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  • Scalable Database Tagging Schema

    - by Longpoke
    EDIT: To people building tagging systems. Don't read this. It is not what you are looking for. I asked this when I wasn't aware that RDBMS all have their own optimization methods, just use a simple many to many scheme. I have a posting system that has millions of posts. Each post can have an infinite number of tags associated with it. Users can create tags which have notes, date created, owner, etc. A tag is almost like a post itself, because people can post notes about the tag. Each tag association has an owner and date, so we can see who added the tag and when. My question is how can I implement this? It has to be fast searching posts by tag, or tags by post. Also, users can add tags to posts by typing the name into a field, kind of like the google search bar, it has to fill in the rest of the tag name for you. I have 3 solutions at the moment, but not sure which is the best, or if there is a better way. Note that I'm not showing the layout of notes since it will be trivial once I get a proper solution for tags. Method 1. Linked list tagId in post points to a linked list in tag_assoc, the application must traverse the list until flink=0 post: id, content, ownerId, date, tagId, notesId tag_assoc: id, tagId, ownerId, flink tag: id, name, notesId Method 2. Denormalization tags is simply a VARCHAR or TEXT field containing a tab delimited array of tagId:ownerId. It cannot be a fixed size. post: id, content, ownerId, date, tags, notesId tag: id, name, notesId Method 3. Toxi (from: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html, also same thing here: http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging) post: id, content, ownerId, date, notesId tag_assoc: ownerId, tagId, postId tag: id, name, notesId Method 3 raises the question, how fast will it be to iterate through every single row in tag_assoc? Methods 1 and 2 should be fast for returning tags by post, but for posts by tag, another lookup table must be made. The last thing I have to worry about is optimizing searching tags by name, I have not worked that out yet. I made an ASCII diagram here: http://pastebin.com/f1c4e0e53

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  • List of checkboxes

    - by Andrea Girardi
    Hi all, Happy New Year to all. I'm a newbie in VB.NET and ASP.NET. This is my problem: I retrieve a list of records from DB and, for every row, I need to show 4 checkboxes. I can use a checkboxlist for every rows, but it's not so clear how I can process the results after the submit. I've some object and some operations available for that object. From database I extract a list of object with all operations. For every operation I want to show a check box to enable or disable the operation. The result is something like that: OBJ1 - url - [] [x] [] OBJ2 - url - [] [x] [x] On url I've an href to another page created using the Id retrieved from DB. To create that I used this code: <td class="column-filename"> <strong> <asp:Label runat="server" Text='<%#DataBinder.Eval(Container.DataItem, "GroupName")%>'></asp:Label> </strong> </td> <td align="left"> <span style="vertical-align:middle"> <asp:CheckBoxList runat="server" ID="operations" RepeatDirection="Horizontal" RepeatLayout="Table"> <asp:ListItem Text="View"></asp:ListItem> <asp:ListItem Text="Upload"></asp:ListItem> <asp:ListItem Text="Move"></asp:ListItem> <asp:ListItem Text="Delete"></asp:ListItem> <asp:ListItem Text="Rename"></asp:ListItem> <asp:ListItem Text="Replace"></asp:ListItem> </asp:CheckBoxList> </span> </td> </asp> </asp> my problem is: how can I parse all checkboxes? could you help me or send me a link or any other resources to solve my issue? many thanks! Andrea

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  • please help me to find out where i am doing mistake in this code? i wnat retieve the value that i am

