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  • UITableView which has sections as alphabets and various rows within each section

    - by lifemoves
    Hello I have a database in which I am inserting data by parsing an XML document. Populating the data using Navigation bar control view. I have various NSObjects defined in a class and have populated the data using NSMutableArray. Using UITableview I have populated the data. My question is : I have populated the data with the sections defined in it as alphabets so I have total of 26 sections. Each section has data in form of name. Now when I use cellforrowatIndexpath it does not give me the correct index for row and section together. My code is : (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } /* Index names as in AB ....Z */ NSString *strIndexNames = [arrCharacters objectAtIndex:indexPath.section]; /* object sections has names in each section */ NSArray *arrIndexedCategories = [objSections objectForKey:strIndexNames]; NSString *strName = [arrIndexedCategories objectAtIndex:indexPath.row] ; cell.textLabel.text = strName; cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator; cell.textLabel.font = [UIFont systemFontOfSize:16]; return cell; } Any help whatsoever will be really helpful. S

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  • Selecting two specific mysql table rows in a single query

    - by Scotta
    Lets say I have a table with 20 entries. They are sorted by date (date is a column name _) in descending order. How would I go about selecting ONLY the newest entry and the 15th oldest entry? I am getting all 15 results by doing the following query SELECT * FROM mytable m WHERE col1 = "zzz" ORDER BY date DESC LIMIT 15;

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  • How to return result set based on other rows

    - by understack
    I've 2 tables - packages and items. Items table contains all items belonging to the packages along with location information. Like this: Packages table id, name, type(enum{general,special}) 1, name1, general 2, name2, special Items table id, package_id, location 1, 1, America 2, 1, Africa 3, 1, Europe 4, 2, Europe Question: I want to find all 'special' packages belonging to a location and if no special package is found then it should return 'general' packages belonging to same location. So, for 'Europe' : package 2 should be returned since it is special package (Though package 1 also belongs to Europe but not required since its a general package) for 'America' : package 1 should be returned since there are no special packages

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  • Remove all rows in duplication (different from distinct row selection)

    - by user1671401
    How can I remove EVERY duplicating row in a DataTable, based on the value of two columns that are in duplication. Unfortunately, I am unable to find the equivalent LINQ Query. (I dont want distinct values even). The table below shall explain my problem I want to delete every row in duplication based on Column_A and Column_B COLUMN_A      COLUMN_B      COLUMN_C     COLUMN_D..... A                       B C                       D E                       F G                       H A                       B E                       F EXPECTED OUTPUT: COLUMN_A      COLUMN_B      COLUMN_C     COLUMN_D..... C                       D G                       H Please help

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  • Updating multiple rows with an array

    - by Copephobia
    I have a table that holds user information. One of the columns holds the position of the user in the game they are in. When a game is being created, I need to update the positions of the users of each team. Here is an example: Game id : 7 Team 1 users : 1,2 Team 2 users : 3,4 team1_position : array(1,2) team2_position : array(13,14) What I want to do is update the user table using the array of positions in the SET area. My goal is to be able to update the users without the need for their id (I have different size game boards, so I have multiple position arrays for each board size) How can I do something like this: UPDATE user SET position='(team1_position)' WHERE game = '7' AND team = '1' I feel like it would be a waste of resources to select all the id's of each team and update them separately.

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  • Concatenate and group multiple rows in Oracle

    - by user1693347
    Suppose I have a table like this: NAME GROUP name1 groupA name2 groupB name5 groupC name4 groupA name3 groupC I'd like to have a result like this: GROUP NAMES groupA name1,name4 groupB name2 groupC name3,name5 If there were only one column in the table, I could concatenate the records by doing the following, but with grouping in the context, I really don't have much idea. Any suggestion is welcome, thanks in advance! Concatatenating one column table: SELECT names FROM (SELECT SYS_CONNECT_BY_PATH(names,' ') names, level FROM name_table START WITH names = (SELECT names FROM name_table WHERE rownum = 1) CONNECT BY PRIOR names < names ORDER BY level DESC) WHERE rownum = 1

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  • CONCAT_WS rows in JOIN

    - by Alex Kiselev
    i have tables profiles (id, name, deleted) categories (id, name, deleted) profiles_categories (id, profile_id, category_id, , deleted) I have wrong query SELECT p.id, p.name CONCAT_WS(', ', c.name) AS keywords_categories FROM profiles p LEFT JOIN profiles_categories pc ON p.id = pc.profile_id LEFT JOIN categories c ON pc.id = c.id WHERE p.deleted = FALSE So, i want have result with all profiles with concan categories.name. Thanks

