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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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• What algorithm would you use to code a parrot?

  - by Phil H

  A parrot learns the most commonly uttered words and phrases in its vicinity so it can repeat them at inappropriate moments. So how would you create a software version? Assuming it has access to a microphone and can record sound at will, how would you code it without requiring infinite resources? The best I can imagine is to divide the stream using silences in the sound, and then use some pattern recognition to encode each one as a list of tokens, storing new ones as you meet them. Hashing the token sequences and counting occurrences in a database, you could build up a picture of the most frequently uttered phrases. But given the huge variety in phrases, how do you prevent this just becoming a huge list? And the sheer number of pairs to match would surely generate lot of false positives from the combinatorial nature of matching. Would you use a neural net, since that's how a real parrot manages it? Or is there another, cleverer way of matching large-scale patterns in analogue data?

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• problem reading a csv file in python

  - by Hossein

  Hi, I am trying to read a very simple but somehow large(800Mb) csv file using the csv library in python. The delimiter is a single tab and each line consists of some numbers. Each line is a record, and I have 20681 rows in my file. I had some problems during my calculations using this file,it always stops at a certain row. I got suspicious about the number of rows in the file.I used the code below to count the number of row in this file: tfdf_Reader = csv.reader(open('v2-host_tfdf_en.txt'),delimiter=' ') c = 0 for row in tfdf_Reader: c = c + 1 print c To my surprise c is printed with the value of 61722!!! Why is this happening? What am I doing wrong?

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• Get smallest date for each element in access query

  - by skerit

  So I have a table containing different elements and dates. It basically looks like this: actieElement beginDatum 1 1/01/2010 1 1/01/2010 1 10/01/2010 2 1/02/2010 2 3/02/2010 What I now need is the smallest date for every actieElement. I've found a solution using a simple GROUP BY statement, but that way the query loses its scope and you can't change anything anymore. Without the GROUP BY statement I get multiple dates for every actieElement because certain dates are the same. I thought of something like this, but it also does not work as it would give the subquery more then 1 record: SELECT s1.actieElement, s1.begindatum FROM tblActieElementLink AS s1 WHERE (((s1.actieElement)=(SELECT TOP 1 (s2.actieElement) FROM tblActieElementLink s2 WHERE s1.actieElement = s2.actieElement ORDER BY s2.begindatum ASC)));

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• NULL pointer dereference in swiotlb_unmap_sg_attrs() on disk IO

  - by Inductiveload

  I'm getting an error I really don't understand when reading or writing files using a PCIe block device driver. I seem to be hitting an issue in swiotlb_unmap_sg_attrs(), which appears to be doing a NULL dereference of the sg pointer, but I don't know where this is coming from, as the only scatterlist I use myself is allocated as part of the device info structure and persists as long as the driver does. There is a stacktrace to go with the problem. It tends to vary a bit in exact details, but it always crashes in swiotlb_unmap_sq_attrs(). I think it's likely I have a locking issue, as I am not sure how to handle the locks around the IO functions. The lock is already held when the request function is called, I release it before the IO functions themselves are called, as they need an (MSI) IRQ to complete. The IRQ handler updates a "status" value, which the IO function is waiting for. When the IO function returns, I then take the lock back up and return to request queue handling. The crash happens in blk_fetch_request() during the following: if (!__blk_end_request(req, res, bytes)){ printk(KERN_ERR "%s next request\n", DRIVER_NAME); req = blk_fetch_request(q); } else { printk(KERN_ERR "%s same request\n", DRIVER_NAME); } where bytes is updated by the request handler to be the total length of IO (summed length of each scatter-gather segment).

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• Asynchronous SQL Operations

  - by Paul Hatcherian

  I've got a problem I'm not sure how best to solve. I have an application which updates a database in response to ad hoc requests. One request in particular is quite common. The request is an update that by itself is quite simple, but has some complex preconditions. For this request the business layer first requests a set of data from the data layer. The business logic layer evaluated the data from the database and parameters from the request, from this the action to be performed is determined, and the request's response message(s) are created. The business layer now executes the actual update command that is the purpose of the request. This last step is the problem, this command is dependent on the state of the database, which might have changed since the business logic ran. Locking down the data read in this operation across several round-trips to the database doesn't seem like a good idea either. Is there a 'best-practice' way to accomplish something like this? Thanks!

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• Grouping date periods (by number of days) but exclude the weekends?