    - by user309381
    function reload(form) { var val = $('seltab').getValue(); new Ajax.Request('Website.php?cat=' +escape(val), { method:'get', onSuccess: function(transport){ var response = transport.responseText ; $("MyDivDB").innerHTML = transport.responseText ; alert("Success! \n\n" + response); }, onFailure: function(){ alert('Something went wrong...') } }); } </script> </head> title author pages $con = mysql_connect($dbhostname,$dbuserid,$dbpassword); if(!$con) { die ("connection failed".mysql_error()); } $db = mysql_select_db($dbname,$con); if(!$db) { die("Database is not selected".mysql_error()); } $query ="SELECT * FROM books NATURAL JOIN authors" ; $result = mysql_query($query); if(!$query) { die("Database is not query".mysql_error()); } while($row = mysql_fetch_array($result,MYSQL_ASSOC)) { $title = $row["title"]; $author = $row["author"]; $page = $row["pages"]; echo "<tr>"; echo "<td>$title</td>"; echo "<td>$author</td>"; echo "<td>$page</td>"; echo "</tr>"; } print "</table>"; echo "<select id = seltab onchange = 'reload(this.form)'>"; $querysel = "SELECT title_id,author FROM authors NATURAL JOIN books"; $result1 = mysql_query($querysel) ; while($rowID = mysql_fetch_assoc($result1)) { $TitleID = $rowID['title_id']; $author = $rowID['author']; print "<option value = $author>$author\n"; print "</option>"; } print "</select>"; ? Wbsite.php

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  • How to perform add/update of a model object that contains EntitySet

    - by David Liddle
    I have a similar concept to the SO questions/tags scenario however am trying to decide the best way of implementation. Tables Questions, QuestionTags and Tags Questions QuestionTags Tags --------- ------------ ---- QID QID TID QName TID TName When adding/updating a question I have 2 textboxes. The important part is a single textbox that allows users to enter in multiple Tags separated by spaces. I am using Linq2Sql so the Questions model has an EntitySet of QuestionTags with then link to Tags. My question is regarding the adding/updating of Questions (part 1), and also how to best show QuestionTags for a Question (part 2). Part 1 Before performing an add/update, my service layer needs to deal with 3 scenarios before passing to their respective repositories. Insert Tags that do not already exist Insert/Update Question Insert QuestionTags - when updating need to remove existing QuestionTags Here is my code below however started to get into a bit of a muddle. I've created extension methods on my repositories to get Tags WithNames etc. public void Add(Question q, string tags) { var tagList = tags.Split(new string[] { " " }, StringSplitOptions.RemoveEmptyEntries).ToList(); using (DB.TransactionScope ts = new DB.TransactionScope()) { var existingTags = TagsRepository.Get() .WithName(tagList) .ToList(); var newTags = (from t in tagList select new Tag { TName = t }).Except(existingTags, new TagsComparer()).ToList(); TagsRepository.Add(newTags); //need to insert QuestionTags QuestionsRepository.Add(q); ts.Complete(); } } Part 2 My second question is, when displaying a list of Questions how is it best to show their QuestionTags? For example, I have an Index view that shows a list of Questions in a table. One of the columns shows an image and when the user hovers over it shows the list of Tags. My current implementation is to create a custom ViewModel and show a List of QuestionIndexViewModel in the View. QuestionIndexViewModel { Question Question { get; set; } string Tags { get; set; } } However, this seems a bit clumsy and quite a few DB calls. public ViewResult Index() { var model= new List<QuestionIndexViewModel>(); //make a call to get a list of questions //foreach question make a call to get their QuestionTags, //to be able to get their Tag names and then join them //to form a single string. return View(model); } Also, just for test purposes using SQL Profiler, I decided to iterate through the QuestionTags entity set of a Question in my ViewModel however nothing was picked up in Profiler? What would be the reason for this?

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  • Setting up a "to-many" relationship value dependency for a transient Core Data attribute

