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• SQLce DAL Linq to Sql or EntityFramework

  - by bretddog

  Hi, I'm learning databases, using SqlCe, and need business object to database mapping. Currently I try to decide if to use Linq to Sql, or EntityFramework. (I understand a bit L2S, but haven't familiarized with EF yet) The program will only be debeloped and used by myself, so I have good control of the priorities: I don't need to consider potential change of database type or data storage type, as I'm quite certain SQLce will stay sufficient. I DO expect continued development and changes to the data scheme while the program is in active use; change business object properties (Hence database columns), and possibly overall table scheme. So old data must be transported to new scheme. I also want to keep a decent degree of layer separation DAL/BLL, although this may not be necessary, it is good for me to learn these principles. My question is: With these priorities, would I have any benefit by choosing either Linq2Sql vs. EntityFramwork? (and please explain why) Btw, the project involves very simple table scheme with only 4-5 tables and very simple relations. Thanks!

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• Database frontend for multiple db engines

  - by xeroxed_yeti

  Hey Stackoverflow, yeah it's spring and a lot of things happens to me... Also changing some software things at my computer, because suddenly everything seems to be boring after starting my laptop. I even changed my wallpaper!!! Besides I'm looking for a new database frontend and after using google with serveral queries I didn't find the right software. You have to know, my laptop and me are very very special :) I'm looking for a database frontend which should have following features can access PostgreSQL and MySQL databases can handle schemata overs a nice sql query tool supports an import and export functionality (something like tab separated text files) it for free looks awesome - every time when a college come to my office he must get the feeling: oh boy, this man really knows his job and should get more money! At the moment I used phpmyadmin, phppgadmin, pgadminIII, mysqladmin and dbVisualizer. Furthermore I was a big fan of the aqua datastudio until it became commercial. This tools offers a great variety of functionalities which can simplify programmes live. However, now you have to buy a license...I'm a scientist and money for software is limited =) So it's my first time (question) here at stackoverflow please be cheerful :)

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• What arguments to use to explain why a SQL DB is far better then a flat file

  - by jamone

  The higher ups in my company were told by good friends that flat files are the way to go, and we should switch from MS SQL server to them for everything we do. We have over 300 servers and hundreds of different databases. From just the few I'm involved with we have 10 billion records in quite a few of them with upwards of 100k new records a day and who knows how many updates... Me and a couple others need to come up with a response saying why we shouldn't do this. Most of our stuff is ASP.NET with some legacy ASP. We thought that making a simple console app that tests/times the same interactions between a flat file (stored on the network) and SQL over the network doing large inserts, searches, updates etc along with things like network disconnects randomly. This would show them how bad flat files can be espically when you are dealing with millions of records. What things should I use in my response? What should I do with my demo code to illustrate this? My sort list so far: Security Concurent access Performance with large ammounts of data Ammount of time to do such a massive rewrite/switch Lack of transactions PITA to map relational data to flat files I fear that this will be a great post on the Daily WTF someday if I can't stop it now.

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• Time delay an external RSS feed

  - by x3ja

  I subscribe to a number of RSS feeds, mostly from within my own timezone (UK: currently GMT+1, a.k.a BST). However I'm also interested in news from New Zealand (currently GMT+12). My problem is caused by my addiction to needing to keep my unread count at, or near, zero. When I load up my RSS reader in the mornings it has gathered all the NZ news at once (normally around 100 items) and I feel compelled either to read them all or to mark them all as read to feed my need for zero-unread-count. I figured a good solution to this would be to time delay the RSS feed somehow, so I would be drip-fed the stories at their time +12 hours, so I could read them through the day as they come in. So my question (or, rather, questions): Does such a thing exist currently & what is it? (no point reworking the wheel) If not: What would be the best way to approach doing this myself? I have access to a Linux web server on which I can run scripts, create databases, store files etc, so there should be a way... I'm most conversant in perl and have done a little fiddling with XML within that, so would naturally process ... or is there some simpler way to do it that I'm missing?

