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• Copying Some from a PostgreSQL Server to Another

  - by whollychao

  I am in need of an application that can periodically transmit select rows from a PostgreSQL database across a network to a second PostgreSQL server. Typically these will be the most recent row added, pulled and transmitted every 10-30 seconds. The primary servers run in a MS Windows environment with a high-latency, and occasionally intermittent, network connection. Therefore, any application would have to be tolerant of this and ideally automatically reconnect / resend data that could not be transmitted. Due to the environment and the requirements, a full-blown replication package would be unnecessary. I appreciate any help anyone has with this problem.

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• SQL Server - Error when trying to reference a .mdf file

  - by Amokrane

  Hi, For a NUnit test I need to reference a .mdf file from a .config file. Unfortunately, I get the following error message: The FOR ATTACH option requires that at least the primary file be specified. An attempt to attach an auto-named database for file C:\....\*.mdf A database with the same name exists, or specified file cannot be opened, or it is located on UNC share. I looked for this error on google but didn't find anything that helped me solve my problem. Any idea? Thank you

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• How to model my database when using entity framework 4?

  - by Junior Ewing

  Trying to wrap my head around the best approach in modelling a database when we are using Entity Framework 4 as the ORM layer. We are going to use asp.net mvc 2 for the application. Is it worth trying to model using the class diagram modeller that comes with Visual Studio 2010 where you graphically configure your models into the EDMX file and then generate out the database structure? I have run into a bunch of non trivial issues and for complex many to many mappings or multi primary key entities the answer is not that obvious even after poking around a while with the tools. I figure its easy at this point to give up and start modelling the DB using real, working DB modelling tools and then try to generate out the EDMX from the database, rather than trying to do the model first approach.

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• Dynamically determining table name given field name in SQL server

  - by Salman A

  Strange situation: I am trying to remove some hard coding from my code. There is a situation where I have a field, lets say "CityID", and using this information, I want to find out which table contains a primary key called CityID. Logically, you'd say that it's probably a table called "City" but it's not... that table is called "Cities". There are some other inconsistencies in database naming hence I can never be sure if removing the string "ID" and finding out the plural will be sufficient. Note: Once I figure out that CityID refers to a table called Cities, I will perform a join to replace CityID with city name on the fly. I will appreciate if someonw can also tell me how to find out the first varchar field in a table given its name.

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• How do I chain forms in Access? (pass values between them)

  - by jeff porter

  Hello, I'm using Access 2007 and have a data model like this... Passenger - Bookings - Destinations So 1 Passenger can have Many Bookings, each for 1 Destinations. My problem... I can create a form to allow the entry of Passenger details, but I then want to add a NEXT button to take me to a form to enter the details of the Booking (i.e. just a simple drop list of the Destinations). I've added the NEXT button and it has the events of RunCommand SaveRecord OpenForm Destination_form BUT, I cant work out how to pass accross to the new form the primary key of the passenger that was just entered (PassengerID). I'd really like to have just one form, and that allow the entry of the Passenger details and the selection of a Destination, that then creates the entries in the 2 Tables (Passenger & Bookings), but I can't get that to work either. Can anyone help me out please? Thanks Jeff Porter

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• How do you verify the correct data is in a data mart?

  - by blockcipher

  I'm working on a data warehouse and I'm trying to figure out how to best verify that data from our data cleansing (normalized) database makes it into our data marts correctly. I've done some searches, but the results so far talk more about ensuring things like constraints are in place and that you need to do data validation during the ETL process (E.g. dates are valid, etc.). The dimensions were pretty easy as I could easily either leverage the primary key or write a very simple and verifiable query to get the data. The fact tables are more complex. Any thoughts? We're trying to make this very easy for a subject matter export to run a couple queries, see some data from both the data cleansing database and the data marts, and visually compare the two to ensure they are correct.

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• IN statement performance in PostgreSQL (and in general)

  - by Vasil

  I know this has probably been asked before, but I can't find it with SO's search. Lets say i've TABLE1 and TABLE2, who should I expect the performance of a query such as this: SELECT * FROM TABLE1 WHERE id IN SUBQUERY_ON_TABLE2; as the number of rows in TABLE1 and TABLE2 grow and id is a primary key on TABLE1. Yes, I know using IN is such a n00b mistake, but TABLE2 has a generic relation (django generic relation) to multiple other tables so I can't think of another way to filter the data. At what (aproximate) ammount of rows in TABLE1 and TABLE2 should I expect to notice performance issues because of this? Will performance degrade linearly, exponentially etc. depending on the number of rows?

