Search Results

Search found 19425 results on 777 pages for 'output clause'.

Page 254/777 | < Previous Page | 250 251 252 253 254 255 256 257 258 259 260 261  | Next Page >

  • Occasional conversion error using SUM function

    - by user153777
    My app uses sql2000 and a select statement it uses will sometimes fail. Once a week or so the select returns the error 'Error Converting data type varchar to numeric' SQL: sum(case when ISNULL(form_prsn_id, -1) = irpd_prsn_id then convert(dec(11,2), case when valu_value = '' then '0' else isnull (valu_value,'0') end)* case when fmdt_deduction_flag = 'Y' then -1 else 1 end else 0 end) as client_sum The valu_value field is a varchar and stores some numeric and some varchar. But including my join and where clause filter it will always select numeric or empty string. When it is failing I can remove the SUM, see the data and know that its numeric. So why would the SUM function sometimes (say 5% of time) fail on data that is numeric. I wonder if SQL somehow "looks ahead" to ensure it could convert to decimal on more than just the rows returned without the sum. Note I have discovered a fix where I include ( where isNumeric(valu_value) = 1 ) Thanks

    Read the article

  • 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

    Read the article

  • Oracle ORA-01795 error in Rails

    - by Cyborgo
    Hi, I am using Oracle as database for my Rails applications and have got some pretty intense tables. I'm trying to find the particular entries using a query like this Author.all( :conditions => { :name => names } ) I have been working SQlite all along and just migrated to Oracle which complains that IN clause has more than 1000 entries. Obvious workaround would be to break it into subclauses for which I need to write some raw sql queries. Is there anything in Rails that facilitate this?

    Read the article

  • MySQL GROUP BY with three tables

    - by Psaniko
    I have the following tables: posts (post_id, content, etc) comments (comment_id, post_id, content, etc) posts_categories (post_category_id, post_id, category_id) and this query: SELECT `p`.*, COUNT(comments.comment_id) AS cmts, posts_categories.*,comments.* FROM `posts` AS `p` LEFT JOIN `posts_categories` ON `p`.post_id = `posts_categories`.post_id LEFT JOIN `comments` ON `p`.post_id = `comments`.post_id GROUP BY `p`.`post_id` There are three comments on post_id=1 and four in total. In posts_categories there are two rows, both assigned to post_id=1. I have four rows in posts. But if I query the statement above I get a result of 6 for COUNT(comments.comment_id) at post_id=1. How is this possible? I guess the mistake is somewhere in the GROUP BY clause but I can't figure out where. Any suggestions?

    Read the article

  • Dynamic "WHERE IN" on IQueryable (linq to SQL)

    - by user320235
    I have a LINQ to SQL query returning rows from a table into an IQueryable object. IQueryable<MyClass> items = from table in DBContext.MyTable select new MyClass { ID = table.ID, Col1 = table.Col1, Col2 = table.Col2 } I then want to perform a SQL "WHERE ... IN ...." query on the results. This works fine using the following. (return results with id's ID1 ID2 or ID3) sQuery = "ID1,ID2,ID3"; string[] aSearch = sQuery.Split(','); items = items.Where(i => aSearch.Contains(i.ID)); What I would like to be able to do, is perform the same operation, but not have to specify the i.ID part. So if I have the string of the field name I want to apply the "WHERE IN" clause to, how can I use this in the .Contains() method?

    Read the article

  • Does the order of the columns in a SELECT statement make a difference?

    - by Frank Computer
    This question was inspired by a previous question posted on SO, "Does the order of the WHERE clause make a differnece?". Would it improve a SELECT statement's performance if the the columns used in the WHERE section are placed at the begining of the SELECT statement? example: SELECT customer.id, transaction.id, transaction.efective_date, transaction.a, [...] FROM customer, transaction WHERE customer.id = transaction.id; I do know that limiting the list of columns to only the needed ones in a SELECT statement improves performance as opposed to using SELECT * because the current list is smaller.

    Read the article

  • what's the name of this language that description another language syntax?

