the add badge form regarding what should be followed in order for a user to receive a badge; be able to give badges in real time - meaning that whenever a user accomplishes whatever it needs to receive a badge, the system should know immediately to give the badge to that user; also, the system should not be overloaded with "badge listeners" - I believe interrogating each user request with every badge requirements is time consuming; These being said, I would like to hear your opinions on how to implement the right way a badge system (logic, database schema, methods etc.) Thank you very much!

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• Optimize SQL query (Facebook-like application)

  - by fabriciols

  My application is similar to Facebook, and I'm trying to optimize the query that get user records. The user records are that he as src ou dst. The src is in usermuralentry directly, the dst list are in usermuralentry_user. So, a entry can have one src and many dst. I have those tables: mysql> desc usermuralentry ; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | user_src_id | int(11) | NO | MUL | NULL | | | private | tinyint(1) | NO | | NULL | | | content | longtext | NO | | NULL | | | date | datetime | NO | | NULL | | | last_update | datetime | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ 10 rows in set (0.10 sec) mysql> desc usermuralentry_user ; +-------------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------------+---------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | usermuralentry_id | int(11) | NO | MUL | NULL | | | userinfo_id | int(11) | NO | MUL | NULL | | +-------------------+---------+------+-----+---------+----------------+ 3 rows in set (0.00 sec) And the following query to retrieve information from two users. mysql> explain SELECT * FROM usermuralentry AS a , usermuralentry_user AS b WHERE a.user_src_id IN ( 1, 2 ) OR ( a.id = b.usermuralentry_id AND b.userinfo_id IN ( 1, 2 ) ); +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ | 1 | SIMPLE | b | ALL | usermuralentry_id,usermuralentry_user_bcd7114e,usermuralentry_user_6b192ca7 | NULL | NULL | NULL | 147188 | | | 1 | SIMPLE | a | ALL | PRIMARY | NULL | NULL | NULL | 1371289 | Range checked for each record (index map: 0x1) | +----+-------------+-------+------+-------------------------------------------------------------------------------------------+------+---------+------+---------+------------------------------------------------+ 2 rows in set (0.00 sec) but it is taking A LOT of time... Some tips to optimize? Can the table schema be better in my application?

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• creating tables in ruby-on-rails 3 through migrations?

  - by fayer

  im trying to understand the process of creating tables in ruby-on-rails 3. i have read about migrations. so i am supposed to create tables by editing in the files in: Database Migrations/migrate/20100611214419_create_posts Database Migrations/migrate/20100611214419_create_categories but they were generated by: rails generate model Post name:string description:text rails generate model Category name:string description:text does this mean i have to use "rails generate model" command everytime i want to create a table? what if i create a migration file but want to add columns. do i create another migration file for adding those or do i edit the existing migration file directly? the guide told me to add a new one, but here is the part i dont understand. why would i add a new one? cause then the new state will be dependent of 2 migration files. in symfony i just edit a schema.yml file directly, there are no migration files with versioning and so on. im new to RoR and want to get the picture of creating tables. thanks

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• What is a good solution to log the deletion of a row in MySQL?

  - by hobodave

  Background I am currently logging deletion of rows from my tickets table at the application level. When a user deletes a ticket the following SQL is executed: INSERT INTO alert_log (user_id, priority, priorityName, timestamp, message) VALUES (9, 4, 'WARN', NOW(), "TICKET: David A. deleted ticket #6 from Foo"); Please do not offer schema suggestions for the alert_log table. Fields: user_id - User id of the logged in user performing the deletion priority - Always 4 priorityName - Always 'WARN' timestamp - Always NOW() message - Format: "[NAMESPACE]: [FullName] deleted ticket #[TicketId] from [CompanyName]" NAMESPACE - Always TICKET FullName - Full name of user identified by user_id above TicketId - Primary key ID of the ticket being deleted CompanyName - Ticket has a Company via tickets.company_id Situation/Questions Obviously this solution does not work if a ticket is deleted manually from the mysql command line client. However, now I need to. The issues I'm having are as follows: Should I use a PROCEDURE, FUNCTION, or TRIGGER? -- Analysis: TRIGGER - I don't think this will work because I can't pass parameters to it, and it would trigger when my application deleted the row too. PROCEDURE or FUNCTION - Not sure. Should I return the number of deleted rows? If so, that would require a FUNCTION right? How should I account for the absence of a logged in user? -- Possibilities: Using either a PROC or FUNC, require the invoker to pass in a valid user_id Require the user to pass in a string with the name Use the CURRENT_USER - meh Hard code the FullName to just be "Database Administrator" Could the name be an optional parameter? I'm rather green when it comes to sprocs. Assuming I went with the PROC/FUNC approach, is it possible to outright restrict regular DELETE calls to this table, yet still allow users to call this PROC/FUNC to do the deletion for them? Ideally the solution is usable by my application as well, so that my code is DRY.

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