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  • MySQL: Select remaining rows

    - by Bjork24
    I've searched everywhere for this, but I can't seem to find a solution. Perhaps I'm using the wrong terms. Either way, I'm turning to good ol' trusty S.O. to help my find the answer. I have two tables, we'll call them 'tools' and 'installs' tools = id, name, version installs = id, tool_id, user_id The 'tools' table records available tools, which are then installed by a user and recorded in the 'installs' table. Selecting the installed tools are simple enough: SELECT tools.name FROM tools LEFT JOIN installs ON tools.id = installs.tool_id WHERE user_id = 99 ; How do I select the remaining tools -- the ones that have yet to be installed by user #99? I'm sorry if this is painfully obvious, but I just can't seem to figure it out! Thanks for the help!

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  • mysql select when matching multiple rows

    - by user1735943
    I have a project where I need to select only the users that answered to some questions in a certain way (based on a filter). The filter table (filter) looks like this question | answer Q1 | A Q2 | B The user table (answers) looks like this user | question | answer 1 | Q1 | A 1 | Q2 | D 2 | Q1 | A 2 | Q2 | B How can I select from the user table only the user(s) that match the filter? I tried "SELECT user FROM answers WHERE (question = Q1 AND answer = A) AND (question = Q2 AND answer = B)" and it doesn't work -- I get an empty result. Thank you.

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  • 3 column layout with css display table, with first row having multiple rows?

    - by Damainman
    I am working on a new website which: Has 3 columns - Each Column being a cell First column has 3 rows (Logo, Nav, icons) - Has a Div with display: table which wraps arround 3 divs with display:table-row. Other two columns only have 1 row. With the middle column being the content area. However since this is my first time using display:table, I am running into some things that aren't so clear to me. I was trying to avoid floating divs. If I need multiple rows with one cell in each row per column, do I embed each cell in a row or just create each row and not declare cells. I understand that browsers automatically create the missing elements but I want to make sure I do this properly to avoid any side effects that might occur due to the browser automatically creating the missing elements. Edit: I think my brain is just over worked, I guess I can accomplish this by just using 3 divs in the first column instead of using a nested table div with the rows. This just popped into my head.

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  • MVC HTML.RenderAction – Error: Duration must be a positive number

    - by BarDev
    On my website I want the user to have the ability to login/logout from any page. When the user select login button a modal dialog will be present to the user for him to enter in his credentials. Since login will be on every page, I thought I would create a partial view for the login and add it to the layout page. But when I did this I got the following error: Exception Details: System.InvalidOperationException: Duration must be a positive number. There are other ways to work around this that would not using partial views, but I believe this should work. So to test this, I decided to make everything simple with the following code: Created a layout page with the following code @{Html.RenderAction("_Login", "Account");} In the AccountController: public ActionResult _Login() { return PartialView("_Login"); } Partial View _Login <a id="signin">Login</a> But when I run this simple version this I still get this error: Exception Details: System.InvalidOperationException: Duration must be a positive number. Source of error points to "@{Html.RenderAction("_Login", "Account");}" There are some conversations on the web that are similar to my problem, which identifies this as bug with MVC (see links below). But the links pertain to Caching, and I'm not doing any caching. OuputCache Cache Profile does not work for child actions http://aspnet.codeplex.com/workitem/7923 Asp.Net MVC 3 Partial Page Output Caching Not Honoring Config Settings Asp.Net MVC 3 Partial Page Output Caching Not Honoring Config Settings Caching ChildActions using cache profiles won't work? Caching ChildActions using cache profiles won't work? I'm not sure if this makes a difference, but I'll go ahead and add it here. I'm using MVC 3 with Razor. Update Stack Trace [InvalidOperationException: Duration must be a positive number.] System.Web.Mvc.OutputCacheAttribute.ValidateChildActionConfiguration() +624394 System.Web.Mvc.OutputCacheAttribute.OnActionExecuting(ActionExecutingContext filterContext) +127 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func1 continuation) +72 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func1 continuation) +784922 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList1 filters, ActionDescriptor actionDescriptor, IDictionary2 parameters) +314 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +784976 System.Web.Mvc.Controller.ExecuteCore() +159 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +335 System.Web.Mvc.<c_DisplayClassb.b_5() +62 System.Web.Mvc.Async.<c_DisplayClass1.b_0() +20 System.Web.Mvc.<c_DisplayClasse.b_d() +54 System.Web.Mvc.<c_DisplayClass4.b_3() +15 System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Func`1 func) +41 System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +1363 [HttpException (0x80004005): Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'.] System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +2419 System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +275 System.Web.HttpServerUtilityWrapper.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +94 System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) +838 System.Web.Mvc.Html.ChildActionExtensions.RenderAction(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues) +56 ASP._Page_Views_Shared_SiteLayout_cshtml.Execute() in c:\Projects\Odat Projects\Odat\Source\Presentation\Odat.PublicWebSite\Views\Shared\SiteLayout.cshtml:80 System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +280 System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +104 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +173 System.Web.WebPages.WebPageBase.Write(HelperResult result) +89 System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action1 body) +234 System.Web.WebPages.WebPageBase.PopContext() +234 System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +384 System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() +33 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func1 continuation) +784900 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func1 continuation) +784900 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) +265 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +784976 System.Web.Mvc.Controller.ExecuteCore() +159 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +335 System.Web.Mvc.<c_DisplayClassb.b_5() +62 System.Web.Mvc.Async.<c_DisplayClass1.b_0() +20 System.Web.Mvc.<c_DisplayClasse.b_d() +54 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +453 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371 Update When I Break in Code, it errors at @{Html.RenderAction("_Login", "Account");} with the following exception. The inner exception Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'. at System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) at System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) at System.Web.HttpServerUtilityWrapper.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) at System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) at System.Web.Mvc.Html.ChildActionExtensions.RenderAction(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues) at ASP._Page_Views_Shared_SiteLayout_cshtml.Execute() in c:\Projects\Odat Projects\Odat\Source\Presentation\Odat.PublicWebSite\Views\Shared\SiteLayout.cshtml:line 80 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.WebPages.WebPageBase.Write(HelperResult result) at System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action1 body) at System.Web.WebPages.WebPageBase.PopContext() at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func1 continuation) Answer Thanks Darin Dimitrov Come to find out, my AccountController had the following attribute [System.Web.Mvc.OutputCache(NoStore =true, Duration = 0, VaryByParam = "*")]. I don't believe this should caused a problem, but when I removed the attribute everything worked. BarDev

