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• Pros and cons of sorting data in DB?

  - by Roman

  Let's assume I have a table with field of type VARCHAR. And I need to get data from that table sorted alphabetically by that field. What is the best way (for performance): add sort by field to the SQL-query or sort the data when it's already fetched? I'm using Java (with Hibernate), but I can't tell anything about DB engine. It could be any popular relational database (like MySQL or MS Sql Server or Oracle or HSQL DB or any other). The amount of records in table can vary greatly but let's assume there are 5k records.

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• free public databases with non-trivial table structures?

  - by Caffeine Coma

  I'm looking for some sample database data that I can use for testing and demonstrating a DB tool I am working on. I need a DB that has (preferably) many tables, and many foreign key relationships between the tables. Ideally the data would be in SQL dump format, or at least in something that maintains the foreign key references, and could be easily import into an RDBMS (MySQL or H2). The dataset itself doesn't have to be huge (in fact, best if it's not). I thought about using the Stackoverflow Data Dump, but it's only about 5 tables.

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• High performance querying - Suggestions please

  - by Alex Takitani

  Supposing that I have millions of user profiles, with hundreds of fields (name, gender, preferred pet and so on...). You want to make searches on profiles. Ex.:All profiles that has age between x and y, loves butterflies, hates chocolate.... With database would you choose? Suppose that You have a Facebook like load. Speed is a must. Open Source preferred. I've read a lot about Cassandra, HBase, Mongo, Mysql... I just can't decide.....

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• How to overcome an apparent REST vs. DRY dilemma in rails?

  - by Chris

  A rails app I'm working on features examples of quadratic equations. Obviously, these are all of a common structure: ax^2 + bx + c = 0. I don't want to store every single example of these. I'd rather generate them from a template. Storing hundreds of possible versions of this structure seems highly wasteful and un-DRY. On the other hand, if I generate them, I can't access them again reliably as I could if they were simply multiple database objects. I'm sure there must be a way to overcome this, but I'm still learning rails and I'm obviously not grasping something here. Thanks.

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• Second level cache for java web app and its alternatives

  - by EugeneP

  Between the transitions of the web app I use a Session object to save my objects in. I've heard there's a program called memcached but there's no compiled version of it on the site, besides some people think there are real disadvantages of it. Now I wanna ask you. What are alternatives, pros and cons of different approaches? Is memcached painpul for sysadmins to install? Is it difficult to embed it to the existing infrastructure from the perspective of a sysadmin? What about using a database to hold temporary data between web app transitions? Is it a normal practice?

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• Classic ASP Site Throwing Date Conversion Error After Moving Servers?

  - by leen3o

  I am moving an old store from a Win2003 IIS6 server to a Win2008 IIS7 server, moved everything across including database. The front end seems to work just fine, but when I login it has to do pull in data based on date ranges and now from no where I am getting this error? The conversion of a varchar data type to a datetime data type resulted in an out-of-range value Any ideas why this would do this on the new server and NOT on the old one? No code has changed and the DB is a backup of the one from the old server??

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• checking if records exists in DB, in single step or 2 steps?

  - by Sinan

  Suppose you want to get a record from database which returns a large data and requires multiple joins. So my question would be is it better to use a single query to check if data exists and get the result if it exists. Or do a more simple query to check if data exists then id record exists, query once again to get the result knowing that it exists. Example: 3 tables a, b and ab(junction table) select * from from a, b, ab where condition and condition and condition and condition etc... or select id from a, b ab where condition then if exists do the query above. So I don't know if there is any reason to do the second. Any ideas how this affects DB performance or does it matter at all?

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• algorithm advice for finding maximum items within a time period

  - by darren

  Hi everyone. I have a database schema that is similar to the following: | User | Event | Date |--------|---------------|------ | 111 | Walked dog | 2009-10-1 | 222 | Walked dog | 2009-10-2 | 333 | Fed Fish | 2009-10-5 | 222 | Did Laundry | 2009-10-6 | 111 | Fed Fish | 2009-10-7 | 111 | Walked dog | 2009-10-18 | 222 | Walked dog | 2009-10-19 | 111 | Fed Fish | 2009-10-21 I would like to produce a query that returns the maximum number of times a user performs some action within a time period. For example, given a time period of 5 days, what is the maximum number of times user 111 walked the dog? The most obvious solution would be to start at some zero point and move forward each day, summing up 5 day periods along the way, then taking the maximum total out of all the 5 day windows. the approach seems incredibly costly however. I would appreciate any suggestions you may have.