    - by Boolean
    for example: <SELECT statement> ::= [WITH <common_table_expression> [,...n]] <query_expression> [ ORDER BY { order_by_expression | column_position [ ASC | DESC ] } [ ,...n ] ] [ COMPUTE { { AVG | COUNT | MAX | MIN | SUM } ( expression ) } [ ,...n ] [ BY expression [ ,...n ] ] ] [ <FOR Clause>] [ OPTION ( <query_hint> [ ,...n ] ) ] <query_expression> ::= { <query_specification> | ( <query_expression> ) } [ { UNION [ ALL ] | EXCEPT | INTERSECT } <query_specification> | ( <query_expression> ) [...n ] ] <query_specification> ::= SELECT [ ALL | DISTINCT ] [TOP expression [PERCENT] [ WITH TIES ] ] < select_list > [ INTO new_table ] [ FROM { <table_source> } [ ,...n ] ] [ WHERE <search_condition> ] [ <GROUP BY> ] [ HAVING < search_condition > ] whats the language called?

    Read the article

  • :from parameter in active record find not well designed?

    - by potlee
    i got this error: SQLite3::SQLException: no such column: apis.name: SELECT * FROM examples WHERE ("apis"."name" = 'deep') my code Api.find :all, :from => params[:table_name], :conditions => {:name => 'deep' } I need to make a back end rails application which will be used by a silverlight application. one of the requirements is to fetch simple data from the database. i need to be able to query different tables with the same code.(my app has 2000 tables!) i think it does not make sense for rails to put in "apis" in the WHERE clause. is there any speciic reason for this?

    Read the article

  • How can I sum a group of sums? SQL-Sever 2008

    - by billynomates
    I have a query with a sum in it like this: SELECT Table1.ID, SUM(Table2.[Number1] + Table2.[Number2]) AS SumColumn FROM Table1 INNER JOIN Table3 ON Table1.ID = Table3.ID INNER JOIN Table2 ON Table3.ID = Table2.ID WHERE (Table2.[Something] = 'Whatever') GROUP BY Table1.ID, Table2.[Number1] , Table2.[Number2] and it gives me a table like this: ID SumColumn 67 1 67 4 70 2 70 6 70 3 70 6 80 5 97 1 97 3 How can I make it give me a table like this, where the SumColumn is summed, grouped by the ID column? ID SumColumn 67 5 70 17 80 5 97 4 I cannot GROUP BY SumColumn because I get an error (Invalid column name 'SumColumn'.) COALESCE doesn't work either. Thanks in advance. EDIT: Just grouping by the ID gives me an error: [Number1, Number2 and the other column names that I'm selecting] is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

    Read the article

  • Any way for linq query to check against existing select?

    - by danrhul
    I have an an offer, that can be in any number of categories. I don't however want that offer to then appear twice or however more. I was wondering if its possible to have a where clause that ascertains whether that offer already exists in that select statement and if so obviously to ignore it. Here is the linq query: Offers = from o in offerCategories orderby o.RewardCategory.Ordering, o.Order where o.RewardOffer.IsDeleted == false select new OfferOverviewViewModel { Partner = o.RewardOffer.Partner, Description = String.Format("{0} {1}", o.RewardOffer.MainTitle, o.RewardOffer.SecondaryTitle), OfferId = o.OfferId, FeaturedOffer = o.RewardOffer.FeaturedOfferOrder.HasValue, Categories = from c in offerCategories.Where(oc => oc.OfferId == o.OfferId) orderby c.RewardCategory.Ordering select new CategoryDetailViewModel { Description = c.RewardCategory.DisplayName } },

    Read the article

  • compare date split across colums

    - by alex-tech
    Greetings. I am querying tables from Microsoft SQL 2008 which have date split across 3 columns: day, month and year. Unfortunately, I do not have control over this because data is coming in to the database daily from a 3rd party source in that format. I need to add between to a where clause so user can pull records within a range. Would be easy enough if date was in a single column but finding it nearly impossible when its split across three columns. To display the date, I am doing a CAST( CAST(year as varchar(4)) + '-' + CAST(month as varchar(2)) + '-' + CAST(day as varchar(2)) as date) AS "date"` in a select. I tried to put it as a parameter for datediff function or just the regular between but get no results. Thanks for any help.

    Read the article

  • Why does var evaluate to System.Object in "foreach (var row in table.Rows)"?

    - by DanM
    When I enter this foreach statement... foreach (var row in table.Rows) ...the tooltip for var says class System.Object I'm confused why it's not class System.Data.DataRow. (In case you're wondering, yes, I have using System.Data at the top of my code file.) If I declare the type explicitly, as in... foreach (DataRow row in table.Rows) ...it works fine with no errors. Also if I do... var numbers = new int[] { 1, 2, 3 }; foreach (var number in numbers) ...var evaluates to struct System.Int32. So, the problem is not that var doesn't work in a foreach clause. So, there's something strange about DataRowCollection where the items don't automatically evaluate to DataRow. But I can't figure out what it is. Does anyone have an explanation?