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  • Ruby number_to_currency displays a totally wrong number!

    - by SueP
    Greetings! I’m an old Delphi programmer making the leap to the Mac, Ruby, Rails, and web programming in general. I’m signed up for the Advanced Rails workshop at the end of the month. In the meantime, I’ve been working on porting a mission-critical (of course) app from Delphi to RAILS. It feels like I’ve spent most of the past year with my head buried in a book or podcast. Right now, I’ve hit a major issue and I’m tearing my hair out. I literally don’t know where to go with this, I desperately don’t want to deploy with this bug, and I’m feeling a bit frantic. (The company database is currently running on an ancient XP box that’s looking rustier by the day.) So, I set up a test database that shows the problem. I’m running: OS/X 10.6.3 Rails 2.3.5 ruby 1.8.7 (2009-06-08 patchlevel 173) [universal-darwin10.0] MySQL 5.1.38-log via socket MySQL Client Version 5.1.8 ActiveRecord::Schema.define(:version => 20100406222528) do create_table “money”, :force => true do |t| t.decimal “amount_due”, :precision => 10, :scale => 2, :default => 0.0 t.decimal “balance”, :precision => 10, :scale => 2, :default => 0.0 t.text “memofield” t.datetime “created_at” t.datetime “updated_at” end The index view is right out of the generator, slightly modified to add the formatting that's breaking on me. Listing money <table> <tr> <th>Amount</th> <th>Amount to_s </th> <th>Balance to $</th> <th>Balance with_precision </th> <th>Memofield</th> </tr> <% @money.each do |money| %> <tr> <td><%=h money.amount_due %></td> <td><%=h money.amount_due.to_s(‘F’) %></td> <td><%=h number_to_currency(money.balance) %></td> <td><%=h number_with_precision(money.balance, :precision => 2) %></td> <td><%=h money.memofield %></td> <td><%= link_to ‘Show’, money %></td> <td><%= link_to ‘Edit’, edit_money_path(money) %></td> <td><%= link_to ‘Destroy’, money, :confirm => ‘Are you sure?’, :method => :delete %></td> </tr> *<% end %> *</table> <%= link_to ‘New money’, new_money_path %> This seemed to work pretty well. Then I started testing with production data and hit a major problem with number_to_currency. The number in the database is: 10542.28, I verified it with the MySQL Query Browser. RAILS will display this as 10542.28 unless I call number_to_currency, then that number is displayed as: $15422.80 The error seems to happen with any number between 10,000.00 and 10,999.99 So far, I haven’t seen it outside of that range, but I obviously haven’t tested everything. I guess my workaround is to remove number_to_currency, but that leaves the views looking really sloppy and unprofessional. The formatting is messed up, things don’t line up properly and I can’t force the display to 2 decimal places. I’m seriously hoping there is an easy fix for this. I can’t imagine this being a widespread problem. It would affect so many people that someone would have fixed it! But I don’t know where to go from here. I’d desperately like some help. (Later – number_with_precision fails the same way number_to_currency does.) Sue Petersen