    - by Greg Combs
    I've got a relatively complicated Core Data relationship structure and I'm trying to figure out how to set up value dependencies (or observations) across various to-many relationships. Let me start out with some basic info. I've got a classroom with students, assignments, and grades (students X assignments). For simplicity's sake, we don't really have to focus much on the assignments yet. StudentObj <--->> ScoreObj <<---> AssignmentObj Each ScoreObj has a to-one relation with the StudentObj and the AssignmentObj. ScoreObj has real attributes for the numerical grade, the turnInDate, and notes. AssignmentObj.scores is the set of Score objects for that assignment (N = all students). AssignmentObj has real attributes for name, dueDate, curveFunction, gradeWeight, and maxPoints. StudentObj.scores is the set of Score objects for that student (N = all assignments). StudentObj also has real attributes like name, studentID, email, etc. StudentObj has a transient (calculated, not stored) attribute called gradeTotal. This last item, gradeTotal, is the real pickle. it calculates the student's overall semester grade using the scores (ScoreObj) from all their assignments, their associated assignment gradeWeights, curves, and maxPoints, and various other things. This gradeTotal value is displayed in a table column, along with all the students and their individual assignment grades. Determining the value of gradeTotal is a relatively expensive operation, particularly with a large class, therefore I want to run it only when necessary. For simplicity's sake, I'm not storing that gradeTotal value in the core data model. I don't mind caching it somewhere, but I'm having a bitch of a time determining where and how to best update that cache. I need to run that calculation for each student whenever any value changes that affects their gradeTotal. If this were a simple to-one relationship, I know I could use something like keyPathsForValuesAffectingGradeTotal ... but it's more like a many-to-one-to-many relationship. Does anyone know of an elegant (and KVC correct) solution? I guess I could tear through all those score and assignment objects and tell them to register their students as observers. But this seems like a blunt force approach.

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  • How to add new object to an IList mapped as a one-to-many with NHibernate?

    - by Jørn Schou-Rode
    My model contains a class Section which has an ordered list of Statics that are part of this section. Leaving all the other properties out, the implementation of the model looks like this: public class Section { public virtual int Id { get; private set; } public virtual IList<Static> Statics { get; private set; } } public class Static { public virtual int Id { get; private set; } } In the database, the relationship is implemented as a one-to-many, where the table Static has a foreign key pointing to Section and an integer column Position to store its index position in the list it is part of. The mapping is done in Fluent NHibernate like this: public SectionMap() { Id(x => x.Id); HasMany(x => x.Statics).Cascade.All().LazyLoad() .AsList(x => x.WithColumn("Position")); } public StaticMap() { Id(x => x.Id); References(x => x.Section); } Now I am able to load existing Statics, and I am also able to update the details of those. However, I cannot seem to find a way to add new Statics to a Section, and have this change persisted to the database. I have tried several combinations of: mySection.Statics.Add(myStatic) session.Update(mySection) session.Save(myStatic) but the closest I have gotten (using the first two statements), is to an SQL exception reading: "Cannot insert the value NULL into column 'Position'". Clearly an INSERT is attempted here, but NHibernate does not seem to automatically append the index position to the SQL statement. What am I doing wrong? Am I missing something in my mappings? Do I need to expose the Position column as a property and assign a value to it myself? EDIT: Apparently everything works as expected, if I remove the NOT NULL constraint on the Static.Position column in the database. I guess NHibernate makes the insert and immediatly after updates the row with a Position value. While this is an anwers to the question, I am not sure if it is the best one. I would prefer the Position column to be not nullable, so I still hope there is some way to make NHibernate provide a value for that column directly in the INSERT statement. Thus, the question is still open. Any other solutions?

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  • how can i use a javascript in gridview row

    - by cagin
    hi there, I want to use a flash chart in a gridview. you can see my codes in below: DataTable tbl = new DataTable(); tbl.Columns.Add("chart"); DataRow rw; rw = tbl.NewRow(); rw["chart"] = @"<div id=""chart5Div""></div> <script type=""text/javascript""> var chart = new FusionCharts(""Charts/FCF_MSLine.swf"", ""ChId1"", ""500"", ""300""); var strXml = ""<graph numdivlines='4' lineThickness='3' showValues='0' numVDivLines='10' formatNumberScale='1' rotateNames='1' decimalPrecision='1' anchorRadius='2' anchorBgAlpha='0' numberPrefix='$' divLineAlpha='30' showAlternateHGridColor='1' yAxisMinValue='800000' shadowAlpha='50' >""; strXml += ""<categories >""; strXml += ""<category Name='Jan' />""; strXml += ""<category Name='Feb' />""; strXml += ""<category Name='Mar' />""; strXml += ""<category Name='Apr' />""; strXml += ""</categories >""; strXml += ""<dataset seriesName='Current Year' color='A66EDD' anchorBorderColor='A66EDD' anchorRadius='4'>""; strXml += ""<set value='1127654' />""; strXml += ""<set value='1226234' />""; strXml += ""<set value='1299456' />""; strXml += ""<set value='1311565' />""; strXml += ""</dataset>""; strXml += ""</graph>""; chart.setDataXML(strXml); chart.render(""chart5Div""); </script>"; tbl.Rows.Add(rw); GridView1.DataSource = tbl; GridView1.DataBind(); I must create dynamicly my datasource. But i can see just string value instead of my chart in gridview when page running. But chart code is running correctly between table tags. How can i use these codes in gridview?? KR