    Read the article

  • where clausule on field defined by sub-query

    - by stUrb
    I have this query which displays some properties and count the number of references to it from an other table: SELECT p.id,p.propName ( SELECT COUNT(*) FROM propLoc WHERE propLoc.propID = p.id ) AS number FROM property as p WHERE p.category != 'natural' This generates a good table with all the information I want to filter: id | propName | number 3 | Name 1 | 3 4 | Name 2 | 1 5 | Name 3 | 0 6 | Name 4 | 10 etc etc I now want to filter out the properties with number <= 0 So I tried to add an AND number > 0 But it reacts with Unknown column 'number' in 'where clause' apparently you can't filter on a name specified by a subquery? How can I achieve my goal?

    Read the article

  • Serialization of a TChan String

    - by J Fritsch
    I have declared the following type KEY = (IPv4, Integer) type TPSQ = TVar (PSQ.PSQ KEY POSIXTime) type TMap = TVar (Map.Map KEY [String]) data Qcfg = Qcfg { qthresh :: Int, tdelay :: Rational, cwpsq :: TPSQ, cwmap :: TMap, cw chan :: TChan String } deriving (Show) and would like this to be serializable in a sense that Qcfg can either be written to disk or be sent over the network. When I compile this I get the error No instances for (Show TMap, Show TPSQ, Show (TChan String)) arising from the 'deriving' clause of a data type declaration Possible fix: add instance declarations for (Show TMap, Show TPSQ, Show (TChan String)) or use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (Show Qcfg) I am now not quite sure whether there is a chance at all to serialize my TChan although all individual nodes in it are members of the show class. For TMap and TPSQ I wonder whether there are ways to show the values in the TVar directly (because it does not get changed, so there should no need to lock it) without having to declare an instance that does a readTVar ?

    Read the article

  • Optimizing MySQL queries with IN operator

    - by Arkadiusz Kondas
    I have a MySQL database with a fairly large table where the products are. Each of them has its own id and categoryId field where there is a category id belongs to this product. Now I have a query that pulls out products from given categories such as: SELECT * FROM products WHERE categoryId IN ( 1, 2, 3, 4, 5, 34, 6, 7, 8, 9, 10, 11, 12 ) Of course, come a WHERE clause and ORDER BY sort but not in this thing. Let's say that these products is 250k and the visits are over 100k per day. Under such conditions in the table slow_log registered weight of these queries with large generation time. Do you have any ideas how to optimize the given problem? Table engine is MyISAM.

    Read the article

  • Why do these seemingly similar queries have such drastically different run times?

    - by Jherico
    I'm working with an oracle DB trying to tune some queries and I'm having trouble understanding why working a particular clause in a particular way has such a drastic impact on the query performance. Here is a performant version of the query I'm doing select * from ( select a.*, rownum rn from ( select * from table_foo ) a where rownum < 3 ) where rn >= 2 The same query by replacing the last two lines with this ) a where rownum >=2 rownum < 3 ) performs horribly. Several orders of magnitude worse ) a where rownum between 2 and 3 ) also performs horribly. I don't understand the magic from the first query and how to apply it to further similar queries.

    Read the article

  • With a SELECT...WHERE id IN (...), order results by IN() ?

    - by Deca
    With a query such as: SELECT * FROM images WHERE id IN (12,9,15,3,1) is it possible to order the results by the contents of the IN clause? The result I'm looking for would be something like: [0] => Array ( [id] => 12 [file_name] => foo ) [1] => Array ( [id] => 9 [file_name] => bar ) [2] => Array ( [id] => 15 [file_name] => baz ) ...

    Read the article

  • Outer select column value in joined subquery?

    - by Michael DePetrillo
    Is it possible to use a column value from an outer select within a joined subquery? SELECT table1.id, table2.cnt FROM table1 LEFT JOIN (SELECT COUNT(*) as `cnt` FROM table2 where table2.lt > table1.lt and table2.rt < table1.rt) as table2 ON 1; This results in "Unknown column 'table1.lt' in 'where clause'". Here is the db dump. CREATE TABLE IF NOT EXISTS `table1` ( `id` int(1) NOT NULL, `lt` int(1) NOT NULL, `rt` int(4) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1; CREATE TABLE IF NOT EXISTS `table2` ( `id` int(1) NOT NULL, `lt` int(1) NOT NULL, `rt` int(4) NOT NULL) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `table1` (`id`, `lt`, `rt`) VALUES (1, 1, 4); INSERT INTO `table2` (`id`, `lt`, `rt`) VALUES (2, 2, 3);