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• How can I synchronise two datatables and update the target in the database?

  - by Craig

  I am trying to synchronise two tables between two databases. I thought that the best way to do this would be to use the DataTable.Merge method. This seems to pick up the changes, but nothing ever gets committed to the database. So far I have: string tableName = "[Table_1]"; string sql = "select * from " + tableName; using (SqlConnection sourceConn = new SqlConnection(ConfigurationManager.ConnectionStrings["source"].ConnectionString)) { SqlDataAdapter sourceAdapter = new SqlDataAdapter(); sourceAdapter.SelectCommand = new SqlCommand(sql, sourceConn); sourceConn.Open(); DataSet sourceDs = new DataSet(); sourceAdapter.Fill(sourceDs); using (SqlConnection targetConn = new SqlConnection(ConfigurationManager.ConnectionStrings["target"].ConnectionString)) { SqlDataAdapter targetAdapter = new SqlDataAdapter(); targetAdapter.SelectCommand = new SqlCommand(sql, targetConn); SqlCommandBuilder builder = new SqlCommandBuilder(targetAdapter); targetAdapter.InsertCommand = builder.GetInsertCommand(); targetAdapter.UpdateCommand = builder.GetUpdateCommand(); targetAdapter.DeleteCommand = builder.GetDeleteCommand(); targetConn.Open(); DataSet targetDs = new DataSet(); targetAdapter.Fill(targetDs); targetDs.Tables[0].TableName = tableName; sourceDs.Tables[0].TableName = tableName; targetDs.Tables[0].Merge(sourceDs.Tables[0]); targetAdapter.Update(targetDs.Tables[0]); } } At the present time, there is one row in the source that is not in the target. This row is never transferred. I have also tried it with an empty target, and nothing is transferred.

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• Database nesting layout confusion

  - by arzon

  I'm no expert in databases and a beginner in Rails, so here goes something which kinda confuses me... Assuming I have three classes as a sample (note that no effort has been made to address any possible Rails reserved words issue in the sample). class File < ActiveRecord::Base has_many :records, :dependent => :destroy accepts_nested_attributes_for :records, :allow_destroy => true end class Record < ActiveRecord::Base belongs_to :file has_many :users, :dependent => :destroy accepts_nested_attributes_for :users, :allow_destroy => true end class User < ActiveRecord::Base belongs_to :record end Upon entering records, the database contents will appear as such. My issue is that if there are a lot of Files for the same Record, there will be duplicate record names. This will also be true if there will be multiple Records for the same user in the the Users table. I was wondering if there is a better way than this so as to have one or more files point to a single Record entry and one or more Records will point to a single User. BTW, the File names are unique. Files table: id name 1 name1 2 name2 3 name3 4 name4 Records table: id file_id record_name record_type 1 1 ForDaisy1 ... 2 2 ForDonald1 ... 3 3 ForDonald2 ... 4 4 ForDaisy1 ... Users table: id record_id username 1 1 Daisy 2 2 Donald 3 3 Donald 4 4 Daisy Is there any way to optimize the database to prevent duplication of entries, or this should really the correct and proper behavior. I spread out the database into different tables to be able to easily add new columns in the future.

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• What arguments to use to explain why SQL Server is far better then a flat file

  - by jamone

  The higher ups in my company were told by good friends that flat files are the way to go, and we should switch from SQL Server to them for everything we do. We have over 300 servers and hundreds of different databases. From just the few I'm involved with we have 10 billion records in quite a few of them with upwards of 100k new records a day and who knows how many updates... Me and a couple others need to come up with a response saying why we shouldn't do this. Most of our stuff is ASP.NET with some legacy ASP. We thought that making a simple console app that tests/times the same interactions between a flat file (stored on the network) and SQL over the network doing large inserts, searches, updates etc along with things like network disconnects randomly. This would show them how bad flat files can be especially when you are dealing with millions of records. What things should I use in my response? What should I do with my demo code to illustrate this? My sort list so far: Security Concurrent access Performance with large amounts of data Amount of time to do such a massive rewrite/switch Lack of transactions PITA to map relational data to flat files NTFS doesn't support tons of files in a directory well I fear that this will be a great post on the Daily WTF someday if I can't stop it now.

