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• Is there a class like a Dictionary without a Value template? Is HashSet<T> the correct answer?

  - by myotherme

  I have 3 tables: Foos, Bars and FooBarConfirmations I want to have a in-memory list of FooBarConfirmations by their hash: FooID BarID Hash 1 1 1_1 2 1 2_1 1 2 1_2 2 2 2_2 What would be the best Class to use to store this type of structure in-memory, so that I can quickly check to see if a combination exists like so: list.Contains("1_2"); I can do this with Dictionary<string,anything>, but it "feels" wrong. HashSet looks like the right tool for the job, but does it use some form of hashing algorithm in the background to do the lookups efficiently?

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• Is this SQL select code following good practice?

  - by acidzombie24

  I am using sqlite and will port to mysql (5) later. I wanted to know if I am doing something I shouldnt be doing. I tried purposely to design so I'll compare to 0 instead of 1 (I changed hasApproved to NotApproved to do this, not a big deal and I haven't written any code). I was told I never need to write a subquery but I do here. My Votes table is just id, ip, postid (I don't think I can write that subquery as a join instead?) and that's pretty much all that is on my mind. Naming conventions I don't really care about since the tables are created via reflection and is all over the place. select id, name, body, upvotes, downvotes, (select 1 from UpVotes where IPAddr=? AND post=Post.id) as myup, (select 1 from DownVotes where IPAddr=@0 AND post=Post.id) as mydown from Post where flag = '0' limit ?, ?"

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• Rails always include (join) on initialize

  - by Seth

  Hello, I have a User model as illustrated below: class User < ActiveRecord belongs_to :college belongs_to :class_level end I want to ALWAYS join with those other two tables returning one simplified User object. How do I accomplish this in my User model. I'm aware that I can do this in another model: class Foo < ActiveRecord has_many :users, :include => [:college, :class_level] end But I want to do this in my User model, so Foo.users will either be eager loaded OR be joined already. Is there a way to create an initialize this in the User model?

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• How to get notified of changes on a read only table? (I.e., Price drop notifications.)

  - by mirthlab

  Let's say I have these tables/models: Product - id - last_updated_date - name - price User - id - name Wishlist - id - user_id - product_id The Product table has a few million records and is being updated automatically each night via a data import (inserting into a new table, dropping the old one). I basically have read-only access to that table/model. If a product is on a user's wishlist and the price drops, I'd like to be able to notify that user. What methods can be used to do this? I have a couple of ideas: Keep track of the Product.last_updated_date in the wishlist model and periodically poll the product table to see if it has been updated. This sounds like a horrible/non-scaleable solution. Some sort of Postgres View or Function that triggers when the Product table is updated? I'm new to postgres so I'm not yet sure if this is even possible. Something amazing that you will suggest that I haven't thought of :) Any help in the right direction is greatly appreciated!

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• Query to find all bars that sell three different beers at the same price

  - by Eternal Learner

  Query to find "All bars that sell three different beers at the same price?" My Tables are Sells(bar,beer,price) - bar - foreign Key.. Bars(name,addr) - name primary key. I thought of something like this but that dosent seem to work ... Select A.bar As bar , B.bar as bar From Sells AS A, Sells AS B Where A.bar = B.bar and A.beer <> B.beer Group By(A.beer) Having Count(Distinct A.beer) >= 2 Is this the correct SQL query ?

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• is it possible to write data to a collection in wpf?

  - by randyc

  Hello. In looking through samples I have seen a number of examples where it is possible to present data within a wpf applicaiton by binding to collections. However I was wondering is it possible to write to a collection from an applicaiton. Say for example i have 2 or more fields such as names and I wanted to have hte ability to add up to three names in my application ( all stored in memory). Will collections serve this purpose. In the past with asp.net I have done this by creating data tables and storing values on the fly or during the session. I am trying to learn WPF and I was wondering if collections work in the same fashion? If so could you please post an example or point me to references that show examples of this? Thank you in advance.

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• how can add an extra select in this query?