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  • Performance considerations for common SQL queries

    - by Jim Giercyk
    Originally posted on: http://geekswithblogs.net/NibblesAndBits/archive/2013/10/16/performance-considerations-for-common-sql-queries.aspxSQL offers many different methods to produce the same results.  There is a never-ending debate between SQL developers as to the “best way” or the “most efficient way” to render a result set.  Sometimes these disputes even come to blows….well, I am a lover, not a fighter, so I decided to collect some data that will prove which way is the best and most efficient.  For the queries below, I downloaded the test database from SQLSkills:  http://www.sqlskills.com/sql-server-resources/sql-server-demos/.  There isn’t a lot of data, but enough to prove my point: dbo.member has 10,000 records, and dbo.payment has 15,554.  Our result set contains 6,706 records. The following queries produce an identical result set; the result set contains aggregate payment information for each member who has made more than 1 payment from the dbo.payment table and the first and last name of the member from the dbo.member table.   /*************/ /* Sub Query  */ /*************/ SELECT  a.[Member Number] ,         m.lastname ,         m.firstname ,         a.[Number Of Payments] ,         a.[Average Payment] ,         a.[Total Paid] FROM    ( SELECT    member_no 'Member Number' ,                     AVG(payment_amt) 'Average Payment' ,                     SUM(payment_amt) 'Total Paid' ,                     COUNT(Payment_No) 'Number Of Payments'           FROM      dbo.payment           GROUP BY  member_no           HAVING    COUNT(Payment_No) > 1         ) a         JOIN dbo.member m ON a.[Member Number] = m.member_no         /***************/ /* Cross Apply  */ /***************/ SELECT  ca.[Member Number] ,         m.lastname ,         m.firstname ,         ca.[Number Of Payments] ,         ca.[Average Payment] ,         ca.[Total Paid] FROM    dbo.member m         CROSS APPLY ( SELECT    member_no 'Member Number' ,                                 AVG(payment_amt) 'Average Payment' ,                                 SUM(payment_amt) 'Total Paid' ,                                 COUNT(Payment_No) 'Number Of Payments'                       FROM      dbo.payment                       WHERE     member_no = m.member_no                       GROUP BY  member_no                       HAVING    COUNT(Payment_No) > 1                     ) ca /********/                    /* CTEs  */ /********/ ; WITH    Payments           AS ( SELECT   member_no 'Member Number' ,                         AVG(payment_amt) 'Average Payment' ,                         SUM(payment_amt) 'Total Paid' ,                         COUNT(Payment_No) 'Number Of Payments'                FROM     dbo.payment                GROUP BY member_no                HAVING   COUNT(Payment_No) > 1              ),         MemberInfo           AS ( SELECT   p.[Member Number] ,                         m.lastname ,                         m.firstname ,                         p.[Number Of Payments] ,                         p.[Average Payment] ,                         p.[Total Paid]                FROM     dbo.member m                         JOIN Payments p ON m.member_no = p.[Member Number]              )     SELECT  *     FROM    MemberInfo /************************/ /* SELECT with Grouping   */ /************************/ SELECT  p.member_no 'Member Number' ,         m.lastname ,         m.firstname ,         COUNT(Payment_No) 'Number Of Payments' ,         AVG(payment_amt) 'Average Payment' ,         SUM(payment_amt) 'Total Paid' FROM    dbo.payment p         JOIN dbo.member m ON m.member_no = p.member_no GROUP BY p.member_no ,         m.lastname ,         m.firstname HAVING  COUNT(Payment_No) > 1   We can see what is going on in SQL’s brain by looking at the execution plan.  The Execution Plan will demonstrate which steps and in what order SQL executes those steps, and what percentage of batch time each query takes.  SO….if I execute all 4 of these queries in a single batch, I will get an idea of the relative time SQL takes to execute them, and how it renders the Execution Plan.  We can settle this once and for all.  Here is what SQL did with these queries:   Not only did the queries take the same amount of time to execute, SQL generated the same Execution Plan for each of them.  Everybody is right…..I guess we can all finally go to lunch together!  But wait a second, I may not be a fighter, but I AM an instigator.     Let’s see how a table variable stacks up.  Here is the code I executed: /********************/ /*  Table Variable  */ /********************/ DECLARE @AggregateTable TABLE     (       member_no INT ,       AveragePayment MONEY ,       TotalPaid MONEY ,       NumberOfPayments MONEY     ) INSERT  @AggregateTable         SELECT  member_no 'Member Number' ,                 AVG(payment_amt) 'Average Payment' ,                 SUM(payment_amt) 'Total Paid' ,                 COUNT(Payment_No) 'Number Of Payments'         FROM    dbo.payment         GROUP BY member_no         HAVING  COUNT(Payment_No) > 1   SELECT  at.member_no 'Member Number' ,         m.lastname ,         m.firstname ,         at.NumberOfPayments 'Number Of Payments' ,         at.AveragePayment 'Average Payment' ,         at.TotalPaid 'Total Paid' FROM    @AggregateTable at         JOIN dbo.member m ON m.member_no = at.member_no In the interest of keeping things in groupings of 4, I removed the last query from the previous batch and added the table variable query.  Here’s what I got:     Since we first insert into the table variable, then we read from it, the Execution Plan renders 2 steps.  BUT, the combination of the 2 steps is only 22% of the batch.  It is actually faster than the other methods even though it is treated as 2 separate queries in the Execution Plan.  The argument I often hear against Table Variables is that SQL only estimates 1 row for the table size in the Execution Plan.  While this is true, the estimate does not come in to play until you read from the table variable.  In this case, the table variable had 6,706 rows, but it still outperformed the other queries.  People argue that table variables should only be used for hash or lookup tables.  The fact is, you have control of what you put IN to the variable, so as long as you keep it within reason, these results suggest that a table variable is a viable alternative to sub-queries. If anyone does volume testing on this theory, I would be interested in the results.  My suspicion is that there is a breaking point where efficiency goes down the tubes immediately, and it would be interesting to see where the threshold is. Coding SQL is a matter of style.  If you’ve been around since they introduced DB2, you were probably taught a little differently than a recent computer science graduate.  If you have a company standard, I strongly recommend you follow it.    If you do not have a standard, generally speaking, there is no right or wrong answer when talking about the efficiency of these types of queries, and certainly no hard-and-fast rule.  Volume and infrastructure will dictate a lot when it comes to performance, so your results may vary in your environment.  Download the database and try it!