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  • how to refactor user-permission system?

    - by John
    Sorry for lengthy question. I can't tell if this should be a programming question or a project management question. Any advice will help. I inherited a reasonably large web project (1 year old) from a solo freelancer who architected it then abandoned it. The project was a mess, but I cleaned up what I could, and now the system is more maintainable. I need suggestions on how to extend the user-permission system. As it is now, the database has a t_user table with the column t_user.membership_type. Currently, there are 4 membership types with the following properties: 3 of the membership types are almost functionally the same, except for the different monthly fees each must pay 1 of the membership type is a "fake-user" type which has limited access ( different business logic also applies) With regards to the fake-user type, if you look in the system's business logic files, you will see a lot of hard-coded IF statements that do something like if (fake-user) { // do something } else { // a paid member of type 1,2 or 3 // proceed normally } My client asked me to add 3 more membership types to the system, each of them with unique features to be implemented this month, and substantive "to-be-determined" features next month. My first reaction is that I need to refactor the user-permission system. But it concerns me that I don't have enough information on the "to-be-determined" membership type features for next month. Refactoring the user-permission system will take a substantive amount of time. I don't want to refactor something and throw it out the following month. I get substantive feature requests on a monthly basis that come out of the blue. There is no project road map. I've asked my client to provide me with a roadmap of what they intend to do with the new membership types, but their answer is along the lines of "We just want to do [feature here] this month. We'll think of something new next month." So questions that come to mind are: 1) Is it dangerous for me to refactor the user permission system not knowing what membership type features exist beyond a month from now? 2) Should I refactor the user permission system regardless? Or just continue adding IF statements as needed in all my controller files? Or can you recommend a different approach to user permission systems? Maybe role-based ? 3) Should this project have a road map? For a 1 year old project like mine, how far into the future should this roadmap project? 4) Any general advice on the best way to add 3 new membership types?

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  • Help With LINQ: Mixed Joins and Specifying Default Values

    - by Corey O.
    I am trying to figure out how to do a mixed-join in LINQ with specific access to 2 LINQ objects. Here is an example of how the actual TSQL query might look: SELECT * FROM [User] AS [a] INNER JOIN [GroupUser] AS [b] ON [a].[UserID] = [b].[UserID] INNER JOIN [Group] AS [c] ON [b].[GroupID] = [c].[GroupID] LEFT JOIN [GroupEntries] AS [d] ON [a].[GroupID] = [d].[GroupID] WHERE [a].[UserID] = @UserID At the end, basically what I would like is an enumerable object full of GroupEntry objects. What am interested is the last two tables/objects in this query. I will be displaying Groups as a group header, and all of the Entries underneath their group heading. If there are no entries for a group, I still want to see that group as a header without any entries. Here's what I have so far: So from that I'd like to make a function: public void DisplayEntriesByUser(int user_id) { MyDataContext db = new MyDataContext(); IEnumberable<GroupEntries> entries = ( from user in db.Users where user.UserID == user_id join group_user in db.GroupUsers on user.UserID = group_user.UserID into a from join1 in a join group in db.Groups on join1.GroupID equals group.GroupID into b from join2 in b join entry in db.Entries.DefaultIfEmpty() on join2.GroupID equals entry.GroupID select entry ); Group last_group_id = 0; foreach(GroupEntry entry in entries) { if (last_group_id == 0 || entry.GroupID != last_group_id) { last_group_id = entry.GroupID; System.Console.WriteLine("---{0}---", entry.Group.GroupName.ToString().ToUpper()); } if (entry.EntryID) { System.Console.WriteLine(" {0}: {1}", entry.Title, entry.Text); } } } The example above does not work quite as expected. There are 2 problems that I have not been able to solve: I still seem to be getting an INNER JOIN instead of a LEFT JOIN on the last join. I am not getting any empty results, so groups without entries do not appear. I need to figure out a way so that I can fill in the default values for blank sets of entries. That is, if there is a group without an entry, I would like to have a mostly blank entry returned, except that I'd want the EntryID to be null or 0, the GroupID to be that of of the empty group that it represents, and I'd need a handle on the entry.Group object (i.e. it's parent, empty Group object). Any help on this would be greatly appreciated. Note: Table names and real-world representation were derived purely for this example, but their relations simplify what I'm trying to do.