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• PHP code displayed in browser

  - by Drake

  so, I'm working on a databases project, and i'm trying to code incrementally. the problem is, when i go to test the php in browser, it displays the php code after my use of "-". the html printing is displayed properly, which is AFTER the point where the - is. here is the php: <?php function getGraphicNovel(){ include_once("./connect.php"); $db_connection = new mysqli($SERVER, $USERNAME, $PASSWORD, $DATABASE); if (mysqli_connect_errno()) { echo("Can't connect to MySQL Server. Error code: " . mysqli_connect_error()); return null; } $stmt = $db_connection->stmt_init(); $returnValue = "invalid"; if($stmt.prepare("select series from graphic_novel_main natural join graphic_novel_misc")) { $stmt->execute(); $stmt->bind_result($series); while ($stmt->fetch()) { echo "<tr><td>" . $series . "</td></tr>"; } $stmt->close(); } $db_connection->close(); } getGraphicNovel(); ?> here is a link to the page. hopefully it works for people outside the school's network. http://plato.cs.virginia.edu/~paw5k/cainedb/viewall.html if anyone knows why this is happening, your input would be great!

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• SQLite for personal use

  - by ALife

  What are the applications for your personal use that needs a small database like SQLite? I am thinking of trying a few popular databases and SQLite is surely the first one I am planning to try since I know barely nothing about database except some simple programming years ago. I learned that SQLite is good for personal use. But embarrassingly I do not see any application except maybe managing my list of phone numbers/contact info, which has probably a few hundred items. What's your experience? FYI, I use EndNote for my reference and softcopy of books, and I feel iTunes' music/media management is ok since I am not a frequent user anyway. And others? I do lots of coding, but I just use some simple etags tools for that. And I pretty much use .txt file (sometimes in the asciidoc style) for my notes. I have quite a bunch of notes, but not that many either. So, really, what are your personal applications that need a small database instead of existing tools and plain text files?

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• How to make safe frequent DataSource switches for AbstractRoutingDataSource?

  - by serg555

  I implemented Dynamic DataSource Routing for Spring+Hibernate according to this article. I have several databases with same structure and I need to select which db will run each specific query. Everything works fine on localhost, but I am worrying about how this will hold up in real web site environment. They are using some static context holder to determine which datasource to use: public class CustomerContextHolder { private static final ThreadLocal<CustomerType> contextHolder = new ThreadLocal<CustomerType>(); public static void setCustomerType(CustomerType customerType) { Assert.notNull(customerType, "customerType cannot be null"); contextHolder.set(customerType); } public static CustomerType getCustomerType() { return (CustomerType) contextHolder.get(); } public static void clearCustomerType() { contextHolder.remove(); } } It is wrapped inside some ThreadLocal container, but what exactly does that mean? What will happen when two web requests call this piece of code in parallel: CustomerContextHolder.setCustomerType(CustomerType.GOLD); //<another user will switch customer type here to CustomerType.SILVER in another request> List<Item> goldItems = catalog.getItems(); Is every web request wrapped into its own thread in Spring MVC? Will CustomerContextHolder.setCustomerType() changes be visible to other web users? My controllers have synchronizeOnSession=true. How to make sure that nobody else will switch datasource until I run required query for current user? Thanks.