    Read the article

  • Count, inner join

    - by Urosh
    I have two tables: DRIVER (Driver_Id,First name,Last name,...) PARTICIPANT IN CAR ACCIDENT (Participant_Id,Driver_Id-foreign key,responsibility-yes or no,...) Now, I need to find out which driver participated in accident where responsibility is 'YES', and how many times. I did this: Select Driver_ID, COUNT (Participant.Driver_ID)as 'Number of accidents' from Participant in car accident where responsibility='YES' group by Driver_ID order by COUNT (Participant.Driver_ID) desc But, I need to add drivers first and last name from the first table(using inner join, I suppose). I don't know how, because it is not contained in either an aggregate function or the GROUP BY clause. Please help :)

    Read the article

  • Update multiple values in a single statement

    - by Kluge
    I have a master / detail table and want to update some summary values in the master table against the detail table. I know I can update them like this: update MasterTbl set TotalX = (select sum(X) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID) update MasterTbl set TotalY = (select sum(Y) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID) update MasterTbl set TotalZ = (select sum(Z) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID) But, I'd like to do it in a single statement, something like this: update MasterTbl set TotalX = sum(DetailTbl.X), TotalY = sum(DetailTbl.Y), TotalZ = sum(DetailTbl.Z) from DetailTbl where DetailTbl.MasterID = MasterTbl.ID group by MasterID but that doesn't work. I've also tried versions that omit the "group by" clause. I'm not sure whether I'm bumping up against the limits of my particular database (Advantage), or the limits of my SQL. Probably the latter. Can anyone help?

    Read the article

  • String path validation

    - by CMAñora
    I have here a string(an input from the user) for a file path. I checked the string so that it will qualify the criteria: check for invalid characters for a file path will not accept absolute path (\Sample\text.txt) I have tried catching the invalid characters in catch clause. It work except for '\'. It will accept 'C:\\Sample\text.txt' which is an invalid file path. The following examples should be invalid paths: :\text.txt :text.txt \:text.txt \text.txt C:\\\text.txt I have been through similar questions posted here but none of them seemed to solve my issue. What would be the best way to do such check?