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  • Using JSON Data to Populate a Google Map with Database Objects

    - by MikeH
    I'm revising this question after reading the resources mentioned in the original answers and working through implementing it. I'm using the google maps api to integrate a map into my Rails site. I have a markets model with the following columns: ID, name, address, lat, lng. On my markets/index view, I want to populate a map with all the markets in my markets table. I'm trying to output @markets as json data, and that's where I'm running into problems. I have the basic map displaying, but right now it's just a blank map. I'm following the tutorials very closely, but I can't get the markers to generate dynamically from the json. Any help is much appreciated! Here's my setup: Markets Controller: def index @markets = Market.filter_city(params[:filter]) respond_to do |format| format.html # index.html.erb format.json { render :json => @market} format.xml { render :xml => @market } end end Markets/index view: <head> <script type="text/javascript" src="http://www.google.com/jsapi?key=GOOGLE KEY REDACTED, BUT IT'S THERE" > </script> <script type="text/javascript"> var markets = <%= @markets.to_json %>; </script> <script type="text/javascript" charset="utf-8"> google.load("maps", "2.x"); google.load("jquery", "1.3.2"); </script> </head> <body> <div id="map" style="width:400px; height:300px;"></div> </body> Public/javascripts/application.js: function initialize() { if (GBrowserIsCompatible() && typeof markets != 'undefined') { var map = new GMap2(document.getElementById("map")); map.setCenter(new GLatLng(40.7371, -73.9903), 13); map.addControl(new GLargeMapControl()); function createMarker(latlng, market) { var marker = new GMarker(latlng); var html="<strong>"+market.name+"</strong><br />"+market.address; GEvent.addListener(marker,"click", function() { map.openInfoWindowHtml(latlng, html); }); return marker; } var bounds = new GLatLngBounds; for (var i = 0; i < markets.length; i++) { var latlng=new GLatLng(markets[i].lat,markets[i].lng) bounds.extend(latlng); map.addOverlay(createMarker(latlng, markets[i])); } } } window.onload=initialize; window.onunload=GUnload;

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  • Strange compilation error - GAS3 generated class

    - by subh
    I am pretty new to GraniteDS..So far I have been able to successfully configure it to work with my remote java services as well as generate the equivalent AS3 files from my POJO's. But I am getting this strange error while building one of the classes using GAS3 [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[77,29] Syntax error: expecting identifier before use. public function set use(value:String):void { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[77,52] Syntax error: expecting leftparen before leftbrace. public function set use(value:String):void { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[77,52] Syntax error: expecting identifier before leftbrace. public function set use(value:String):void { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[77,52] Syntax error: expecting rightparen before leftbrace. public function set use(value:String):void { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[80,29] Syntax error: expecting identifier before use. public function get use():String { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[80,42] Syntax error: expecting leftparen before leftbrace. public function get use():String { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[80,42] Syntax error: expecting identifier before leftbrace. public function get use():String { [ERROR] C:\TestGDS_All\TestGDS-flex-remoteobjects\target\generated-sources\com\mycompany\TestGDS\masterdata\model\TankGradesMlBas e.as:[80,42] Syntax error: expecting rightparen before leftbrace. public function get use():String { The java class appears like this @Entity` @Table(name = "mmd_tank_grades_ml") @SuppressWarnings("serial") public class TankGradesMl implements Serializable { .... private String use; @Basic @Column(name = "USE", length = 45) public String getUse() { return use; } public void setUse(String use) { this.use = use; } What am I doing wrong? How to resolve this error? I tried by changing the java source variable like below private String usedFor; ---- @Basic @Column(name = "USE", length = 45) public String getUsedFor() { return usedFor; } /** * @param use * new value for use */ public void setUsedFor(String usedFor) { this.usedFor = usedFor; } and the error is gone...not sure why it was throwing exception for 'use'..too small for variable name :-)