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• Guid Primary /Foreign Key dilemma SQL Server

  - by Xience

  Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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• MySQL Stored Procedures : Use a variable as the database name in a cursor declaration

  - by Justin

  I need to use a variable to indicate what database to query in the declaration of a cursor. Here is a short snippet of the code : CREATE PROCEDURE `update_cdrs_lnp_data`(IN dbName VARCHAR(25), OUT returnCode SMALLINT) cdr_records:BEGIN DECLARE cdr_record_cursor CURSOR FOR SELECT cdrs_id, called, calling FROM dbName.cdrs WHERE lrn_checked = 'N'; # Setup logging DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN #call log_debug('Got exception in update_cdrs_lnp_data'); SET returnCode = -1; END; As you can see, I'm TRYING to use the variable dbName to indicate in which database the query should occur within. However, MySQL will NOT allow that. I also tried things such as : CREATE PROCEDURE `update_cdrs_lnp_data`(IN dbName VARCHAR(25), OUT returnCode SMALLINT) cdr_records:BEGIN DECLARE cdr_record_cursor CURSOR FOR SET @query = CONCAT("SELECT cdrs_id, called, calling FROM " ,dbName, ".cdrs WHERE lrn_checked = 'N' "); PREPARE STMT FROM @query; EXECUTE STMT; # Setup logging DECLARE EXIT HANDLER FOR SQLEXCEPTION BEGIN #call log_debug('Got exception in update_cdrs_lnp_data'); SET returnCode = -1; END; Of course this doesn't work either as MySQL only allows a standard SQL statement in the cursor declaration. Can anyone think of a way to use the same stored procedure in multiple databases by passing in the name of the db that should be affected?

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• Technology Plan - Which tools should I use?

  - by Armadillo

  Hi, Soon, I'll start my own software company. My primary product/solution will be a Billing/Invoice Software. In a near future, I pretend to expand this first module to an ERP. My app should be able to run as a stand-alone application and as a Web-based application (so there will be, probably two GUI for the same Database). My problem, now, is to choose the right tools; I'm talking about what programming language(s) should I use, what kind of database should I choose, and stuff like that. I'm primarily a VB6 programmer, so probably I'll choose the .net framework (vb/c#). But I'm seriously thinking about Java. Java has 2 "pros" that I really like: write once, run anywhere and it is free (I think...). I've been thinking about RIAs too, but I just don't have any substantial feedback about them... Then, I'll need a report tool. Crystal Reports? HTML based Reports? Other? Databases: I'm not sure if I should use SQL-Server Express or PostgreSQL (or other). I'd be happy to hear any comments and advices Thanks

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• Ruby on Rails Mongrel web server stuck when MySQL service is running

  - by Marcos Buarque

  Hi, I am a Ruby on Rails newbie and already have a problem. I have started the Mongrel web server and it works fine when MySQL service isn't running. But when MySQL is on, Mongrel stucks. It ceases from serving the pages. So far, I have tested the localhost:3000 URL. When MySQL is off, it serves the page. When I click "about application's environment", I get the messasge (of course) "Can't connect to MySQL server on 'localhost' (10061)". After starting the MySQL service and refreshing, I get no more answer and Mongrel does not serve the webpage. It gets stuck with no answer to the browser. Then I have to stop the webserver and restart it. I have installed mysql2 gem with the command gem install mysql2. I was able to create the _test and _development databases with the command line rake db:create. I have tested with MySQL root user and blank password and also tried with a superuser user I have created. No success. Here is the server log: ======================== Started GET "/rails/info/properties" for 127.0.0.1 at Fri Dec 24 17:41:25 -0200 2010 Mysql2::Error (Can't connect to MySQL server on 'localhost' (10061)): Rendered C:/Ruby187/lib/ruby/gems/1.8/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms) Rendered C:/Ruby187/lib/ruby/gems/1.8/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (5.0ms) Rendered C:/Ruby187/lib/ruby/gems/1.8/gems/actionpack-3.0.3/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (35.0ms) ================= I am running on a Windows 7 environment with firewall down.