  - by BulgedSnowy

  i've three tables related. images: id | filename | filesize | ... nodes: image_id | tag_id tags: id | name And i'm using this query to search images containing x tags SELECT images.* FROM images INNER JOIN nodes ON images.id = nodes.image_id WHERE tag_id IN (SELECT tags.id FROM tags WHERE tags.tag IN ("tag1","tag2")) GROUP BY images.id HAVING COUNT(*)= 2 The problem is that i need to retrieve also all images contained by the retrieved image, and i need this in the same query. This the actual query wich search retrieve all tags contained by the image: SELECT tag FROM nodes JOIN tags ON nodes.tag_id = tags.id WHERE image_id = images.id and nodes.private = images.private ORDER BY tag How can i mix this two to have only one query?

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• Is there a best practice for maintaining history in a database?

  - by Pete

  I don't do database work that often so this is totally unfamiliar territory for me. I have a table with a bunch of records that users can update. However, I now want to keep a history of their changes just in case they want to rollback. Rollback in this case is not the db rollback but more like revert changes two weeks later when they realized that they made a mistake. The distinction being that I can't have a transaction do the job. Is the current practice to use a separate table, or just a flag in the current table? It's a small database, 5 tables each with < 6 columns, < 1000 rows total.

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• deleting a large number of rows from a table

  - by Azeem

  We have a requirement to delete rows in the order of millions from multiple tables as a batch job (note that we are not deleting all the rows, we are deleting based on a timestamp stored in an indexed column). Obviously a normal DELETE takes forever (because of logging, referential constraint checking etc.). I know in the LUW world, we have ALTER TABLE NOT LOGGED INITIALLY but I can't seem to find the an equivalent SQL statement for DB2 v8 z/OS. Any one has any ideas on how to do this really fast? Also, any ideas on how to avoid the referential checks when deleting the rows? Please let me know.

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• Dtaset holds a table called "Table", not the table I pass in?

  - by dotnetdev

  Hi, I have the code below: string SQL = "select * from " + TableName; using (DS = new DataSet()) using (SqlDataAdapter adapter = new SqlDataAdapter()) using (SqlConnection sqlconn = new SqlConnection(connectionStringBuilder.ToString())) using (SqlCommand objCommand = new SqlCommand(SQL, sqlconn)) { sqlconn.Open(); adapter.SelectCommand = objCommand; adapter.Fill(DS); } System.Windows.Forms.MessageBox.Show(DS.Tables[0].TableName); return DS; However, every time I run this code, the dataset (DS) is filled with one table called "Table". It does not represent the table name I pass in as the parameter TableName and this parameter does not get mutated so I don't know where the name Table comes from. I'd expect the table to be the same as the tableName parameter I pass in? Any idea why this is not so? Thanks

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• EntityFramework: using association or add property manualy

  - by dritterweg

  I'm starting to use Entity Framework. Let's say I have to Entity from my tables in DB. Here is the table schema Profiles ProfileId FirstName LastName Hobbies Id HobbyName OwnerId So one profile can have many hobbies. My Entity Framework: ProfileEntity ProfileId FirstName LastName Hobbies (collection of HobbyEntity) note: this created by the Association tool HobbyEntity Id HobbyName Owner (type of ProfileEntity) note: this created by the Association tool, for me this property is not important my question: should I use the "Association" tool to make the relationship between the two entities, which in result create a property of each entity (in ProfileEntity will create a HobbyEntity and vica versa) or should I not use the association and only add a scalar property manually such as List<HobbyEntity> in my ProfileEntity and OwnerId in HobbyEntity.

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• Core Data No Longer Updating Sqlite Schema

  - by nefsu

  I am using core data for my app and I never had any problems adding or removing columns until recently. But now even if I make changes to my xcdatamodel and generate new and updated entity h/m files, sqlite doesn't seem to be picking up the changes. I actually went over to the documents folder and inspected the create statement for the relevant tables in sqlite3 and I was able to confirm that the columns I added were missing. I removed and redeployed the app several times to no avail. Is it possible to do something to the app to make it disregard any schema changes being made through xcdatamodel? I guess another thing I should mention is I recently started putting my entire projects folder in CVS so I wonder if something got messed up in the checkin and check out process.