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• Data not displayed first time in android after copying the file from assets to data folder

  - by Thinkcomplete

  Description I have used the code tip from http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/ to copy a pre-filled data file to the target and handled this in a asynch task Problem : On starting the application it gives error and shuts down first time, starting again without any change it works perfectly fine. So first time after the file is copied, the error comes but after that no issues. Please help Code attached:.. private class CopyDatabase extends AsyncTask<String, Void, Boolean> { private final ProgressDialog dialog = new ProgressDialog(BabyNames.this); protected void onPreExecute() { this.dialog.setMessage("Loading..."); this.dialog.show(); } @Override protected Boolean doInBackground(String... params) { // TODO Auto-generated method stub try { namesDBSQLHelper.createDatabase(); return null; } catch(IOException ioe){ ioe.printStackTrace(); } return null; } protected void onPostExecute(final Boolean success){ if (this.dialog.isShowing()){ this.dialog.dismiss(); } } }

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• PHP or C# script to parse CSV table values to fill in one-to-many table

  - by Yaaqov

  I'm looking for an example of how to split-out comma-delimited data in a field of one table, and fill in a second table with those individual elements, in order to make a one-to-many relational database schema. This is probably really simple, but let me give an example: I'll start with everything in one table, Widgets, which has a "state" field to contain states that have that widget: Table: WIDGET =============================== | id | unit | states | =============================== |1 | abc | AL,AK,CA | ------------------------------- |2 | lmn | VA,NC,SC,GA,FL | ------------------------------- |3 | xyz | KY | =============================== Now, what I'd like to create via code is a second table to be joined to WIDGET called *Widget_ST* that has widget id, widget state id, and widget state name fields, for example Table: WIDGET_ST ============================== | w_id | w_st_id | w_st_name | ------------------------------ |1 | 1 | AL | |1 | 2 | AK | |1 | 3 | CA | |2 | 1 | VA | |2 | 2 | NC | |2 | 1 | SC | |2 | 2 | GA | |2 | 1 | FL | |3 | 1 | KY | ============================== I am learning C# and PHP, so responses in either language would be great. Thanks.

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• "Data type mismatch in criteria expression"

  - by simon

  Hey guys ! I have a problem when i want to insert values from textboxes to my access database ! When i want to save i get that error ("Data type mismatch in criteria expression") The code: string conString = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=C:\Users\Simon\Desktop\test5\test5\test5\save.mdb"; OleDbConnection empConnection = new OleDbConnection(conString); string insertStatement = "INSERT INTO aktivnosti_save " + "([ID_uporabnika],[ID_aktivnosti],[kalorij]) " + "VALUES (@ID_uporabnika,@ID_aktivnosti,@kalorij)"; OleDbCommand insertCommand = new OleDbCommand(insertStatement, empConnection); insertCommand.Parameters.Add("@ID_uporabnika", OleDbType.Char).Value = textBox3.Text; insertCommand.Parameters.Add("@ID_zivila", OleDbType.Char).Value = iDTextBox.Text; insertCommand.Parameters.Add("@kalorij", OleDbType.Char).Value = textBox2.Text; empConnection.Open(); try { int count = insertCommand.ExecuteNonQuery(); } catch (OleDbException ex) { MessageBox.Show(ex.Message); } finally { empConnection.Close(); textBox1.Clear(); textBox2.Clear(); } }

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• Testing a (big) collection retrieved from a db

  - by Bas

  I'm currently doing integration testing on a live database and I have the following sql statement: var date = DateTime.Parse("01-01-2010 20:30:00"); var result = datacontext.Repository<IObject>().Where(r => r.DateTime > date).First(); Assert.IsFalse(result.Finished); I need to test if the results retrieved from the statement, where the given date is less then the date of the object, have Finished set to False. I do not know how many results I get back and currently I'm getting the first object of the list and check if that object has Finished set to false. I know testing only the first item of the list is not valid testing, as a solution for that I could iterate through the list and check all items on Finished, but putting logic in a Test is kinda going against the concept of writing 'good' tests. So my question is: Does anyone have a good solution of how to properly test the results of this list?