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• using a database and deploying the application

  - by evan

  I have a WPF application that stores a large amount of information in XML files and as the user uses the application they add more information to the XML files. It's basically using the XML files as a database. Since over the life of the program the XML files have gotten quite large, and I've been think about putting the data on a website, I've been looking into how to move all the information into an SQL database. I've used SQL databases with web applications (PHP, Ruby, and ASP.NET) but never with a Desktop application. Ideally I'd like to be able to keep all the information in one database file and distribute it along with the application without requiring the user to connect to a remote database (so they don't need an internet connection - though eventually it would be nice if could compare the local file's version with one online somewhere and update if necessary) and without making them install a local database server on their computer. Is this possible? I'd also like to use LINQ with any new database solution so switching to a database doesn't force to many changes (I read the XML with LINQ). I'm sure this question has been asked and that there are already some good tutorials on the subject but I just can't find them.

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• Sorting a list in PHP

  - by Andy

  Alright, so I've just (almost) finished my first little php script. Basically all it does is handling forms. It writes whatever the user put in to the fields of the form to a text file, then I include that text file in the index of the little page I have set up. So, currently it writes to the beginning of the text file (but doesn't overwrite previous data). But, several users wants this list to be alphabetically sorted instead. So what I want to do is make whatever they submit fall into the list in alphabetical order. The thing here is also that all I use in the text file are divs. The list is basically 'divided' into 3 parts. 'Title', 'Link', and 'Poster'. All I have done is positioned them with css. So, can I sort this list (the titles, in this case) alphabetically and still have the 'link' and 'poster' information assigned the way they already are, but just with the titles sorted? It don't use databases at all on my site, so there is no database handling at all used in this script (mainly because I'm not experienced at all in this).

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• Rails Binary Stream support

  - by Craig Walker

  I'm going to be starting a project soon that requires support for large-ish binary files. I'd like to use Ruby on Rails for the webapp, but I'm concerned with the BLOB support. In my experience with other languages, frameworks, and databases, BLOBs are often overlooked and thus have poor, difficult, and/or buggy functionality. Does RoR spport BLOBs adequately? Are there any gotchas that creep up once you're already committed to Rails? BTW: I want to be using PostgreSQL and/or MySQL as the backend database. Obviously, BLOB support in the underlying database is important. For the moment, I want to avoid focusing on the DB's BLOB capabilities; I'm more interested in how Rails itself reacts. Ideally, Rails should be hiding the details of the database from me, and so I should be able to switch from one to the other. If this is not the case (ie: there's some problem with using Rails with a particular DB) then please do mention it. UPDATE: Also, I'm not just talking about ActiveRecord here. I'll need to handle binary files on the HTTP side (file upload effectively). That means getting access to the appropriate HTTP headers and streams via Rails. I've updated the question title and description to reflect this.

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• Best approach for Java/Maven/JPA/Hibernate build with multiple database vendor support?

  - by HDave

  I have an enterprise application that uses a single database, but the application needs to support mysql, oracle, and sql*server as installation options. To try to remain portable we are using JPA annotations with Hibernate as the implementation. We also have a test-bed instance of each database running for development. The app is building nicely in Maven, and I've played around with the hibernate3-maven-plugin and can auto-generate DDL for a given database dialect. What is the best way to approach this so that individual developers can easily test against all three databases and our Hudson based CI server can build things propertly. More specifically: 1) I thought the hbm2ddl goal in the hibernate3-maven-plugin would just generate a schema file, but apparently it connects to a live database and attempts to create the schema. Is there a way to have this just create the schema file for each database dialect without connecting to a database? 2) If the hibernate3-maven-plug insists on actually creating the database schema, is there a way to have it drop the database and recreate it before creating the schema? 3) I am thinking that each developer (and the hudson build machine) should have their own separate database on each database server. Is this typical? 4) Will developers have to run Maven three times...once for each database vendor? If so, how do I merge the results on the build machine? 5) There is a hbm2doc goal within hibernate3-maven-plugin. It seems overkill to run this three times...I gotta believe it'd be nearly identical for each database.

