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  • Why do I have to set the max length of every damn text column in the database?

    - by John Leidegren
    Why is it that every RDBMS insists that you tell it what the max length of a text field is going to be... why can't it just infer this information form the data that's put into the database? I've mostly worked with MS SQL Server, but every other database I know also demands that you set these arbitrary limits on your data schema. The reality is that this is not particulay helpful or friendly to work with becuase the business requirements change all the time and almost every day some end-user is trying to put a lot of text into that column. Does any one with some inner working knowledge of a RDBMS know why we just don't infer the limits from the data that's put into the storage? I'm not talking about guessing the type information, but guessing the limits of a particular text column. I mean, there's a reason why I don't use nvarchar(max) on every text column in the database.

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  • Mobile news reader

    - by Sergej Andrejev
    I'm using C# and probably .Net compact framework. How should I design mobile news reader (RSS, Atom...). What are risks I should be aware before I start? What libraries are there to help me read and parse data and synchronize it when going from offline mode?

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  • Help on choosing which SQL Server 2008 scale-out solution to pick (replication, ...)

    - by usr
    I am currently crossing the jungle of SQL Server scale-out technologies like replication, log-shipping, mirroring... I have the following constraints on my choice: I want the read-only load to be spread accross the primary and the secondary (mirror, subscriber) server Write load can be sent directly to the primary server The solution should be nearly maintainance free. Schema changes should just replicate to the secondary server (attention: replication has some serious constraints here as it seems) Written data should be accessible very quickly (in under 1s, but better would be instantaneously) on the secondary server On server failure I can tollerate up to one hour of data loss easily. I am more concerned with easy scalability Here are some options for what I could pick: http://msdn.microsoft.com/en-us/library/bb510414.aspx. Any experience you could share?

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  • Rails - how to serialize a tree not in a form

    - by tiny_clanger
    I started with the standard scriptaculous drag and drop tree, and that all works fine. Then started implementing this: http://www.artweb-design.de/2008/5/30/scriptaculous-sortabletree which gives a good drag and drop tree Where I am stuck is how to get serialize the tree (unordered list)? It's not in a form, and I can't find a way to serialize it to move onto setting up the AJAX update.

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  • Visual Studio C++ adds "junk" to my programs

    - by sub
    I have looked into the binaries produced by MSVC 2010 from my source code, and saw everything being filled with "junk". I don't know how to explain, but my executables are being added too much unnecessary information, like: Lots of Microsoft default error messages, I don't want them XML schema settings (Why!?) Other things not important for the execution of the main program How can I stop MSVC doing this? Do I have to switch to GCC? In all other programs (written in C++ too, from Word processors to games), this junk simply doesn't exist.

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  • Generate service layer with Hibernate

    - by gmate
    Hi all! I generate *.hbm.xml mapping files and *.java file from the DB schema, with Hibernate tools. My question is, that is there any option, to generate service classes also? These are the classes where I implement the store(), find(), delete(), etc... methods. I know that for C# there are many solutions to generate almost everything. I'm looking for the same, but with Hibernate. Is there any? Thanks for every reply in advance!

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  • exactly what does rake db:migrate do?

    - by happythenewsad
    Does rake db:migrate only add new migrations, or does it drop all migrations/changes and build everything new? I think rake is throwing an error because it is trying to access a table attribute in migration 040 that was deleted in migration 042. somehow my DB and rake are out of synch and I want to fix them. for you experts out there - is it common for rake to get out of synch with migrations? how can I avoid this (no, I do not hand-edit my schema or rake files).

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  • Optimal search queries

    - by Macros
    Following on from my last question http://stackoverflow.com/questions/2788082/sql-server-query-performance, and discovering that my method of allowing optional parameters in a search query is sub optimal, does anyone have guidelines on how to approach this? For example, say I have an application table, a customer table and a contact details table, and I want to create an SP which allows searching on some, none or all of surname, homephone, mobile and app ID, I may use something like the following: select * from application a inner join customer c on a.customerid = a.id left join contact hp on (c.id = hp.customerid and hp.contacttype = 'homephone') left join contact mob on (c.id = mob.customerid and mob.contacttype = 'mobile') where (a.ID = @ID or @ID is null) and (c.Surname = @Surname or @Surname is null) and (HP.phonenumber = @Homphone or @Homephone is null) and (MOB.phonenumber = @Mobile or @Mobile is null) The schema used above isn't real, and I wouldn't be using select * in a real world scenario, it is the construction of the where clause I am interested in. Is there a better approach, either dynamic sql or an alternative which can achieve the same result, without the need for many nested conditionals. Some SPs may have 10 - 15 criteria used in this way

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  • Need help in understanding a SELECT query