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• Using sizeof operator on a typedef-ed struct

  - by sskanitk

  This might be something too obvious. However, I couldn't find the specific answer though many stackoverflow threads talk about different aspects of this. typedef struct _tmp { unsigned int a; unsigned int b; } tmp; int main() { int c=10; if (c <= sizeof tmp) { printf("less\n"); } else { printf("more\n"); } return 0; } I compile this prog as - g++ -lstdc++ a.cpp I get an error - expected primary-expression before ‘)’ token I think I am missing something very obvious and straightforward. But can't seem to pinpoint it :-/ Thanks!

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• Get the WPMU default blog domain

  - by RobertWHurst

  I have a network of blogs that link to each other. The problem is when I want to get the primary blog's domain. I need it for things like the the target of the logo when clicked. I can't seem to find a function in WPMU the retrieves this. I can see the value I want in the wp_site table. I could easily get it with $wpdb, but its a bit over kill, and if there is a function that can get the value already, then I want to use it.

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• Sqlite3 activerecord :order => "time DESC" doesn't sort

  - by Ole Morten Amundsen

  rails 2.3.4, sqlite3 I'm trying this Production.find(:all, :conditions = ["time ?", start_time.utc], :order = "time DESC", :limit = 100) The condition works perfectly, but I'm having problems with the :order = time DESC. By chance, I discovered that it worked at Heroku (testing with heroku console), which runs PostgreSQL. However, locally, using sqlite3, new entries will be sorted after old ones, no matter what I set time to. Like this (output has been manually stripped): second entry is new: Production id: 2053939460, time: "2010-04-24 23:00:04", created_at: "2010-04-24 23:00:05" Production id: 2053939532, time: "2010-04-25 10:00:00", created_at: "2010-04-27 05:58:30" Production id: 2053939461, time: "2010-04-25 00:00:04", created_at: "2010-04-25 00:00:04" Production id: 2053939463, time: "2010-04-25 01:00:04", created_at: "2010-04-25 01:00:04" Seems like it sorts on the primary key, id, not time. Note that the query works fine on heroku, returning a correctly ordered list! I like sqlite, it's so KISS, I hope you can help me... Any suggestions?

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• Why is autorelease especially dangerous/expensive for iPhone applications?

  - by e.James

  I'm looking for a primary source (or a really good explanation) to back up the claim that the use of autorelease is dangerous or overly expensive when writing software for the iPhone. Several developers make this claim, and I have even heard that Apple does not recommend it, but I have not been able to turn up any concrete sources to back it up. SO references: autorelease-iphone Why does this create a memory leak (iPhone)? Note: I can see, from a conceptual point of view, that autorelease is slightly more expensive than a simple call to release, but I don't think that small penalty is enough to make Apple recommend against it. What's the real story?

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• Java Caching on distributed environment

  - by Naren

  Hi, I am supposed to create a simple replicated cache using java for internal purpose which will be used in a distributed environment. I have seen oracle has implemented Replicated Cache Service. http://wiki.tangosol.com/display/COH32UG/Replicated+Cache+Service The problem I am facing is while doing an update or remove, I acquire lock on other cache's to the point the cache get's updated and notifies others of the change. This is eventually going into a dead lock situation, while removing. Is there any strategy I should follow while updating or removing from cache's. Can I implement a replicated cache without having a primary cache?? Thanks, Naren

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• Best practices or tools for installing a MS SQL database

  - by Maestro1024

  Best practices or tools for installing a MS SQL database I have a MS SQL database designed with the MS SQL GUI database editor/Visual Studio. What is the best way to "install" that database on other systems. Said another way how should I ship this thing? I know I can save the scripts and set the primary/foreign keys with T-SQL but I suspect their is something better. I guess you could have people restore from backup but that does not seem very professional. What other choices are there and what are the pluses and minuses?

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• The most elegant way to encapsulate WinAPI callbacks inside a class

  - by FractalizeR

  Hello. I am thinking about elegant way to encapsulate WinAPI callbacks inside a class. Suppose I am making a class handling asynchronous I/O. All Windows callbacks should be stdcall functions, not class methods (I need to pass their addresses to ReadFileEx WinAPI function for example). So, I cannot just pass method addresses as a callback routines to WinAPI functions. What is the most elegant way to encapsulate functionality of this type inside a class so that the class have events OnReadCompleted and OnWriteCompleted (I am using Delphi as a primary language, but I guess the situation must be the same in C++ because class methods are different from simple methods by the fact, that the first hidden parameter of them is this link. Of course this class is not a singleton and there can be many of them created by app at the same time. What do you think would be the good way to implement this?