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• Methods to achieve first, previous, next and last navigation

  - by Koroviev

  I'm new to programming and have a question about navigation. What are the various methods that can achieve a "First", "Previous", "Next" and "Last" navigation, as seen in article or comic based sites? (Admittedly the "First" link isn't confusing as it can stay static, but what about the others?) For example, on the 50th page, the links would appropriately lead to the 49th and 51st (if it exists, if not it would not function but would automatically become active when such a page exists. In most examples of this I see urls ending with something like ".php?id=50" but am not certain how it's achieved, with a database? Any help will be very much appreciated, thanks.

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• Correct way to safely store token/secret/etc from OAuth?

  - by viatropos

  I just started looking into OAuth and it looks really nice. I have oauth with twitter working in ruby right now. Now I'm wondering, what is the recommended safe way to store the responses in my local database and session? What should I store? Where should I store it? This example twitter-oauth-with-rails app stores a user.id in the session, and the user table has the token and secret. But that seems like it'd be really easy to hack and get the secret by just passing in a slew of test user ids, no?

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• Problem sending php variables to flash game, on facebook

  - by FlashWars

  When I run the app for the first time in a session it works great i get all data form Database(if i logout, and enter with a diffrent account)the swf does not receive the variables. If i run manually the script typing the url address in the browser (typing: http://myserver.com/app/variables.php), and refresh the facebook app, it receives the data perfectly.How can i fix this?I used the URLVariables, URLRequest and flashvars but still with no succes.I asked for help on many forums but without succes, apparently there are many in my situation.Could this porblem be due the fact tha facebook does not allow flash to talk outside? Any help would be highly apreciated!Thanks!!

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• Timeout LinqToSql inserting millions of records

  - by Bas

  I'm inserting approximently 3 million records in a database using this solution. Eventually when the application has been inserting records for a while (my last run lasted around 4 hours), it gives a timeout with the following SqlException: "SqlExcepetion: Timeout expired. The timeoutperiod elapsed prior to completion of the operation or the server is not responding." What's the best way to handle this exception? Is there a way to prevent this from happening or should I catch the exception? Thanks in advance!

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• Statically Compiled Oracle Client Drivers/Code

  - by blockcipher

  Hello, I'm looking to write a command-line program that can execute database scripts against an Oracle server, however the machine the program will be run on may not have an Oracle client installed on it. I also don't want to rely on a language that requires a VM as there's no guarantee that the VM will be installed, so a language like C is preferable for this. Is there a way that I can statically compile/build this program and not have to have the user install the Oracle client on that machine? I'm trying to be as unobtrusive as possible. Thanks.

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• Search SQL Question Between Related Two Tables

  - by mTuran

  Hi, I am writing some kind of search engine for my web application and i have a problem. I have 2 tables first of is projects table: PROJECTS TABLE id int(11) NO PRI NULL auto_increment employer_id int(11) NO MUL NULL project_title varchar(100) NO MUL NULL project_description text NO NULL project_budget int(11) NO NULL project_allowedtime int(11) NO NULL project_deadline datetime NO NULL total_bids int(11) NO NULL average_bid int(11) NO NULL created datetime NO MUL NULL active tinyint(1) NO MUL NULL PROJECTS_SKILLS TABLE project_id int(11) NO MUL NULL skill_id int(11) NO MUL NULL For example: I want ask this query to database: 1-) Skills are 5 and 7. 2-) Order results by created 3-) project title contains "php" word. 4-) Returned rows should contain projects.* columuns. 5-) Projects should be distinct(i don't want same projects in return of query). Please write sql query that ensure these conditions. Thank You.

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• How do I find the top N batters per year?

  - by Drew Stephens

  I'm playing around with the Lahman Baseball Database in a MySQL instance. I want to find the players who topped home runs (HR) for each year. The Batting table has the following (relevant parts) of its schema: +-----------+----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+----------------------+------+-----+---------+-------+ | playerID | varchar(9) | NO | PRI | | | | yearID | smallint(4) unsigned | NO | PRI | 0 | | | HR | smallint(3) unsigned | YES | | NULL | | +-----------+----------------------+------+-----+---------+-------+ For each year, every player has an entry (between hundreds and 12k per year, going back to 1871). Getting the top N hitters for a single year is easy: SELECT playerID,yearID,HR FROM Batting WHERE yearID=2009 ORDER BY HR DESC LIMIT 3; +-----------+--------+------+ | playerID | yearID | HR | +-----------+--------+------+ | pujolal01 | 2009 | 47 | | fieldpr01 | 2009 | 46 | | howarry01 | 2009 | 45 | +-----------+--------+------+ But I'm interested in finding the top 3 from every year. I've found solutions like this, describing how to select the top from a category and I've tried to apply it to my problem, only to end up with a query that never returns: SELECT b.yearID, b.playerID, b.HR FROM Batting AS b LEFT JOIN Batting b2 ON (b.yearID=b2.yearID AND b.HR <= b2.HR) GROUP BY b.yearID HAVING COUNT(*) <= 3; Where have I gone wrong?

