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• Which would be better? Storing/access data in a local text file, or in a database?

  - by TerranRich

  Basically, I'm still working on a puzzle-related website (micro-site really), and I'm making a tool that lets you input a word pattern (e.g. "r??n") and get all the matching words (in this case: rain, rein, ruin, etc.). Should I store the words in local text files (such as words5.txt, which would have a return-delimited list of 5-letter words), or in a database (such as the table Words5, which would again store 5-letter words)? I'm looking at the problem in terms of data retrieval speeds and CPU server load. I could definitely try it both ways and record the times taken for several runs with both methods, but I'd rather hear it from people who might have had experience with this. Which method is generally better overall?

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• "No row with the given identifier exists" although it DOES exist!

  - by roesslerj

  Hello all! I am using Hibernate and getting Exception in thread "main" org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [<MyDbObject>#271] What is pretty weird about this error is, that the object with the given id exists in the database. I inserted the problematic record in another run of the application. If I access it in the same run (i.e. same hibernate session) there seem to be no problems retrieving the data. Just because it could be a fault of the mapping: public class ProblemClass { @ManyToOne(optional = false) private MyDbObject myDbObject; } public class MyDbObject { @OneToMany(mappedBy = "myDbObject") private List<ProblemClass> problemClasses; } I have absolutely no clue even where to look at. Any hints highly appreciated!

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• Returning multiple datasets from a stored proc in VB

  - by Ryan Stephens

  I have an encrypted SQL Server stored proc that I run with (or the vb .net equivalent code of): declare @p4 nvarchar(100) set @p4=NULL declare @p5 bigint set @p5=NULL exec AA_PAY_BACS_EXPORT_RETRIEVE_S @PS_UserId=N'ADMN', @PS_Department=N'', @PS_PayFrequency=2, @PS_ErrorDescription=@p4 output select @p4, @p5 this returns 2 datasets and the output parameters for the results, the datasets are made up of various table joins etc, one holds the header record and one the detail records. I need to get the 2 datasets into a structure in VB .net (e.g. linq, sqldatareader, typed datasets) so that I can code with them, I don't know what tables any of this comes from and there are alot of them Whooopeee!!! I came close using Linq to SQL and IMultipleResults but got frustrated when I had to recode it every time I made a change to the designer file. My feelings are that there must be a simple way to do this, any ideas?

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• How can I make hundreds of simultaneously running processes communicate with a database through one

  - by Olfan

  Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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• Generate MySQL data dump in SQL from PHP

  - by Álvaro G. Vicario

  I'm writing a PHP script to generate SQL dumps from my database for version control purposes. It already dumps the data structure by means of running the appropriate SHOW CREATE .... query. Now I want to dump data itself but I'm unsure about the best method. My requirements are: I need a record per row Rows must be sorted by primary key SQL must be valid and exact no matter the data type (integers, strings, binary data...) Dumps should be identical when data has not changed I can detect and run mysqldump as external command but that adds an extra system requirement and I need to parse the output in order to remove headers and footers with dump information I don't need (such as server version or dump date). I'd love to keep my script as simple as I can so it can be hold in an standalone file. What are my alternatives?

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• Log Shipped but Won't Update

  - by MooCow

  I'm currently taking the MS SQL 2K5 Admin course at a local college and ran into a problem with the Log Shipping part. My setup is the following: Windows 7 x64 SQL 2005 SP3 2 SQL server instances on the same machine Log Shipping settings: Performed full then log back up of Primary Manually restore on Secondary in STANDBY MODE Insert a new record into the table Set up Log Shipping on Primary using SQL Authenication login to connect to the Secondary Set up timers and copy destination on Secondary Monitoring instance not being used I set up a shared folder for WORKGROUP so both instances on the machine can read & write to it. I can see transaction logs generated and copied as defined by the Transaction Shipping wizard. However, the specified table on the Secondary instance is not updating.

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• Query on Triggers..

  - by RBA

  Created One Trigger in Oracle.. SQL> CREATE OR REPLACE TRIGGER student_after_insert 2 AFTER INSERT 3 ON student 4 FOR EACH ROW 5 BEGIN 6 @hello.pl 9 END student_after_insert; 10 / Contents of hello.pl are:- BEGIN DBMS_OUTPUT.PUT_LINE('hello world'); END; And.. the result is pretty good, as the content of hello.pl is displayed on screen while inserting a record.. Now, the query is -- When i change the content of the hello.pl file, after exiting from oracle, and then logging again, It doesn't shows the updated contents, instead it shows the previous content.. I noticed that, if i drop the trigger and create it again, then it is working fine.. Why is it happening so.. And what is the solution to this problem..