  - by tonyyeb

  I have a table with start and end dates in. My goal is to have a table that has grouped these dates into how many days the period spans. I thought I had the solution with a simple SQL statement (MS SQL Server 2005) but I want to exclude weekends. SELECT DATEDIFF(D, StartDate, EndDate)+1 AS Days, COUNT(ID) as Count FROM myDateTable GROUP BY DATEDIFF(D, StartDate, EndDate) This gives a record set of: Days Count 1 4 2 2 4 1 7 2 Is this possible to exclude the weekends in the SQL statement and if not can it be done using ASP and a array perhaps?

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• How to make Amazon EC2 not cause SSL invalid error in browser

  - by tadatoshi

  I use SSL certificate for a web site I set up in Amazon EC2 Machine Instance. The SSL certificate is for one domain name, which is not public DNS for the Amazon Machine Instance. The browser always complains the mismatch in the domain name because it compares the domain name of the SSL certificate to the Amazon public DNS. How can I set up not to cause this problem? I tried both domain name forwarding and A Record setting. Maybe it's because I'm not so familiar with Amazon EC2 and I haven't configured domain name correctly. Any help will be greatly appreciated.

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• C# - Erase all property values from a class?

  - by John M

  In a C# Winforms (3.5) application I have added a class that contains many properties (get/set) used to stored values from a 12 form long process. After form 12 I would like wipe out all the property values in the storing class so that the next user won't accidentally record values when starting the process at form 1. Is it possible to erase/destroy/dispose of all property values in a class? My class looks like this: private static int battery; public int Battery { get { return storeInspectionValues.battery; } set { storeInspectionValues.battery = value; } }

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• Store the day of the week and time

  - by bsiddiqui

  I have a two part question about storing day(s) of the week and time in a database. I'm using Rails 4.0, ruby 2.0.0, and postgres. I have certain events and those events have a schedule. For the event Skydiving for example, for example, I might have Tuesday and Wednesday and 3 pm. 1) Is there a way for me to store the the record for Tuesday and Wednesday in one row or do should I have two records? 2) What is the best way to store the day and time? Is there a way to store day of week and time (not datetime) or should these be separate columns? If they should be separate, how would you store day of week? I was thinking of storing them as integer values (0 for Sunday, 1 for Monday, etc) since that's how wday method for the Time class does it. Any suggestions would be super helpful. Thanks!

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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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• Retrieve rows where a value exists within a comma separated list

  - by Klaaz

  I like to reverse this query: SELECT * FROM table WHERE status IN ( option,option1,option2 ); in a query like SELECT * FROM table WHERE status contains ( 'option' ); Where field 'status' column contains (by example): 'option,option1'. When I use SELECT * FROM table WHERE status LIKE '%option%' ); It also selects the rows with a 'status' column that only contains 'option1' Is this possible? example data: id,name,status 1,'test1','option,option1' 2,'test2','option,option2' 3,'test3','option2' 4,'test4','option2,option3' 5,'test5','option' SELECT * FROM table WHERE status contains ( 'option' ); This query should select select record 1,2 and 5. 'status' field type is varchar. The problem is that the status fields contains data that is almost alike, exept from the added number to option. Off course this is a made up example but the real thing has this kind of parameters

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• Fulltext search not returning expected results

  - by Puneet

  I am experimenting with SQL Server full text search. I have a simple Categories table with Id as the primary key: CREATE TABLE [dbo].[Category]( [Id] [int] IDENTITY(1,1) NOT NULL, [CategoryName] [varchar](100) NOT NULL, ) My Query is: SELECT * FROM FREETEXTTABLE (Category, CategoryName, 'music') AS F INNER JOIN Category C ON F.[Key] = C.Id ORDER BY F.Rank DESC This returns me several records with the word music in them, but it does NOT return any record with word ‘musical’. Although, it can be said that the string being searched is not very big and using the LIKE operator will resolve it. I would like to use fulltext search because this simple example is going to be extended to include other tables and fileds.

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• Update query in ado.net

  - by nikhil

  I wanted to update a column in my table, i have written the code it runs fine without any error also it displays the confirmation dialog box but the table is not updated whats wrong with the code. Dim sqlConn As New SqlClient.SqlConnection sqlConn.ConnectionString = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\housingsociety.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True" Try sqlConn.Open() Catch sqlError As Exception MsgBox(sqlError.Message, 0, "Connection Error!") End Try Dim sqlComm As New SqlClient.SqlCommand sqlComm.Connection = sqlConn sqlComm.CommandText = "update committe_member set name = '@name' where name = 'member1'" Dim paramString As New SqlClient.SqlParameter("@name", SqlDbType.VarChar, 50) paramString.Direction = ParameterDirection.Input sqlComm.Parameters.Add(paramString) paramString.Value = TextBox1.Text sqlComm.ExecuteNonQuery() MsgBox("Record Sucessfully Altered", 0, "Confirmation!") sqlConn.Close()

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• how auto submit a session based form?