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  • Memory allocation and release for UIImage in iPhone?

    - by rkbang
    Hello all, I am using following code in iPhone to get smaller cropped image as follows: - (UIImage*) getSmallImage:(UIImage*) img { CGSize size = img.size; CGFloat ratio = 0; if (size.width < size.height) { ratio = 36 / size.width; } else { ratio = 36 / size.height; } CGRect rect = CGRectMake(0.0, 0.0, ratio * size.width, ratio * size.height); UIGraphicsBeginImageContext(rect.size); [img drawInRect:rect]; UIImage *tempImg = [UIGraphicsGetImageFromCurrentImageContext() retain]; UIGraphicsEndImageContext(); return [tempImg autorelease]; } - (UIImage*)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect { //create a context to do our clipping in UIGraphicsBeginImageContext(rect.size); CGContextRef currentContext = UIGraphicsGetCurrentContext(); //create a rect with the size we want to crop the image to //the X and Y here are zero so we start at the beginning of our //newly created context CGFloat X = (imageToCrop.size.width - rect.size.width)/2; CGFloat Y = (imageToCrop.size.height - rect.size.height)/2; CGRect clippedRect = CGRectMake(X, Y, rect.size.width, rect.size.height); //CGContextClipToRect( currentContext, clippedRect); //create a rect equivalent to the full size of the image //offset the rect by the X and Y we want to start the crop //from in order to cut off anything before them CGRect drawRect = CGRectMake(0, 0, imageToCrop.size.width, imageToCrop.size.height); CGContextTranslateCTM(currentContext, 0.0, drawRect.size.height); CGContextScaleCTM(currentContext, 1.0, -1.0); //draw the image to our clipped context using our offset rect //CGContextDrawImage(currentContext, drawRect, imageToCrop.CGImage); CGImageRef tmp = CGImageCreateWithImageInRect(imageToCrop.CGImage, clippedRect); //pull the image from our cropped context UIImage *cropped = [UIImage imageWithCGImage:tmp];//UIGraphicsGetImageFromCurrentImageContext(); CGImageRelease(tmp); //pop the context to get back to the default UIGraphicsEndImageContext(); //Note: this is autoreleased*/ return cropped; } I am using following line of code in cellForRowAtIndexPath to update the image of the cell: cell.img.image = [self imageByCropping:[self getSmallImage:[UIImage imageNamed:@"goal_image.png"]] toRect:CGRectMake(0, 0, 36, 36)]; Now when I add this table view and pop it from navigation controller, I see a memory hike.I see no leaks but memory keeps climbing. Please note that the images changes for each row and I am creating the controller using lazy initialization that is I create or alloc it whenever I need it. I saw on internet many people facing the same issue, but very rare good solutions. I have multiple views using the same way and I see almost memory raised to 4MB within 20-25 view transitions. What is the good solution to resolve this issue. tnx.

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  • Can i have One form tag inside Another in ASP.net MVC RC2