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• Reusing an anonymous parameter in a prepared statement

  - by Chris Lieb

  I am customizing the insert SQL generated by hibernate and have hit an issue. When Hibernate generates the query by itself, it inserts data into the first two columns of the table, but this causes a database error since all four columns of the table are non-nullable. For the insert to be performed properly, it must insert the same data into two columns of the new record. This means that I need Hibernate to bind the same data to two different parameters in the query (prepared statement) that I am writing. Is there some SQL syntax that allows me to refer to anonymous parameters bound to a prepared statement in an order different from which they are bound? Details REF_USER_PAGE_XREF ---------------------------------------- PK FK1 | NETWORK_ID | VARCHAR2(100) PK FK1 | PAGE_PATH | VARCHAR2(1000) | USER_LAST_UPDT | VARCHAR2(100) | TMSP_LAST_UPDT | DATE insert into REF_USER_ROLE_XREF( NETWORK_ID, PAGE_PATH, TMSP_LAST_UPDT, USER_LAST_UPDT) values ( ?, /* want to insert the same data here */ ?, ?, /* and here */ (select to_char(sysdate, 'DD-MON-YY') from dual) I want to insert the same data into the first and third anonymous parameters.

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• How to avoid concurrent execution of a time-consuming task without blocking?

  - by Diego V

  I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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• Null Value Statement

  - by Sam

  Hi All, I have created a table called table1 and it has 4 columns named Name,ID,Description and Date. I have created them like Name varchar(50) null, ID int null,Description varchar(50) null, Date datetime null I have inserted a record into the table1 having ID and Description values. So Now my table1 looks like this: Name ID Description Date Null 1 First Null One of them asked me to modify the table such a way that The columns Name and Date should have Null values instead of Text Null. I don't know what is the difference between those I mean can anyone explain me the difference between these select statements: SELECT * FROM TABLE1 WHERE NAME IS NULL SELECT * FROM TABLE1 WHERE NAME = 'NULL' SELECT * FROM TABLE1 WHERE NAME = ' ' Can anyone explain me?

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• Reading data from a MySQL database into a HTML Table?

  - by Michael McKay

  So i am working on a project and need some advice. I have a MySQL database that stores events, i know how to code this functionality in PHP but im just stuck of a few specifics. As the project that I am creating is a timetable, the most important attributes are the day of the event, starting time and finishing time. Once i have read this data from the MYSQL database using my PHP script, how do i go about inserting these events in to a html timetable? Lets say i have record like below in my events table: Event ID = 01 Event Day = Monday Event Start = 12:00 Event End = 14:00 How would I then put that into a html table, bearing in mind that i may have mutiple events for a day?

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• Multiple conditions with CASE statements

  - by Pavan Reddy

  I need to query some data. here is the query that i have constructed but which isn't workig fine for me. For this example I am using AdventureWorks database. SELECT * FROM [Purchasing].[Vendor] WHERE PurchasingWebServiceURL LIKE case // In this case I need all rows to be returned if @url is '' or 'ALL' or NULL when (@url IS null OR @url = '' OR @url = 'ALL') then ('''%'' AND PurchasingWebServiceURL IS NULL') //I need all records which are blank here including nulls when (@url = 'blank') then (''''' AND PurchasingWebServiceURL IS NULL' ) //n this condition I need all record which are not like a particular value when (@url = 'fail') then ('''%'' AND PurchasingWebServiceURL NOT LIKE ''%treyresearch%''' ) //Else Match the records which are `LIKE` the input value else '%' + @url + '%' end This is not working for me. How can I have multiple where condition clauses in the THEN of the the same CASE? How can I make this work?

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• Is this query safe in SQL Server?