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• Implementing a 1 to many relationship with SQLite

  - by Patrick

  I have the following schema implemented successfully in my application. The application connects desk unit channels to IO unit channels. The DeskUnits and IOUnits tables are basically just a list of desk/IO units and the number of channels on each. For example a desk could be 4 or 12 channel. CREATE TABLE DeskUnits (Name TEXT, NumChannels NUMERIC); CREATE TABLE IOUnits (Name TEXT, NumChannels NUMERIC); CREATE TABLE RoutingTable (DeskUnitName TEXT, DeskUnitChannel NUMERIC, IOUnitName TEXT, IOUnitChannel NUMERIC); The RoutingTable 'table' then connects each DeskUnit channel to an IOUnit channel. For example the DeskUnit called "Desk1" channel 1 may route to IOunit name "IOUnit1" channel 2, etc. So far I hope this is pretty straightforward and understandable. The problem is, however, this is a strictly 1 to 1 relationship. Any DeskUnit channel can route to only 1 IOUnit channel. Now, I need to implement a 1 to many relationship. Where any DeskUnit channel can connect to multiple IOUnit channels. I realise I may have to rearrange the tables completely, but I am not sure the best way to go about this. I am fairly new to SQLite and databases in general so any help would be appreciated. Thanks Patrick

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• Syncing magento database froms development to production

  - by ringerce

  I use git for version control. I have a development, staging and production environment. When I finish in development I push to staging for review by the client. When approved, I push changes from staging to production. That works fine as long as there is no database changes. What happens if I install modules via Magento connect on local development and it makes database modifications. How would I push those changes up to the production server since the production server is always changing? Edit: I wrote two shell scripts. One that pulls the production database down to my development server, replaces base url with develpment url and updates my development db accordingly. It also leaves the production sql dump behind to be added to my git repo. I'm not really sure if it's beneficial to keep the raw dumps in source control but I'm going to try it out. The second scripts moves the development database up to staging and essentially performs the same operations as the first. Now when it comes time to move to production I pull the updated production repo into the production server and allow magento to do it's thing. I also started using SQLYog recently and it has a database comparison wizard which will give me the differences in my development and production databases and allow me to merge the changes in selectively. It always creates a migration script that I added to source control as well. If anything goes wrong I can run the comparison to see if anything was missed. Does this sounds like a decent workflow to you guys?

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• How to convert Unicode strings (\u00e2, etc) into NSString for display?

  - by karlbecker_com

  I am trying to support arbitrary unicode from a variety of international users. They have already put a bunch of data into sqlite databases on their iPhones, and now I want to capture the data into a database, then send it back to their device. Right now I am using a php page that is sending data back to from an internet mysql database. The data is saved in the mysql database properly, but when it's sent back it comes out as unicode text, such as Frank\u00e2\u0080\u0099s iPad instead of just Frank's iPad where the apostrophe should really be a curly apostrophe. The answer posted to another question indicates that there is no built-in Cocoa methods to convert the "\u00e2\u0080\u0099" portion of the unicode string from the webserver to an NSString object. Is this correct? That seems really surprising (and scarily disappointing), since Cocoa definitely allows input from many different Unicode characters, and I need to support any arbitrary language that I have never heard of, and all of the possible characters. I save them to and from the local sqlite database just fine now, but once I send it to a web server, then perhaps pull down different data, I want to ensure the data pulled from the web server is correctly formatted.

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• Web Shop Schema - Document Db

  - by Maxem

  I'd like to evaluate a document db, probably mongo db in an ASP.Net MVC web shop. A little reasoning at the beginning: There are about 2 million products. The product model would be pretty bad for rdbms as there'd be many different kinds of products with unique attributes. For example, there'd be books which have isbn, authors, title, pages etc as well as dvds with play time, directors, artists etc and quite a few more types. In the end, I'd have about 9 different products with a combined column count (counting common columns like title only once) of about 70 to 100 whereas each individual product has 15 columns at most. The three commonly used ways in RDBMS would be: EAV model which would have pretty bad performance characteristics and would make it either impractical or perform even worse if I'd like to display the author of a book in a list of different products (think start page, recommended products etc.). Ignore the column count and put it all in the product table: Although I deal with somewhat bigger databases (row wise), I don't have any experience with tables with more than 20 columns as far as performance is concered but I guess 100 columns would have some implications. Create a table for each product type: I personally don't like this approach as it complicates everything else. C# Driver / Classes: I'd like to use the NoRM driver and so far I think i'll try to create a product dto that contains all properties (grouped within detail classes like book details, except for those properties that should be displayed on list views etc.). In the app I'll use BookBehavior / DvdBehaviour which are wrappers around a product dto but only expose the revelent Properties. My questions now: Are my performance concerns with the many columns approach valid? Did I overlook something and there is a much better way to do it in an RDBMS? Is MongoDb on Windows stable enough? Does my approach with different behaviour wrappers make sense?