    - by coolguy97
    Hi all, I am currently Developing application in MVC2 I have want to used mutiple form tags in My application In My View I have Created a table which has Delete option which i am doing through Post for Individual Delete so i have Create form tag for each button. i also want user to give option to delete mutiple records so i am providing them with checkboxes.This form should have all the values of checkboxes and all. so form gets render Like this for Each delete button <form action="/Home/MutipleDelete" method="post"> <input class="button " name="Compare" type="submit" value="Mutipledelete" style="margin-right:132px;" /> <input id="chk1" name="chk1" type="checkbox" value="true" /> <form action="/Home/Delete" method="post"> <input type="submit" class="submitLink" value="member1" /> <input type="hidden" name="hfmem1" id="hfmem1" value="1" /> </form> <input id="chk2" name="chk2" type="checkbox" value="true" /> <form action="/Home/Delete" method="post"> <input type="submit" class="submitLink" value="member2" /> <input type="hidden" name="hfmem2" id="hfmem2" value="2" /> </form> </form> The following is not working . but IF i write my code that form renders in this way <form action="/Home/MutipleDelete" method="post"> <input class="button " name="Compare" type="submit" value="Mutipledelete" style="margin-right:132px;" /> </form> <input id="chk1" name="chk1" type="checkbox" value="true" /> <form action="/Home/Delete" method="post"> <input type="submit" class="submitLink" value="member1" /> <input type="hidden" name="hfmem1" id="hfmem1" value="1" /> </form> <input id="chk2" name="chk2" type="checkbox" value="true" /> <form action="/Home/Delete" method="post"> <input type="submit" class="submitLink" value="member2" /> <input type="hidden" name="hfmem2" id="hfmem2" value="2" /> </form> it is working in Mozilla but not in IE.I have debug and Checked values in formcollection In contoller.What to do.?

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  • which way is correct to retrive data from oracle??

    - by rima
    before answer me plz thinking about the futures of these kind of program and answer me plz. I wanna get some data from oracle server like: 1-get all the function,package,procedure and etc for showing them or drop them & etc... 2-compile my *.sql files,get the result if they have problem & etc... becuz I was beginner in oracle first of all I for solve the second problem I try to connect to sqlPlus by RUN sqlplus and trace the output(I mean,I change the output stream of shell and trace what happend and handle the assigned message to customer. NOW THIS PART SUCCEED. just a little bit I have problem with get all result because the output is asynchronous.any way... [in this case I log in to oracle Server by send argument to the sqlplus by make a process in c#] after that I try to get all function,package or procedure name,but I have problem in speed!so I try to use oracle.DataAccess.dll to connect the database. now I m so confusing about: which way is correct way to build a program that work like Oracle Developer! I do not have any experience for like these program how work. If Your answer is I must use the second way follow this part plz: I search a little bit the Golden,PLedit (Benthic software),I have little bit problem how I must create the connection string?because I thinking about how I can find the host name or port number that oracle work on them?? am I need read the TNSNames.Ora file? IF your answer is I must use the first way follow this part plz: do u have any Idea for how I parse the output?because for example the result of a table is so confusing...[i can handle & program it but I really need someone experience,because the important things to me learn how such software work so nice and with quick response?] All of the has different style in output... If you are not sure Can u help me which book can help me in this way i become expert? becuz for example all the C# write just about how u can connect to DB and the DB books write how u can use this DB program,I looking for a book that give me some Idea how develop an interface for do transaction between these two.not simple send and receive data,for example how write a compiler for them. the language of book is not different for me i know C#,java,VB,sql,Oracle Thanks.

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  • deallocated memory in tableview: message sent to deallocated instance