    - by Grant Smith
    I have a following query. It uses only one table (Customers) from Northwind database. I completely have no idea how does it work, and what its intention is. I hope there is a lot of DBAs here so I ask for explanation. particularly don't know what the OVER and PARTITION does here. WITH NumberedWomen AS ( SELECT CustomerId ,ROW_NUMBER() OVER ( PARTITION BY c.Country ORDER BY LEN(c.CompanyName) ASC ) women FROM Customers c ) SELECT * FROM NumberedWomen WHERE women > 3 If you needed the db schema, it is here

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  • MySQL Insert Query Randomly Takes a Long Time

    - by ShimmerTroll
    I am using MySQL to manage session data for my PHP application. When testing the app, it is usually very quick and responsive. However, seemingly randomly the response will stall before finally completing after a few seconds. I have narrowed the problem down to the session write query which looks something like this: INSERT INTO Session VALUES('lvg0p9peb1vd55tue9nvh460a7', '1275704013', '') ON DUPLICATE KEY UPDATE sessAccess='1275704013',sessData=''; The slow query log has this information: Query_time: 0.524446 Lock_time: 0.000046 Rows_sent: 0 Rows_examined: 0 This happens about 1 out of every 10 times. The query usually only takes ~0.0044 sec. The table is InnoDB with about 60 rows. sessId is the primary key with a BTREE index. Since this is accessed on every page view, it is clearly not an acceptable execution time. Why is this happening? Update: Table schema is: sessId:varchar(32), sessAccess:int(10), sessData:text

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  • PHP front-end and Java back-end for a web app?

    - by Raydon
    I'm designing a web application. I was wondering if it was feasible to design a php front end (using some php framework e.g. CakePHP), which stores and retrieves data to display to the user. Then develop a java backend which listens to the database for changes, and depending on what was changed, performs some actions and updates the database. Any thoughts on this type of implementation would be appreciated.

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  • how did i break :method -> :delete

    - by Tallboy
    i refactored my entire application and gave it a whole new design. The one thing that seems to be broken is all the original link_to methods I had which were :method = :delete are now getting sent as a GET request. The only thing I did that I can remember that might cause it is delete jquery-rails from the gemfile (I'm just getting it from google ajax). Does anyone have any other ideas what I could have deleted?

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  • rewards the products qualify for

    - by Rod
    products purchased -------------------------- bana bana bana stra kiwi reward requirements table (related to a rewards table) reward id, products ---------------------- 1,bana 1,bana 1,bana 2,stra 2,bana 3,stra 4,cart 5,bana 5,bana 5,oliv Can you help me with sql to get rewards the products purchased qualifies for? In the case above the reward ids would be: 1 2 3 If there is a better design that would make the solution easier I welcome those as well. I'm using product names for the sake of easier explaining, I hope. (I'll replace with product ids later)

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  • What is the best way to partition large tables in SQL Server?

    - by RyanFetz
    In a recent project the "lead" developer designed a database schema where "larger" tables would be split across two seperate databases with a view on the main database which unioned the two seperate database-tables together. The main database is what the application was driven off of so these tables looked and felt like ordinary tables (except some quirkly things around updating). This seemed like a HUGE performance problem. We do see problems with performance around these tables but nothing to make him change his mind about his design. Just wondering what is the best way to do this, or if it is even worth doing?

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  • Pass variables between separate instances of ruby (without writing to a text file or database)

    - by boulder_ruby
    Lets say I'm running a long worker-script in one of several open interactive rails consoles. The script is updating columns in a very, very, very large table of records. I've muted the ActiveRecord logger to speed up the process, and instruct the script to output some record of progress so I know how roughly how long the process is going to take. That is what I am currently doing and it would look something like this: ModelName.all.each_with_index do |r, i| puts i if i % 250 ...runs some process... r.save end Sometimes its two nested arrays running, such that there would be multiple iterators and other things running all at once. Is there a way that I could do something like this and access that variable from a separate rails console? (such that the variable would be overwritten every time the process is run without much slowdown) records = ModelName.all $total = records.count records.each_with_index do |r, i| $i = i ...runs some process... r.save end meanwhile mid-process in other console puts "#{($i/$total * 100).round(2)}% complete" #=> 67.43% complete I know passing global variables from one separate instance of ruby to the next doesn't work. I also just tried this to no effect as well unix console 1 $X=5 echo {$X} #=> 5 unix console 2 echo {$X} #=> "" Lastly, I also know using global variables like this is a major software design pattern no-no. I think that's reasonable, but I'd still like to know how to break that rule if I'd like. Writing to a text file obviously would work. So would writing to a separate database table or something. That's not a bad idea. But the really cool trick would be sharing a variable between two instances without writing to a text file or database column. What would this be called anyway? Tunneling? I don't quite know how to tag this question. Maybe bad-idea is one of them. But honestly design-patterns isn't what this question is about.

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