  - by hd

  i have a form and want to submit it with a script. i'm going to use curl function in php to do it. but the form is not submit directly. it have 3 steps and at the end of each step it store entered value in session variables and at the final steps it insert record to database with the values are read from sessions. it is possible to do auto submit this form using curl or not? what is the best solution for it??

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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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• Using MySQL as a job queue

  - by user237815

  I'd like to use MySQL as a job queue. Multiple machines will be producing and consuming jobs. Jobs need to be scheduled; some may run every hour, some every day, etc. It seems fairly straightforward: for each job, have a "nextFireTime" column, and have worker machines search for the job with the nextFireTime, change the status of the record to "inProcess", and then update the nextFireTime when the job ends. The problem comes in when a worker dies silently. It won't be able to update the nextFireTime or set the status back to "idle". Unfortunately, jobs can be long-running, so a reaper thread that looks for jobs that have been inProcess too long isn't an option. There's no timeout value that would work. Can anyone suggest a design pattern that would properly handle unreliable worker machines?

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• MS Access raise form events programmatically

  - by Eric G

  Is it possible to raise built-in MS Access form events programmatically? I have a feeling it isn't but thought I would check. (I am using Access 2003). For instance, I want to do something like this within a private sub on the form: RaiseEvent Delete(Cancel) and have it trigger the Access.Form delete event -- i.e. without actually deleting a bound record. Note my delete event is not handled by the form itself but by an external class, so I can't simply call Form_Delete(Cancel).

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• What is a good solution to link different tables in Hibernate based on some field value?

  - by serg555

  I have article table and several user tables a_user, b_user, ... with exactly the same structure (but different data). I can't change anything in *_user tables except their table name prefix but can change everything else (user tables contain only user information, there is nothing about article or user_type in them). I need to link article to a user (many-to-one), but user table name is defined by user_type field. For example Article table record: ... user_id="5" user_type="a" means that it is linked to a user with id=5 from a_user table (id 5 is not unique in users scope, each user table can have its id 5). Any suggestions how to handle this situation? How can I map this relation in Hibernate (xml mapping, no annotations) so it will automatically pick up correct user for an article during select/update? How should I map user tables (one or multiple classes?)? I would need to run some queries like this: from Article a where a.userType=:type and a.user.name=:name Thanks.

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• RSpec: in-depth differences between before(:all) and before(:each)

  - by gmile

  Ok, so I've ran into a very strange issue, directly connected with before blocks. I'm doing a integration testing via Watir and RSpec. For a simple test to check if user can perform a login I'm creating a 'user' record in the db by means of factory_girl. So I put the following code: before(:each) do @user = Factory(:user) end if "should perform a login" do # do stuff end In do stuff I call a browser and see how the user tries to login. Unfortunately, somehow he cannot do that — "Username isn't valid". After some investigation I discovered that if I put the code for creating user in before(:all) block, everything magically works. How's that? What's the difference between :all and :each in this context? Also, If I put the code for creating user actually in the test body, it still doesn't work (i.e. user somehow isn't added to the DB or something).

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• T-SQL Getting duplicate rows returned

  - by cBlaine

  The following code section is returning multiple columns for a few records. SELECT a.ClientID,ltrim(rtrim(c.FirstName)) + ' ' + case when c.MiddleName <> '' then ltrim(rtrim(c.MiddleName)) + '. ' else '' end + ltrim(rtrim(c.LastName)) as ClientName, a.MISCode, b.Address, b.City, dbo.ClientGetEnrolledPrograms(CONVERT(int,a.ClientID)) as Abbreviation FROM ClientDetail a JOIN Address b on(a.PersonID = b.PersonID) JOIN Person c on(a.PersonID = c.PersonID) LEFT JOIN ProgramEnrollments d on(d.ClientID = a.ClientID and d.Status = 'Enrolled' and d.HistoricalPKID is null) LEFT JOIN Program e on(d.ProgramID = e.ProgramID and e.HistoricalPKID is null) WHERE a.MichiganWorksData=1 I've isolated the issue to the ProgramEnrollments table. This table holds one-to-many relationships where each ClientID can be enrolled in many programs. So for each program a client is enrolled in, there is a record in the table. The final result set is therefore returning a row for each row in the ProgramEnrollments table based on these joins. I presume my join is the issue but I don't see the problem. Thoughts/Suggestions? Thanks, Chuck