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• Does php mvc framework agavi use CRUD compliant to REST?

  - by txwikinger

  The agavi framework uses the PUT request for create and POST for updating information. Usually in REST this is used the other way around (often referring to POST adding information while PUT replacing the whole data record). If I understand it correctly, the important issue is that PUT must be idempotent, while POST does not have this requirement. Therefore, I wounder how creating a new record can be idempotent (i.e. multiple request do not lead to multiple creations of a record) in particular when usually the ORM uses an id as a primary key and the id of a new record would not be known to the client (since it is autocreated in the database), hence cannot be part of the request. How does agavi maintain the requirement of idempotence in light of this for the PUT request. Thanks.

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• What is lisp used for today and where do you think it's going ?

  - by ldigas

  Never been a lisp user, so don't take me as too dense while reading this. But what is lisp used for today ? I know there are several variants of the language in existence, at least one which will keep it alive commercially for a while longer (AutoLisp, VisualLisp - pretty big support from Autodesk) ... but I don't meet everyday people using it. So if you can shed some light on the matter - what is it's primary target market nowadays ? And what do you believe its future will be ... will it become just another support language in few apps, or is it going somewhere ? Also, apart from "an editor whose name shall not be spoken" what other apps keep it as a support language ?

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• mysql query - syntax error - cannot find out why

  - by Phil Jackson

  Hi all, im taring my hair out over this one. A query is throwing an error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM, SUBJECT, DATE, READ, MAIL ) VALUES ( 'EJackson', 'dfdf', '1270974101', 'fa' at line 1 I printed out the query to see what could be the problem: INSERT INTO db.tablename ( FROM, SUBJECT, DATE, READ, MAIL ) VALUES ( 'EJackson', 'dfdf', '1270974299', 'false', 'dfdsfdsfd' ) and finaly the structure consists of: CREATE TABLE db.tablename ( `ID` int(12) NOT NULL auto_increment, `FROM` varchar(255) NOT NULL, `SUBJECT` varchar(255) NOT NULL, `DATE` varchar(255) NOT NULL, `READ` varchar(255) NOT NULL, `MAIL` varchar(255) NOT NULL, PRIMARY KEY (`ID`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ; I cant find anything wrong. Any Help would be much appreciated. ( db.tablename is a replacement for the actual tablename )

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• How do you access byte level information in JavaScript?

  - by JustSmith

  The generally accepted answer is that you can't. However there is mounting evidence that this is not true based on the existence of projects that read in types of data that are not basic HTML types. Some projects that do this are the JavaScript version of ProtoBuf and Smokescreen. Smokescreen is a flash interpreter written in JS so if it is not possible to get at the bytes directly how are these projects working around this? The source to Smokescreen can be found here. I have looked it over but with JS not being my primary language right now the solution eludes me.

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• MySQL get row closest to NOW()

  - by Christopher McCann

  I have a table with User data such as name, address etc and another table which has a paragraph of text about the user. The reason that they are separate is because we need to record all the old about data. So if the user changes their paragraph - the old one should still be stored. Each bit of about data has a primary key aboutMeID. What I want to do is have a join that pulls their name, address etc and the latest bit of aboutMe data from the other table. I am not sure though how I can order the join to only get the latest about me data. Can someone help?

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• Showing all rows for keys with more than one row

  - by Leif Neland

  Table kal id integer primary key init char 4 indexed job char4 id init job --+----+------ 1 | aa | job1 2 | aa | job2 3 | bb | job1 4 | cc | job3 5 | cc | job5 I want to show all rows where init has more than one row id init job --+----+------ 1 | aa | job1 2 | aa | job2 4 | cc | job3 5 | cc | job5 I tried select * from kal where init in (select init from kal group by init having count(init)2); Actually, the table has 60000 rows, and the query was count(init)<40, but it takes humongus time, phpmyadmin and my patience runs out. Both select init from kal group by init having count(init)2) and select * from kal where init in ('aa','bb','cc') runs in "no time", less than 0.02 seconds. I've tried different subqueries, but all takes "infinite" time, more than a few minutes; I've actually never let them finish. Leif

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• How to force restart a Windows box using VBScript?