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• Set "Start With" value for Oracle sequence dynamically

  - by Allan

  I'm trying to create a release script that can be deployed on multiple databases, but where the data can be merged back together at a later date. The obvious way to handle this is to set the sequence numbers for production data sufficiently high in subsequent deployments to prevent collisions. The problem is in coming up with a release script that will accept the environment number and set the "Start With" value of the sequences appropriately. Ideally, I'd like to use something like this: ACCEPT EnvironNum PROMPT 'Enter the Environment Number: ' --[more scripting] CREATE SEQUENCE seq1 START WITH &EnvironNum*100000; --[more scripting] This doesn't work because you can't evaluate a numeric expression in DDL. Another option is to create the sequences using dynamic SQL via PL/SQL. ACCEPT EnvironNum PROMPT 'Enter the Environment Number: ' --[more scripting] EXEC execute immediate 'CREATE SEQUENCE seq1 START WITH ' || &EnvironNum*100000; --[more scripting] However, I'd prefer to avoid this solution as I generally try to avoid issuing DDL in PL/SQL. Finally, the third option I've come up with is simply to accept the Start With value as a substitution variable, instead of the environment number. Does anyone have a better thought on how to go about this?

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• Architecture for database analytics

  - by David Cournapeau

  Hi, We have an architecture where we provide each customer Business Intelligence-like services for their website (internet merchant). Now, I need to analyze those data internally (for algorithmic improvement, performance tracking, etc...) and those are potentially quite heavy: we have up to millions of rows / customer / day, and I may want to know how many queries we had in the last month, weekly compared, etc... that is the order of billions entries if not more. The way it is currently done is quite standard: daily scripts which scan the databases, and generate big CSV files. I don't like this solutions for several reasons: as typical with those kinds of scripts, they fall into the write-once and never-touched-again category tracking things in "real-time" is necessary (we have separate toolset to query the last few hours ATM). this is slow and non-"agile" Although I have some experience in dealing with huge datasets for scientific usage, I am a complete beginner as far as traditional RDBM go. It seems that using column-oriented database for analytics could be a solution (the analytics don't need most of the data we have in the app database), but I would like to know what other options are available for this kind of issues.

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• Multiple inequality conditions (range queries) in NoSQL

  - by pableu

  Hi, I have an application where I'd like to use a NoSQL database, but I still want to do range queries over two different properties, for example select all entries between times T1 and T2 where the noiselevel is smaller than X. On the other hand, I would like to use a NoSQL/Key-Value store because my data is very sparse and diverse, and I do not want to create new tables for every new datatype that I might come across. I know that you cannot use multiple inequality filters for the Google Datastore (source). I also know that this feature is coming (according to this). I know that this is also not possible in CouchDB (source). I think I also more or less understand why this is the case. Now, this makes me wonder.. Is that the case with all NoSQL databases? Can other NoSQL systems make range queries over two different properties? How about, for example, Mongo DB? I've looked in the Documentation, but the only thing I've found was the following snippet in their docu: Note that any of the operators on this page can be combined in the same query document. For example, to find all document where j is not equal to 3 and k is greater than 10, you'd query like so: db.things.find({j: {$ne: 3}, k: {$gt: 10} }); So they use greater-than and not-equal on two different properties. They don't say anything about two inequalities ;-) Any input and enlightenment is welcome :-)

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