    Read the article

  • Many to Many Logic in ASP.NET MVC

    - by Jonathan Stowell
    Hi All, I will restrict this to the three tables I am trying to work with Problem, Communications, and ProbComms. The scenario is that a Student may have many Problems concurrently which may affect their studies. Lecturers may have future communications with a student after an initial problem is logged, however as a Student may have multiple Problems the Lecturer may decide that the discussion they had is related to more than one Problem. Here is a screenshot of the LINQ representation of my DB: LINQ Screenshot At the moment in my StudentController I have a StudentFormViewModel Class: // //ViewModel Class public class StudentFormViewModel { IProbCommRepository probCommRepository; // Properties public Student Student { get; private set; } public IEnumerable<ProbComm> ProbComm { get; private set; } // // Dependency Injection enabled constructors public StudentFormViewModel(Student student, IEnumerable<ProbComm> probComm) : this(new ProbCommRepository()) { this.Student = student; this.ProbComm = probComm; } public StudentFormViewModel(IProbCommRepository pRepository) { probCommRepository = pRepository; } } When I go to the Students Detail Page this runs: public ActionResult Details(string id) { StudentFormViewModel viewdata = new StudentFormViewModel(studentRepository.GetStudent(id), probCommRepository.FindAllProblemComms(id)); if (viewdata == null) return View("NotFound"); else return View(viewdata); } The GetStudent works fine and returns an instance of the student to output on the page, below the student I output all problems logged against them, but underneath these problems I want to show the communications related to the Problem. The LINQ I am using for ProbComms is This is located in the Model class ProbCommRepository, and accessed via a IProbCommRepository interface: public IQueryable<ProbComm> FindAllProblemComms(string studentEmail) { return (from p in db.ProbComms where p.Problem.StudentEmail.Equals(studentEmail) orderby p.Problem.ProblemDateTime select p); } However for example if I have this data in the ProbComms table: ProblemID CommunicationID 1 1 1 2 The query returns two rows so I assume I somehow have to groupby Problem or ProblemID but I am not too sure how to do this with the way I have built things as the return type has to be ProbComm for the query as thats what Model class its located in. When it comes to the view the Details.aspx calls two partial views each passing the relevant view data through, StudentDetails works fine page: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<MitigatingCircumstances.Controllers.StudentFormViewModel>" %> <% Html.RenderPartial("StudentDetails", this.ViewData.Model.Student); %> <% Html.RenderPartial("StudentProblems", this.ViewData.Model.ProbComm); %> StudentProblems uses a foreach loop to loop through records in the Model and I am trying another foreach loop to output the communication details: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<IEnumerable<MitigatingCircumstances.Models.ProbComm>>" %> <script type="text/javascript" language="javascript"> $(document).ready(function() { $("DIV.ContainerPanel > DIV.collapsePanelHeader > DIV.ArrowExpand").toggle( function() { $(this).parent().next("div.Content").show("slow"); $(this).attr("class", "ArrowClose"); }, function() { $(this).parent().next("div.Content").hide("slow"); $(this).attr("class", "ArrowExpand"); }); }); </script> <div class="studentProblems"> <% var i = 0; foreach (var item in Model) { %> <div id="ContainerPanel<%= i = i + 1 %>" class="ContainerPanel"> <div id="header<%= i = i + 1 %>" class="collapsePanelHeader"> <div id="dvHeaderText<%= i = i + 1 %>" class="HeaderContent"><%= Html.Encode(String.Format("{0:dd/MM/yyyy}", item.Problem.ProblemDateTime))%></div> <div id="dvArrow<%= i = i + 1 %>" class="ArrowExpand"></div> </div> <div id="dvContent<%= i = i + 1 %>" class="Content" style="display: none"> <p> Type: <%= Html.Encode(item.Problem.CommunicationType.TypeName) %> </p> <p> Problem Outline: <%= Html.Encode(item.Problem.ProblemOutline)%> </p> <p> Mitigating Circumstance Form: <%= Html.Encode(item.Problem.MCF)%> </p> <p> Mitigating Circumstance Level: <%= Html.Encode(item.Problem.MitigatingCircumstanceLevel.MCLevel)%> </p> <p> Absent From: <%= Html.Encode(String.Format("{0:g}", item.Problem.AbsentFrom))%> </p> <p> Absent Until: <%= Html.Encode(String.Format("{0:g}", item.Problem.AbsentUntil))%> </p> <p> Requested Follow Up: <%= Html.Encode(String.Format("{0:g}", item.Problem.RequestedFollowUp))%> </p> <p>Problem Communications</p> <% foreach (var comm in Model) { %> <p> <% if (item.Problem.ProblemID == comm.ProblemID) { %> <%= Html.Encode(comm.ProblemCommunication.CommunicationOutline)%> <% } %> </p> <% } %> </div> </div> <br /> <% } %> </div> The issue is that using the example data before the Model has two records for the same problem as there are two communications for that problem, therefore duplicating the output. Any help with this would be gratefully appreciated. Thanks, Jon

    Read the article

  • Implementing an async "read all currently available data from stream" operation

    - by Jon
    I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a console's standard output Stream. Console output streams are of type FileStream; the implementation can cast to that, if needed. There is also an associated StreamReader already present to leverage. There is only one thing I need to implement in this class to achieve my desired functionality: an async "read all the data available this moment" operation. Reading to the end of the stream is not viable because the stream will not end unless the process closes the console output handle, and it will not do that because it is interactive and expecting input before continuing. I will be using that hypothetical async operation to implement event-based notification, which will be more convenient for my callers. The public interface of the class is this: public class ConsoleAutomator { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Remember that the goal here is to read all of the chunk and call event subscribers exactly once for each chunk. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream. private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer (in which case we know that there was no more data to be read during the last read operation), all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Never more than one event for each time data is available to be read Is almost agnostic to the buffer size The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this. Update: I definitely did not communicate the scenario well in my initial writeup. I have since revised the writeup quite a bit, but to be extra sure: The question is about how to implement an async "read all the data available this moment" operation. My apologies to the people who took the time to read and answer without me making my intent clear enough.