  - by xaw

  I have this SQL update query: UPDATE table1 SET table1.field1 = 1 WHERE table1.id NOT IN (SELECT table2.table1id FROM table2); Other portions of the application can add records to table2 which use the field table1id to reference table1. The goal here is to remove records from table1 which aren't referenced by table2. Does SQL Server automatically lock table2 with this kind of query so that a new record can't be added to table2 while executing this query? I've also considered: UPDATE table1 SET field1 = 1 WHERE 0 = (SELECT COUNT(*) FROM table2 WHERE table1.id = table2.table1id); Which seems possibly safer, but much slower (because a SELECT would be called on each row of table1 instead of just one select for the NOT IN)

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• I need to simplify a MySQL sub query for performance - please help

  - by Richard

  I have the following query which is takin 3 seconds on a table of 1500 rows, does someone know how to simplify it? SELECT dealers.name, dealers.companyName, dealer_accounts.balance FROM dealers INNER JOIN dealer_accounts ON dealers.id = dealer_accounts.dealer_id WHERE dealer_accounts.id = ( SELECT id FROM dealer_accounts WHERE dealer_accounts.dealer_id = dealers.id AND dealer_accounts.date < '2010-03-30' ORDER BY dealer_accounts.date DESC, dealer_accounts.id DESC LIMIT 1 ) ORDER BY dealers.name I need the latest dealer_accounts record for each dealer by a certain date with the join on the dealer_id field on the dealer_accounts table. This really should be simple, I don't know why I am struggling to find something.

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• What to do with twitter oauth token once retreived?

  - by mcintyre321

  I'm writing a web app that will use twitter as its primary log on method. I've written code which gets the oauth token back from Twitter. My plan is now to Find the entry in my Users table for the twitter username retreived using the token, or create the entry if necessary Update the Users.TwitterOAuthToken column with the new OAuth token Create a permanent cookie with a random guid on the site and insert a record into my UserCookies table matching Cookie to User when a request comes in I will look for the browser cookie id in the UserCookies table, then use that to figure out the user, and make twitter requests on their behalf Write the oauth token into some pages as a js variable so that javascript can make requests on behalf of the user If the user clears his/her cookies the user will have to log in again to twitter Is this the correct process? Have I created any massive security holes? thanks!

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• I'm having a hard time wrapping my head around handling the Activity Lifecycle...

  - by kefs

  So it seems i've created a fatal flaw and coded an app before understanding/handling rotation/lifecycle events.. Currently, all of my code is in onCreate of each activity. I've read a lot of lifecycle tutorials online, including the official dev guide info, but i'm still having an almost unbelievably hard time trying to wrap my head around the rotation/lifecycle events/methods and when to use them correctly. For example, my app currently has an activity that opens the db, inserts a record, then closes the db.. if i rotate my screen on this activity, the data is re-entered into the db. Using the available lifecycle events (onPause(), onResume(), etc..), how would I prevent this db call from happening again? Would I have to pass a variable through the state saying that the db call has been done, and not to do it again? Thanks in advance..

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• Violation of primary key constraint, multiple users

  - by MC.

  Lets say UserA and UserB both have an application open and are working with the same type of data. UserA inserts a record into the table with value 10 (PrimaryKey='A'), UserB does not currently see the value UserA entered and attempts to insert a new value of 20 (PrimaryKey='A'). What I wanted in this situation was a DBConcurrencyException, but instead what I have is a primary key violation. I understand why, but I have no idea how to resolve this. What is a good practice to deal with such a circumstance? I do not want to merge before updating the database because I want an error to inform the user that multiple users updated this data.

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• Setting parameters after obtaining their values in stored procedures

  - by user1260028

  Right now I have an upload field while uploads files to the server. The prefix is saved so that it can later be obtained for retrieval. For this I need to attach the ID of the form to the prefix. I would like to be able to do this as such: @filePrefix = SCOPE_IDENTITY() + @filePrefix; However I am not so sure this would work because the record has not been created yet. If anything I could call an update function which obtains the ID and then injects it into the row after it has been created. To speed things up, I don't want to do this on the server but rather do this on the database. Regardless of what the approach is, I would still like to know if something like the above is possible (at least for future reference?) So if we replace that with @filePrefix = 5 + @filePrefix; would that be possible? SQL doesn't seem to like the current syntax very much...

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• Caching result of SELECT statement for reuse in multiple queries

  - by Andrew

  I have a reasonably complex query to extract the Id field of the results I am interested in based on parameters entered by the user. After extracting the relevant Ids I am using the resulting set of Ids several times, in separate queries, to extract the actual output record sets I want (by joining to other tables, using aggregate functions, etc). I would like to avoid running the initial query separately for every set of results I want to return. I imagine my situation is a common pattern so I am interested in what the best approach is. The database is in MS SQL Server and I am using .NET 3.5.