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• PHP and MS Access: Number of Records returned by SELECT query

  - by VarunGupta

  I am running following PHP code to interact with a MS Access database. $odbc_con = new COM("ADODB.Connection"); $constr = "DRIVER={Microsoft Access Driver (*.mdb)}; DBQ=" . $db_path . ";"; $odbc_con -> open($constr); $rs_select = $odbc_con -> execute ("SELECT * FROM Main"); Using ($rs_select - RecordCount) gives -1 though the query is returning non-zero records. (a) What can be the reason? (b) Is there any way out? I have also tried using count($rs_select -> GetRows()). This satisfies the need but looks inefficient as it will involve copying of all the records into an array first.

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• Drupal: I cannot connect to the database.. please help

  - by Patrick

  hi, I've hard time to make Drupal work on IIS Microsoft server. I've succesfully run Joomla on the same server so I'm pretty sure the following information are correct: host: localhost user: user pass: pass databaseName = servername_databasename I've set the following line in settings.php file: $db_url = 'mysql://user:password@localhost/servername_databasename'; but what I get is this: If you are the maintainer of this site, please check your database settings in the settings.php file and ensure that your hosting provider's database server is running. For more help, see the handbook, or contact your hosting provider. I don't get any other error message such as: database doesn't exist, user/pass wrong.. just this. The database is running, I can access with phpmyadmin. I've tried both "mysql" and "mysqli". The host is a private server (IIS Microsoft), the database is Mysql The database and website files upload have also been succesfull.. so I dunno what to do to fix this issue. thanks

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• Joining links together in a dictionary

  - by ptabatt

  Hi guys, I'm student here, new to python and programming in general. I have a dictionary links which holds a tuple mapped to a number. How can I join the second url in the second tuple together with the urljoin() function? What I'm trying to do is get complete links so I can run a recursive function search() which takes a complete url as an arguement, finds all the links in each url and stores the number of links mapped to the links in a database. So far, I have: links {('href', 'http://reed.cs.depaul.edu/lperkovic/csc242/test2.html'): 1, ('href', 'test3.html'): 1} I want http://reed.cs.depaul.edu/lperkovic/csc242/test3.html...

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• What ORMs work well with Scala?

  - by Clinton R. Nixon

  I'm about to write a Scala command-line application that relies on a MySQL database. I've been looking around for ORMs, and am having trouble finding one that will work well. The Lift ORM looks nice, but I'm not sure it can be decoupled from the entire Lift web framework. ActiveObjects also looks OK, but the author says that it may not work well with Scala. I'm not coming to Scala from Java, so I don't know all the options. Has anyone used an ORM with Scala, and if so, what did you use and how well did it work?

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• Should I use integer primary IDs?

  - by arthurprs

  For example, I always generate an auto-increment field for the users table, but I also specify a UNIQUE index on their usernames. There are situations that I first need to get the userId for a given username and then execute the desired query, or use a JOIN in the desired query. It's 2 trips to the database or a JOIN vs. a varchar index. Should I use integer primary IDs? Is there a real performance benefit on INT over small VARCHAR indexes?

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• Rails 3: Validate combined values

  - by Cimm

  In Rails 2.x you can use validations to make sure you have a unique combined value like this: validates_uniqueness_of :husband, :scope => :wife In the corresponding migration it could look like this: add_index :family, [:husband, :wife], :unique => true This would make sure the husband/wife combination is unique in the database. Now, in Rails 3 the validation syntax changed and the scope attribute seems to be gone. It now looks like: validates :husband, :presence => true Any idea how I can achieve the combined validation in Rails 3? The Rails 2.x validations still work in Rails 3 so I can still use the first example but it looks so "old", are there better ways?

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