    Read the article

  • problem solving [closed]

    - by Suresh S
    Problem Statement The Sports Associations in India (SAI) wants to choose 2 teams of 4 people each to send to Asian games. There are 13 people who want to be members of the teams. The SAI tries grouping them in various ways to see which athletes perform well together. Each grouping gets one test run on the test track and their time is recorded. Your task is to help the SAI choose two disjoint teams of 4 such that the sum of their practice times is minimal. Input There will be several input instances. The first line of each instance gives the total number of practice runs. This will be followed by n lines. Each of those lines will contain 5 numbers: p1 p2 p3 p4 t t is the time taken (in milliseconds) by the team consisting of p1, p2, p3 and p4. The time taken will not be more than 2 minutes. The end of the input will be indicated by a line with n=0. Output Output the best total and the two teams that you choose. If it is impossible to choose two disjoint teams from the test runs given, output -1. Sample Input 6 1 2 3 4 30000 10 11 12 13 15000 5 6 7 8 37800 1 5 10 12 20000 5 6 9 11 43000 1 9 12 13 11000 3 1 4 7 9 10000 3 5 7 11 17890 6 7 12 13 20000 0 Sample Output 45000 -1 Input to the problem 40 2 8 11 9 15532 1 13 11 9 57629 10 12 1 5 43406 6 10 1 2 43904 8 3 4 11 12473 6 12 5 11 19826 3 9 10 11 48347 6 12 13 1 45854 5 4 9 7 34452 9 8 12 2 5596 4 10 2 7 6778 3 6 8 5 32858 13 12 8 6 42457 12 9 2 5 49530 6 8 10 7 51453 1 3 11 9 18620 6 2 5 11 5153 4 1 9 8 37336 10 5 1 12 59524 4 5 3 2 1318 2 13 6 8 7839 12 4 9 5 30697 4 10 13 1 25249 4 2 9 13 52359 8 11 1 9 36437 7 5 11 6 58522 9 1 12 6 58837 7 6 8 5 37826 13 1 11 3 1841 11 3 5 13 50000 2 8 7 12 10137 1 4 12 5 32558 8 5 6 7 39021 1 7 10 13 5979 9 2 11 6 29661 13 12 9 7 7219 12 1 11 9 37354 5 1 10 9 47948 8 1 2 10 11071 2 11 1 8 3074 80 3 5 8 10 37873 1 2 3 5 27633 10 13 3 11 8645 13 1 9 6 2167 5 11 13 8 30862 8 7 9 6 47591 3 11 13 8 33823 2 13 7 5 36668 12 3 11 6 53711 6 13 3 7 52412 3 6 7 5 3850 1 5 11 12 35483 1 7 6 10 50943 11 3 6 8 40191 12 8 13 7 4529 4 10 5 1 43280 4 12 10 5 35142 12 4 5 10 37242 9 7 13 2 2661 3 9 2 10 453 3 8 12 9 12479 3 10 11 5 30047 9 1 11 2 40883 6 5 1 2 8774 11 7 9 1 37701 8 3 4 6 32970 4 12 7 10 55109 8 11 13 12 44713 2 10 8 5 37763 13 10 12 2 53628 7 2 5 10 53197 3 2 1 11 14916 1 2 3 10 50756 3 13 5 6 6959 10 6 1 4 2948 4 7 13 9 14146 8 13 10 2 16784 3 2 6 5 30337 1 6 7 8 14239 2 6 11 5 13749 12 1 10 5 30827 4 6 11 8 18780 9 10 8 5 6336 7 9 1 3 3101 10 3 4 13 56678 7 6 3 8 8258 11 7 12 6 19046 13 6 9 8 46356 9 5 11 13 56570 9 1 10 5 6193 8 6 9 11 16854 3 7 4 9 53573 8 12 10 1 28135 10 3 8 4 31411 11 1 3 12 34534 8 