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• SQL 2008 GUID column is all 0's

  - by Andy Evans

  I'm hoping this is a simple goof I did on my end ... I have a table in my database set up like so: column name: widget_guid data type: uniqueidentifier allow nulls: false default value: newid() identity: false row guid: true When records are created (via LINQ to SQL) that the values in this field are formatted as a GUID but contain all 0's My assumption was that when a new record was created, that a guid would be autogenerated for that column, much like an auto-incrementing row id. Is this not true? Any help would be greatly appreciated. Thanks.

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• Insert using stored procedure from nhibernate

  - by jcreddy

  Hi I am using the following code snippets to insert values using stored procedure. the code is executing successfully but no record is inserted in DB. Please suggest with simple example. **---- stored procedure--------** Create PROCEDURE [dbo].[SampleInsert] @id int, @name varchar(50) AS BEGIN insert into test (id, name) values (@id, @name); END **------.hbm file-------** <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"> <sql-query name="Procedure"> exec SampleInsert :Id,:Name </sql-query> </hibernate-mapping> **--------c# code to insert value using above sp------** ISessionFactory sessionFactory = new Configuration().Configure().BuildSessionFactory(); ISession session = sessionFactory.OpenSession(); IQuery query = session.GetNamedQuery("Procedure"); query.SetParameter("Id", "222"); query.SetParameter("Name", "testsp"); query.SetResultTransformer(new NHibernate.Transform.AliasToBeanConstructorResultTransformer(typeof(Procedure).GetConstructors()[0])); Regards Jcreddy

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• django updating m2m field

  - by Marconi

  I have a model service and a ModelForm named Service which I use to add and update the service model. The model looks like this: class Service(models.Model): categories = models.ManyToManyField(Category) The categories field is displayed as a tag with that allows multiple selection. It works well when I'm adding a new record but when I'm updating it, only one service is showing up on the request.POST['categories'] even if I selected multiple categories. I tried dumping the request object and I can see that the categories is showing something like: u'categories': [u'3', u'4', u'2'] I tried calling the request._get_post() and it did return only 1 category, hence the request.POST['categories'] returns only 1. Anybody who knows what's happening and how to fix it?

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• Linq To Sql Entity Updated from Trigger

  - by James Helms

  I have a Table called Address. I have a Trigger for insert on that table that does some spacial calculations on the address that determines what neighborhood boundaries it is in. address = new Address { Street = this.Street, City = this.City, State = this.State, ZipCode = this.ZipCode, latitude = this.Latitude, longitude = this.Longitude, YearBuilt = this.YearBuilt, LotSize = this.LotSize, FinishedSize = this.FinishedSize, Bedrooms = this.Bedrooms, Bathrooms = this.Bathrooms, UseCode = this.UseCode, HOA = this.HOA, UpdateDate = DateTime.Now }; db.AddToAddresses(address); db.SaveChanges(); In the database i can clearly see that the Trigger ran and updated the neighborhoodID in the address table for the row. I tried to just reload that record to get the assigned id like this: address = (from a in db.Addresses where a.AddressID == address.AddressID select a).First(); In the debugger i can clearly see that the address.AddressID is correct, entity doesn't update in memory. Is there any work around for this?

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• Need Insight - What is the best practice for syncing up a production database that will be used on a

  - by james

  I have a site set up using CakePHP and MySQL and I want to work on a test database without disrupting my live site in case something goes wrong. I have another busy site, but my test site runs off the live database which can be occasionally nerve wracking. What do I do if I change a table name in the test db and I want it changed in the live database? Or if I remove a record from the test database. Is there a way to diff the changes? How do I even merge those changes? How does this interfere with live user edits and things of that nature? Hopefully some of you working devs can share some insight!

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• Using Linq, how to separate a list in to grouped objects by name?

  - by Dr. Zim

  I have a table where a record looks like this varchar(255) Name varchar(255) Text varchar(255) Value Name is the DDL name, Text is what is displayed, and Value is returned upon selection. There are between one and twenty options for each Name. Without iterating though each option like a cursor, is there any way to pull out a list of objects, one for each unique DDL Name, using Linq and C#? A sample of the data: Beds '4 (10)' 4 Beds '5 (1)' 5 Beds '7 (1)' 7 Baths 'NA (13)' NULL Baths '0 (1)' 0 Baths '1 (13)' 1 I was thinking about doing an outer select to get the unique Names, then an inner select to get the list of options for it, then return the set as a List of a set of Lists.

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