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  • Lost transparency in SDL surfaces drawn manually

    - by Christian Ivicevic
    I want to create SDL_Surface objects for each layer of my 2d tile-based map so that I have to render only one surface per layer rather than too many tiles. With normal tiles which do not have transparent areas this works well, however I am not able to create a SDL_Surface with transparent pixels everywhere to be able to draw some tiles on specific parts which should be visible (I do NOT want the whole surface to appear with a specific opacity - I want to create overlaying tiles where one can look through). Currently I am creating my layers like this to draw with SDL_BlitSurface on them: SDL_Surface* layer = SDL_CreateRGBSurface( SDL_HWSURFACE | SDL_SRCALPHA, layerWidth, layerHeight, 32, 0, 0, 0, 0); If you have a look at this screenshot I have provided here you can see that the bottom layer with no transparent parts gets rendered correctly. However the overlay with the tree tile (which is transparent in the top left corner) is drawn own its own surface which is black and not transparent as expected. The expected result (concerning the transparency) can be seen here Can anyone explain me how to handle surfaces which are actually transparent rather than drawing all my overlay tiles separately?

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  • How was collision detection handled in The Legend of Zelda: A Link to the Past?

    - by Restart
    I would like to know how the collision detection was done in The Legend of Zelda: A Link To The Past. The game is 16x16 tile based, so how did they do the tiles where only a quarter or half of the tile is occupied? Did they use a smaller grid for collision detection like 8x8 tiles, so four of them make one 16x16 tile of the texture grid? But then, they also have true half tiles which are diagonally cut and the corners of the tiles seem to be round or something. If Link walks into tiles corner he can keep on walking and automatically moves around it's corner. How is that done? I hope someone can help me out here.

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  • How was collision detection handled in The Legend of Zelda: A Link to the Past?