6 4 13 3527 1 6 10 9 52307 11 7 1 12 2886 12 11 1 6 17659 13 5 6 8 48834 11 2 1 10 52951 3 9 13 7 21054 1 5 11 9 14507 11 5 12 4 42040 1 6 12 7 46414 5 12 3 10 26239 6 10 7 8 40762 8 11 6 10 38538 13 1 10 7 31140 9 10 13 4 34164 13 6 7 12 49696 6 13 3 5 36003 8 9 13 6 58409 3 10 7 9 20693 2 1 11 12 22653 5 8 4 7 49888 5 3 2 11 29911 8 12 6 9 30964 8 3 13 6 23597 4 1 6 7 31657 4 6 8 7 13 33639 13 8 10 3 27863 5 2 1 12 1408 4 11 1 12 59010 63 10 11 9 8 23611 10 8 6 11 12410 4 6 7 9 44390 8 4 1 6 16543 1 2 8 10 37452 11 12 6 13 28968 11 12 2 8 59617 1 9 11 2 28631 11 6 5 1 27251 2 7 10 4 42503 7 8 10 3 13673 9 13 11 7 30308 6 1 12 9 4888 13 1 9 8 19475 8 7 3 5 34187 8 1 12 3 46266 6 10 12 5 32855 3 7 13 1 38427 2 5 13 3 59487 6 11 1 13 2098 1 4 13 6 22239 13 7 12 3 28703 12 3 7 4 32 9 8 2 13 35271 10 13 6 12 36422 12 6 9 8 44303 1 9 13 11 22962 11 13 6 12 39518 5 6 13 11 47909 4 13 1 8 10654 11 8 12 4 31956 7 12 9 13 35923 4 9 3 2 34736 13 2 10 1 22945 7 10 8 13 36947 1 4 12 13 19432 7 12 13 4 48718 9 5 13 11 18827 11 2 1 12 45444 8 12 6 13 33175 4 2 11 13 56186 2 9 3 11 33218 12 13 8 1 50727 13 1 8 2 48138 7 1 5 3 1926 6 4 10 1 40997 11 3 1 4 26033 6 10 13 1 40988 11 12 5 4 25199 4 3 1 10 23498 3 6 12 7 24306 13 10 12 3 53255 3 13 4 12 14517 7 10 9 3 29925 9 11 12 13 28333 3 5 13 6 13602 13 12 9 6 10394 8 4 12 6 57471 9 3 4 7 34723 11 9 5 3 38480 12 9 10 11 48048 4 3 6 7 31884 2 10 4 5 57654 86 1 6 5 13 56577 6 8 2 5 20429 11 13 9 3 2243 3 1 10 12 55231 9 5 7 8 29964 5 11 8 1 29624 6 9 3 1 43055 12 13 10 8 52132 10 8 4 1 5729 7 3 6 8 53097 11 12 7 1 18711 12 7 6 13 44397 10 12 5 7 53574 5 3 4 13 27078 11 2 5 10 43623 3 7 1 8 57350 10 12 4 9 19752 5 13 9 3 59380 4 7 13 6 32575 7 5 6 11 13593 13 7 12 6 38282 13 7 6 2 45430 6 2 5 10 38082 2 11 13 7 53557 10 6 7 13 40461 6 11 7 1 22007 4 7 2 3 22386 9 7 11 10 35337 2 6 11 7 4129 6 13 5 3 31813 1 11 6 9 11749 5 11 8 13 21858 5 12 9 11 2470 13 10 6 11 14503 8 4 1 3 10783 1 10 12 7 47116 11 1 8 10 25034 8 1 4 9 23350 3 10 1 9 56717 13 2 8 12 5825 12 3 13 7 35628 10 6 1 12 26901 2 13 3 5 2775 1 8 9 7 1294 7 13 12 2 48170 11 9 13 1 34311 9 6 3 13 30663 8 3 10 6 5853 1 10 2 4 19880 9 2 3 12 48990 3 7 11 4 51558 8 13 2 4 9698 9 4 5 1 6834 3 4 12 2 20941 11 3 9 7 40108 13 11 2 4 2594 8 9 10 13 12242 1 8 10 5 42413 7 1 11 3 17779 1 5 8 3 6934 4 9 8 11 10235 8 11 10 2 18879 11 4 8 2 12691 9 7 5 2 44947 3 2 5 4 30042 2 7 12 4 27185 6 5 10 1 28695 12 9 1 5 53813 8 12 9 3 24719 6 1 4 11 22716 1 13 10 8 39981 12 11 5 2 22412 6 11 2 4 14457 4 11 5 3 39658 10 11 2 1 33056 1 3 6 9 16958 6 11 12 7 50779 8 10 6 13 24824 7 10 1 13 35692 13 4 8 9 32885 7 6 4 3 10948 4 5 7 1 36875 5 10 6 7 58746 10 7 8 12 39453 8 4 12 1 46674 11 3 1 8 48103 0