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• ADO.NET DataService Exception

  - by Ravi

  Hi, I am working on C#.Net with ADO.NET Dataservice. I try to update one record to relational tabel, when I reach context.SetLink() I am getting exception("The context is not currently tracking the entity"). I don't know how to solve this problem. My code is specified below. LogNote dbLogNote =logNote; LogSubSession dbLogSubSession = (from p in context.LogSubSession where p.UID == logNote.SubSessionId select p).First<LogSubSession>() as LogSubSession; context.AddToLogNote(dbLogNote); dbLogNote.LogSubSession = dbLogSubSession; context.SetLink(dbLogNote, "LogSubSession", dbLogSubSession); context.SaveChanges(); Here LogSubSession is a primary table and LogNote is a foreign table. I am updating data into foreign table based on primary key table. Thanks

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• threading in Python taking up too much CPU

  - by KevinShaffer

  I wrote a chat program and have a GUI running using Tkinter, and to go and check when new messages have arrived, I create a new thread so Tkinter keeps doing its thing without locking up while the new thread goes and grabs what I need and updates the Tkinter window. This however becomes a huge CPU hog, and my guess is that it has to do somehow with the fact that the Thread is started and never really released when the function is done. Here's the relevant code (it's ugly and not optimized at the moment, but it gets the job done, and itself does not use too much processing power, as when I run it not threaded, it doesn't take up much CPU but it locks up Tkinter) Note: This is inside of a class, hence the extra tab. def interim(self): threading.Thread(target=self.readLog).start() self.after(5000,self.interim) def readLog(self): print 'reading' try: length = len(str(self.readNumber)) f = open('chatlog'+str(myport),'r') temp = f.readline().replace('\n','') while (temp[:length] != str(self.readNumber)) or temp[0] == '<': temp = f.readline().replace('\n','') while temp: if temp[0] != '<': self.updateChat(temp[length:]) self.readNumber +=1 else: self.updateChat(temp) temp = f.readline().replace('\n','') f.close() Is there a way to better manage the threading so I don't consume 100% of the CPU very quickly?

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• wxpython - Running threads sequentially without blocking GUI

  - by ryantmer

  I've got a GUI script with all my wxPython code in it, and a separate testSequences module that has a bunch of tasks that I run based on input from the GUI. The tasks take a long time to complete (from 20 seconds to 3 minutes), so I want to thread them, otherwise the GUI locks up while they're running. I also need them to run one after another, since they all use the same hardware. (My rationale behind threading is simply to prevent the GUI from locking up.) I'd like to have a "Running" message (with varying number of periods after it, i.e. "Running", "Running.", "Running..", etc.) so the user knows that progress is occurring, even though it isn't visible. I'd like this script to run the test sequences in separate threads, but sequentially, so that the second thread won't be created and run until the first is complete. Since this is kind of the opposite of the purpose of threads, I can't really find any information on how to do this... Any help would be greatly appreciated. Thanks in advance! gui.py import testSequences from threading import Thread #wxPython code for setting everything up here... for j in range(5): testThread = Thread(target=testSequences.test1) testThread.start() while testThread.isAlive(): #wait until the previous thread is complete time.sleep(0.5) i = (i+1) % 4 self.status.SetStatusText("Running"+'.'*i) testSequences.py import time def test1(): for i in range(10): print i time.sleep(1) (Obviously this isn't the actual test code, but the idea is the same.)

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• iPhone app -- are plists the way to handle default values and other languages?

  - by d_CFO

  I wrote my first program almost fifty years ago (yes, coding is still a blast, managing big projects with many programmers was not), but my Von Neumann thinking gets in the way. I want to (a) load default values and (b) account for multiple languages more elegantly (?) than 60-plus iterations of NSLocalizedString. Can I park all of this data into what amounts to a record with fields like this: (key value stuff), (tweak-able user prompt / screen name / whatever), (tasteful default), (user-supplied value)? NSUserDefault has worked well so far; Core Data looks like overkill (?), and sql lite, well, where's Oracle when you need it?

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