  - by tloach

  I'm trying to find a way to force Windows to reboot, and I am running into issues. I've tried Set OpSysSet = GetObject("winmgmts:{authenticationlevel=Pkt," _ & "(Shutdown)}").ExecQuery("select * from Win32_OperatingSystem where "_ & "Primary=true") for each OpSys in OpSysSet retVal = OpSys.Reboot() next I've also tried using the shutdown -f -r command, and in both cases I sometimes get no response, and if I try again I get an error saying "Action could not complete because the system is shutting down" even though no matter how long I leave it it doesn't shut down, it still allows me to start new programs, and doing a shutdown -a gives the same error. How can a script be used to force Windows to reboot?

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• How to set up precision attribute used by @Collumn annotation ???

  - by Arthur Ronald F D Garcia

  I often use java.lang.Integer as primary key. Here you can see some piece of code @Entity private class Person { private Integer id; @Id @Column(precision=8, nullable=false) public Integer getId() { } } I need to set up its precision attribute value equal to 8. But, when exporting The schema (Oracle), it does not work as expected. AnnotationConfiguration configuration = new AnnotationConfiguration(); configuration .addAnnotatedClass(Person.class) .setProperty(Environment.DIALECT, "org.hibernate.dialect.OracleDialect") .setProperty(Environment.DRIVER, "oracle.jdbc.driver.OracleDriver"); SchemaExport schema = new SchemaExport(configuration); schema.setOutputFile("schema.sql"); schema.create(true, false); schema.sql outputs create table Person (id number(10,0) not null) Always i get 10. Is There some workaround to get 8 instead of 10 ?

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• Checking for reciprocal relationships in mysql. A trivial one table problem.

  - by calumbrodie

  I have a mysql table that stores relationships. Items can be related to another item in one direction, or both items can be related to each other. I want to return all items related to my primary item - but I also want to check to see if the related item has a 'reverse relationship' to the current item and show this as a boolean |--------------|---------------| | SKU | related_SKU | |--------------|---------------| | 0001 | 0099 | | 0002 | 0099 | | 0099 | 0001 | |--------------|---------------| If I want to get all relationships for SKU=0001 SELECT related_SKU from relationships where SKU='0001' returns |--------------| | related_SKU | |--------------| | 0099 | |--------------| but what I want is |--------------|---------------| | related_SKU | reciprocal | |--------------|---------------| | 0099 | 1 | |--------------|---------------| or SELECT related_SKU from relationships where SKU='0002' |--------------|---------------| | related_SKU | reciprocal | |--------------|---------------| | 0099 | 0 | |--------------|---------------| What's the best way to do this?

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• MySQL Query: Winning Auction Bid

  - by mabwi

  I have a small Bidding system that I'm using for a fantasy auction draft. I'm trying to use the below query to pull up the max bids on each player. However, it's not actually giving me the max bid, it's just giving me the first one entered in to the database. SELECT Bid.id FROM bids AS Bid WHERE Bid.active =1 GROUP BY player_id HAVING MAX( Bid.amount ) Here's the Bid table layout, in case it helps: CREATE TABLE IF NOT EXISTS `bids` ( `id` int(10) NOT NULL AUTO_INCREMENT, `user_id` int(10) NOT NULL, `player_id` int(10) NOT NULL, `amount` int(6) NOT NULL, `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `winning_bid` int(1) NOT NULL DEFAULT '0', `active` int(1) NOT NULL DEFAULT '1', PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 ;

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• SQL GROUP BY with "default values"

  - by Christoph Schiessl

  I'm trying to create SELECT statement with a GROUP BY clause, which should return "default values". Imagine the following simple MySQL table: CREATE TABLE `tracker` ( `id` INTEGER PRIMARY KEY auto_increment, `date` DATETIME NOT NULL, `customer_id` INTEGER NOT NULL ); The table contains only one record: INSERT INTO `tracker` (`date`, `customer_id`) VALUES('2010-05-03', 1); After wards I'm executing the following SQL query: SELECT DATE(`date`), COUNT(customer_id) FROM tracker WHERE DATE(`date`) >= '2010-05-01' AND DATE(`date`) <= '2010-05-05' GROUP BY DATE(`date`) ORDER BY DATE(`date`); And get the expected result set: +----+---------------------+-------------+ | id | date | customer_id | +----+---------------------+-------------+ | 1 | 2010-05-10 00:00:00 | 1 | +----+---------------------+-------------+ However, I would like the result set to look like this: +--------------+--------------------+ | DATE(`date`) | COUNT(customer_id) | +--------------+--------------------+ | 2010-05-01 | 0 | | 2010-05-02 | 0 | | 2010-05-03 | 1 | | 2010-05-04 | 0 | | 2010-05-05 | 0 | +--------------+--------------------+ Is it possible to achieve this behavior?

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