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• Multiple user database design

  - by dieguitoweb

  I have to develop a basic social network for an academic purpose; but I need some tips for the users management.. The users are subdivided into 3 groups with different privilege: admins,analysts and standards users. For every user should be stored into the database the following information: name,lastname,e-mail,age,password. I'm not quite sure how I should design the database between theese two solutions: 1)one table called 'users' with the 'role' attribute that explain what a user can do and what can't do, and the permissions are managed via php 2)every application user is a database user created with the query 'CREATE ROLE' (It's a postgres database) and he has permissions on some tables granted with the 'GRANT' statement You should take into account that the project is for a database exam.. thanks

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• Fetch last item in a category that fits specific criteria

  - by Franz

  Let's assume I have a database with two tables: categories and articles. Every article belongs to a category. Now, let's assume I want to fetch the latest article of each category that fits a specific criteria (read: the article does). If it weren't for that extra criteria, I could just add a column called last_article_id or something similar to the categories table - even though that wouldn't be properly normalized. How can I do this though? I assume there's something using GROUP BY and HAVING?

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• stars and slideshow input not working in IE browsers

  - by pradeep

  http://ratingscorner.com/product_rating.php?alias=Rashtreeya-Vidyalaya-College-of-Engineering-Mysore-Road-Bangalore&product=colleges I have a page like this .this works very well in all browsers, but not in IE. problem in IE is that : 1. If you go to "your ratings" tab in second section. the stars and input are not clickable only. 2. and the gap between tabs and tables are more in IE .. tried to check in firebug also. the element has not margin or padding at bottom. the slideshow also does not work in IE

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• Can a primary key be equal to a different column?

  - by eric

  I know that a primary key must be unique, but is it okay for a primary key to be equal to a different column in the same table by coincidence? For instance, I have 2 tables. One table is called person that holds information about a person (ID, email, telephone, address, name). The other table is staff (ID, pID(person ID), salary, position). In staff the ID column is the primary key and is used to uniquely identify a staff member. The number is from 1 - 100. However, the pID (person ID) may be equal to the ID. For instance the staff ID may be 1 and the pID that it references to may be equal to 1. Is that okay?

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• Creating custom ribbon with SQL Server linked Access application

  - by andy

  I'm just learning about creating custom ribbons in Access 2010, but I'm running into an issue. The Access application I'm working with is connected to a SQL Server backend (connected, not just linked tables). As I understand it, the USysRibbons table needs to exist in the Access application itself, and not in a connected SQL Server. How does one go about creating a table in an Access application that is already linked to a SQL Server? I tried creating the table in a blank database and then importing it into the Access application without any luck.

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• Storing Data as XML BLOB

  - by NBrowne

  Hi, At the moment the team i am working with is looking into the possibility of storing data which is entered by users from a series of input wizard screens as an XML blob in the database. the main reason for this being that i would like to write the input wizard as a component which can be brought into a number of systems without having to bring with it a large table structure. To try to clarify if the wizard has 100 input fields (for example) then if i go with the normal relational db structure then their will be a 1 to 1 relationship so will have 100 columns in database. So to get this working in another system will have to bring the tables,strore procedures etc into the new system. I have a number of reservations about this but i would like peoples opinions?? thanks

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• Codeigniter setting multiple where conditions, how to unset one

  - by Dustin

  I've got a script that is a notify_url from paypal that is supposed to update multiple tables in my database using the following code: //update first table $this-db-where('someid', $somid); $this-db-update('table', $data); ///update second table $this-db-where('somesecondid', $somesecondid) $this-db-update('anothertable', $data2); Then I get the following error: Unknown column 'somesecondid' in 'where clause' UPDATE anothertable SET avail = 0 WHERE someid = '13' AND somesecondid = '199' So codeigniter is combining those where clauses into a single query. Is there a way to unset the first one so it only has "UPDATE anothertable SET avail=0 WHERE somesecondid = 199" ? Thanks!

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• Complicated Order By Clause?