    Read the article

  • Many to Many with LINQ-To-Sql and ASP.NET MVC

    - by Jonathan Stowell
    Hi All, I will restrict this to the three tables I am trying to work with Problem, Communications, and ProbComms. The scenario is that a Student may have many Problems concurrently which may affect their studies. Lecturers may have future communications with a student after an initial problem is logged, however as a Student may have multiple Problems the Lecturer may decide that the discussion they had is related to more than one Problem. Here is a screenshot of the LINQ-To-Sql representation of my DB: LINQ-To-Sql Screenshot At the moment in my StudentController I have a StudentFormViewModel Class: // //ViewModel Class public class StudentFormViewModel { IProbCommRepository probCommRepository; // Properties public Student Student { get; private set; } public IEnumerable<ProbComm> ProbComm { get; private set; } // // Dependency Injection enabled constructors public StudentFormViewModel(Student student, IEnumerable<ProbComm> probComm) : this(new ProbCommRepository()) { this.Student = student; this.ProbComm = probComm; } public StudentFormViewModel(IProbCommRepository pRepository) { probCommRepository = pRepository; } } When I go to the Students Detail Page this runs: public ActionResult Details(string id) { StudentFormViewModel viewdata = new StudentFormViewModel(studentRepository.GetStudent(id), probCommRepository.FindAllProblemComms(id)); if (viewdata == null) return View("NotFound"); else return View(viewdata); } The GetStudent works fine and returns an instance of the student to output on the page, below the student I output all problems logged against them, but underneath these problems I want to show the communications related to the Problem. The LINQ I am using for ProbComms is This is located in the Model class ProbCommRepository, and accessed via a IProbCommRepository interface: public IQueryable<ProbComm> FindAllProblemComms(string studentEmail) { return (from p in db.ProbComms where p.Problem.StudentEmail.Equals(studentEmail) orderby p.Problem.ProblemDateTime select p); } However for example if I have this data in the ProbComms table: ProblemID CommunicationID 1 1 1 2 The query returns two rows so I assume I somehow have to groupby Problem or ProblemID but I am not too sure how to do this with the way I have built things as the return type has to be ProbComm for the query as thats what Model class its located in. When it comes to the view the Details.aspx calls two partial views each passing the relevant view data through, StudentDetails works fine page: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<MitigatingCircumstances.Controllers.StudentFormViewModel>" %> <% Html.RenderPartial("StudentDetails", this.ViewData.Model.Student); %> <% Html.RenderPartial("StudentProblems", this.ViewData.Model.ProbComm); %> StudentProblems uses a foreach loop to loop through records in the Model and I am trying another foreach loop to output the communication details: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<IEnumerable<MitigatingCircumstances.Models.ProbComm>>" %> <script type="text/javascript" language="javascript"> $(document).ready(function() { $("DIV.ContainerPanel > DIV.collapsePanelHeader > DIV.ArrowExpand").toggle( function() { $(this).parent().next("div.Content").show("slow"); $(this).attr("class", "ArrowClose"); }, function() { $(this).parent().next("div.Content").hide("slow"); $(this).attr("class", "ArrowExpand"); }); }); </script> <div class="studentProblems"> <% var i = 0; foreach (var item in Model) { %> <div id="ContainerPanel<%= i = i + 1 %>" class="ContainerPanel"> <div id="header<%= i = i + 1 %>" class="collapsePanelHeader"> <div id="dvHeaderText<%= i = i + 1 %>" class="HeaderContent"><%= Html.Encode(String.Format("{0:dd/MM/yyyy}", item.Problem.ProblemDateTime))%></div> <div id="dvArrow<%= i = i + 1 %>" class="ArrowExpand"></div> </div> <div id="dvContent<%= i = i + 1 %>" class="Content" style="display: none"> <p> Type: <%= Html.Encode(item.Problem.CommunicationType.TypeName) %> </p> <p> Problem Outline: <%= Html.Encode(item.Problem.ProblemOutline)%> </p> <p> Mitigating Circumstance Form: <%= Html.Encode(item.Problem.MCF)%> </p> <p> Mitigating Circumstance Level: <%= Html.Encode(item.Problem.MitigatingCircumstanceLevel.MCLevel)%> </p> <p> Absent From: <%= Html.Encode(String.Format("{0:g}", item.Problem.AbsentFrom))%> </p> <p> Absent Until: <%= Html.Encode(String.Format("{0:g}", item.Problem.AbsentUntil))%> </p> <p> Requested Follow Up: <%= Html.Encode(String.Format("{0:g}", item.Problem.RequestedFollowUp))%> </p> <p>Problem Communications</p> <% foreach (var comm in Model) { %> <p> <% if (item.Problem.ProblemID == comm.ProblemID) { %> <%= Html.Encode(comm.ProblemCommunication.CommunicationOutline)%> <% } %> </p> <% } %> </div> </div> <br /> <% } %> </div> The issue is that using the example data before the Model has two records for the same problem as there are two communications for that problem, therefore duplicating the output. Any help with this would be gratefully appreciated. Thanks, Jon

    Read the article

< Previous Page | 250 251 252 253 254 255 256 257 258 259 260 261  | Next Page >