    - by Restart
    I would like to know how the collision detection was done in The Legend of Zelda: A Link To The Past. The game is 16x16 tile based, so how did they do the tiles where only a quarter or half of the tile is occupied? Did they use a smaller grid for collision detection like 8x8 tiles, so four of them make one 16x16 tile of the texture grid? But then, they also have true half tiles which are diagonally cut and the corners of the tiles seem to be round or something. If Link walks into tiles corner he can keep on walking and automatically moves around it's corner. How is that done? I hope someone can help me out here.

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  • Efficient way to calculate "vision cones" on 2D tile map?

    - by OverMachoGrande
    I'm trying to calculate which tiles a particular unit can "see" if facing a certain direction on a tile map (within a certain range and angle of facing). The easiest way would be to draw a certain number of tiles outward and raycast to each tile. However, I'm hoping for something slightly more efficient. A picture says a thousand words: The red dot is the unit (who's facing upwards). My goal is to calculate the yellow tiles. The green blocks are walls (walls are between tiles, and it's easy to check if you can pass between two tiles). The blue line represents something like the "raycasting" method I was talking about, but I'd rather not have to do this. EDIT: Units can only be facing north/south/east/west (0, 90, 180, or 270 degrees) and FoV is always 90 degrees. Should simplify some calculations. I'm thinking there's some sort of recursive-ish/stack-based/queue-based algorithm, but I can't quite figure it out. Thanks!

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  • Regular Expressions

    - by Rocky
    Hello Everyone, I am new to Stackoverflow and I have a quick question. Let's assume we are given a large number of HTML files (large as in theoretically infinite). How can I use Regular Expressions to extract the list of Phone Numbers from all those files? Explanation/expression will be really appreciated. The Phone numbers can be any of the following formats: (123) 456 7899 (123).456.7899 (123)-456-7899 123-456-7899 123 456 7899 1234567899 Thanks a lot for all your help and have a good one!

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  • Simple hardware RNG

    - by roygbiv
    I made a tongue-in-cheek comment to this question about making a hardware RNG. Does anyone know of any simple plans or can anyone descibe a simple hardware based RNG and the software to drive it? Go to Radio Shack. Buy a diode, an NTR resistor, a capacitor and serial cable. Cut off the end of the serial cable that does not fit on your computer. Solder the diode and resistor in series between pins DTR and DSR of the cable. Solder the capacitor between DSR and TXD pins. Write a small C program to do the following: Set DTR to 1. Start Timer. Monitor DSR until it goes to 1. Stop Timer. Calculate resistance from elapsed time. Retreive serveral bits from that value to use as part of random number. Repeat until enough bits have accumulated.

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  • Regular Expression for finding phone numbers

    - by Rocky
    Hello Everyone, I am new to Stackoverflow and I have a quick question. Let's assume we are given a large number of HTML files (large as in theoretically infinite). How can I use Regular Expressions to extract the list of Phone Numbers from all those files? Explanation/expression will be really appreciated. The Phone numbers can be any of the following formats: (123) 456 7899 (123).456.7899 (123)-456-7899 123-456-7899 123 456 7899 1234567899 Thanks a lot for all your help and have a good one!

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  • Generating random numbers in C

    - by moonstruckhorrors
    While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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  • Using the mpz_powm functions from the GMP/MPIR libraries with negative exponents

    - by Mihai Todor
    Please consider the following code: mpz_t x, n, out; mpz_init_set_ui(x, 2UL); mpz_init_set_ui(n, 7UL); mpz_init(out); mpz_invert(out, x, n); gmp_printf ("%Zd\n", out);//prints 4. 2 * 4 (mod 7) = 1. OK mpz_powm_ui(out, x, -1UL, n);//prints 1. 2 * 1 (mod 7) = 2. How come? gmp_printf ("%Zd\n", out); mpz_clear(x); mpz_clear(n); mpz_clear(out); I am unable to understand how the mpz_powm functions handle negative exponents, although, according to the documentation, it is supposed to support them. I would expect that raising a number to -1 modulo n is equivalent to inverting it modulo n. What am I missing here?

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  • Actionscript NetStream.play drops port in relative URLs

    - by Steve Middleton
    Hi, the current page my flash application is running from is http://localhost:3000/. I'm trying to play a video using NetStream.play(relativeURL) by using a relative URL (e.g. "myVideo.flv"), but when I look at the actual request made by actionscript, it's dropping the port number. (e.g. http://localhost/myVideo.flv). Is there something I can do on the flash side to make this work? Is anyone else having this problem?

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