  - by Todd

  Hi. I need to do what to me is an advanced sort. I have this two tables: Table: Fruit fruitid | received | basketid 1 20100310 2 2 20091205 3 3 20100220 1 4 20091129 2 Table: Basket id | name 1 Big Discounts 2 Premium Fruit 3 Standard Produce I'm not even sure I can plainly state how I want to sort (which is probably a big part of the reason I can't seem to write code to do it, lol). I do a join query and need to sort so everything is organized by basketid. The basketid that has the oldest fruit.received date comes first, then the other rows with the same basketid by date asc, then the basketid with the next earliest fruit.received date followed by the other rows with the same basketid, and so on. So the output would look like this: Fruitid | Received | Basket 4 20091129 Premuim Fruit 1 20100310 Premuim Fruit 2 20091205 Standard Produce 3 20100220 Big Discounts Any ideas how to accomplish this in a single execution?

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• How to use SQLiteOpenHelper without or less restrictive use of Context?

  - by Pentium10

  If you extend SQLiteOpenHelper, for the Constructor you have to use a Context. I am wondering if there is a way to leave this out, and be able to work with database tables without a Context. Or at least be least restrictive, I mean a way of project/class structure that will make history the several context passings I have to do now. As it is my application has several level of classes, chained in each other, and there are a few that connects to the database, but have no whatsoever influence on the interface, so they don't actually need the Context. Are you creating your classes in the way that you pass each time a Context to them? If not, how you do, how you reuse a Context in a short class?

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• MVC way of handling data input

  - by korki

  I have a data input module where I add the information of my product and its sub information like: product basic info product price info product price details price info and price details are related to product and are lists In my web forms approach I would store my main product object on the view state and I would populate it's pricing info and details while doing ajax postbacks. This way I can create a compact module that is very user friendly in terms of defining a lot of data from one place without the need to enter these data from seperate modules. And when I am done I would do one product.save() and that would persist all the data to the respective tables on db. Now I am building similar app on .net mvc framework and pondering on what would be the good way of handling this on mvc. I don't resonate towards storing all this on client side till I click save. And saving to the db after each action makes me remember the days I was coding on asp. Will appreciate your inputs on ways to approach this on mvc framework

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• Select records by comparing subsets

  - by devnull

  Given two tables (the rows in each table are distinct): 1) x | y z 2) x | y z ------- --- ------- --- 1 | a a 1 | a a 1 | b b 1 | b b 2 | a 1 | c 2 | b 2 | a 2 | c 2 | b 2 | c Is there a way to select the values in the x column of the first table for which all the values in the y column (for that x) are found in the z column of the second table? In case 1), expected result is 1. If c is added to the second table then the expected result is 2. In case 2), expected result is no record since neither of the subsets in the first table matches the subset in the second table. If c is added to the second table then the expected result is 1, 2. I've tried using except and intersect to compare subsets of first table with the second table, which works fine, but it takes too long on the intersect part and I can't figure out why (the first table has about 10.000 records and the second has around 10). EDIT: I've updated the question to provide an extra scenario.

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• Clientside Javascript --> Serverside Java --> user is served a .doc

  - by ignorantslut

  I am helping someone out with a javascript-based web app (even though I know next to nothing about web development) and we are unsure about the best way to implement a feature we'd like to have. Basically, the user will be using our tool to view all kinds of boring data in tables, columns, etc. via javascript. We want to implement a feature where the user can click a button or link that then allows the user to download the displayed data in a .doc file. Our basic idea so far is something like: call a Java function on the server with the desired data passed in as a String when the link is clicked generate the .doc file on the server automatically "open" a link to the file in the client's browser to initiate the download Is this possible? If so, is it feasible? Or, can you recommend a better solution? edit: the data does not reside on the server; rather, it is queried from a SQL database

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• Using Forms authentication with remote auth system?

  - by chobo

  I am working on a website that uses a remote websites database to check for authentication (they are both share some database tables, but are separate website...) Right now I check the username and password against the remote websites account / member table, if there is a match I create a session. Questions: Is this secure? On authenticated pages I just check if a session of a specific type exists.Is it possible for someone to create an empty session or something that could bypass this? Is it possible to use Forms authentication with this setup? Right now if a user is authenticated I just get an object back with the username, email and id.

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