    - by Kirn
    I tried looking up other issues but couldn't find anything to match so here goes: I'm trying to display text in the table view so I use this bit of code: // StockData is an object I created and it pulls information from Yahoo APIs based on // a stock ticker stored in NSString *heading NSArray* tickerValues = [heading componentsSeparatedByString:@" "]; StockData *chosenStock = [[StockData alloc] initWithContents:[tickerValues objectAtIndex:0]]; [chosenStock getData]; // Set up the cell... NSDictionary *tempDict = [chosenStock values]; NSArray *tempArr = [tempDict allValues]; cell.textLabel.text = [tempArr objectAtIndex:indexPath.row]; return cell; This is all under cellForRowAtIndexPath When I try to release the chosenStock object though I get this error: [CFDictionary release]: message sent to deallocated instance 0x434d3d0 Ive tried using NSZombieEnabled and Build and Analyze to detect problems but no luck thus far. Ive even gone so far as to comment bits and pieces of the code with NSLog but no luck. I'll post the code for StockData below this. As far as I can figure something is getting deallocated before I do the release but I'm not sure how. The only place I've got release in my code is under dealloc method call. Here's the StockData code: // StockData contains all stock information pulled in through Yahoo! to be displayed @implementation StockData @synthesize ticker, values; - (id) initWithContents: (NSString *)newName { if(self = [super init]){ ticker = newName; } return self; } - (void) getData { NSURL *url = [NSURL URLWithString: [NSString stringWithFormat:@"http://download.finance.yahoo.com/d/quotes.csv?s=%@&f=%@&e=.csv", ticker, @"chgvj1"]]; NSError *error; NSURLResponse *response; NSURLRequest *request = [NSURLRequest requestWithURL:url]; NSData *stockData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error]; if(stockData) { NSString *tempStr = [[NSString alloc] initWithData:stockData encoding:NSASCIIStringEncoding]; NSArray *receivedValuesArr = [tempStr componentsSeparatedByString:@","]; [tempStr release]; values = [NSDictionary dictionaryWithObjects:receivedValuesArr forKeys:[@"change, high, low, volume, market" componentsSeparatedByString:@", "]]; } else { NSLog(@"Connection failed: %@", error); } } - (void)dealloc { [ticker release]; [values release]; [super dealloc]; NSLog(@"Release took place fine"); } @end

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  • UITableViewCell separator line disappears on scroll

    - by iconso
    I'm trying to have a separator cell with a custom image. I did try something like that: In my cellForRowAtIndexPath: NSString *cellIdentifier = [NSString stringWithFormat:@"identifier"]; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellIdentifier]; } cell.textLabel.font = [UIFont fontWithName:@"Helvetica" size:19]; cell.textLabel.text = [self.menuItems objectAtIndex:indexPath.row]; cell.textLabel.textColor = [UIColor colorWithRed:128/255.0f green:129/255.0f blue:132/255.0f alpha:1.0f]; cell.backgroundColor = [UIColor whiteColor]; UIImageView *imagView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"reaL.png"]]; imagView.frame = CGRectMake(0, cellHeight, cellWidth, 1); [cell.contentView addSubview:imagView]; switch (indexPath.row) { case 0: cell.imageView.image = [self imageWithImage:[UIImage imageNamed:@"img1.png"] scaledToSize:CGSizeMake(27, 27)]; cell.imageView.highlightedImage = [self imageWithImage:[UIImage imageNamed:@"route.png"] scaledToSize:CGSizeMake(27, 27)]; break; case 1: cell.imageView.image = [self imageWithImage:[UIImage imageNamed:@"img.png"] scaledToSize:CGSizeMake(27, 27)]; cell.imageView.highlightedImage = [self imageWithImage:[UIImage imageNamed:@"money.png"] scaledToSize:CGSizeMake(27, 27)]; break; case 2: cell.imageView.image = [self imageWithImage:[UIImage imageNamed:@"auto.png"] scaledToSize:CGSizeMake(27, 27)]; cell.imageView.highlightedImage = [self imageWithImage:[UIImage imageNamed:@"cars.png"] scaledToSize:CGSizeMake(27, 27)]; break; case 3: cell.imageView.image = [self imageWithImage:[UIImage imageNamed:@"impostazioni.png"] scaledToSize:CGSizeMake(27, 27)]; cell.imageView.highlightedImage = [self imageWithImage:[UIImage imageNamed:@"impostazioni.png"] scaledToSize:CGSizeMake(27, 27)]; // cell.imageView.contentMode = UIViewContentModeScaleAspectFill; break; case 4: cell.imageView.image = [self imageWithImage:[UIImage imageNamed:@"info.png"] scaledToSize:CGSizeMake(27, 27)]; cell.imageView.highlightedImage = [self imageWithImage:[UIImage imageNamed:@"info.png"] scaledToSize:CGSizeMake(27, 27)]; break; default: break; } return cell; When I lunch the app everything is good, but when I scroll the the table, or when I select a cell the separator lines disappear. How I can have a permanent custom line separator?

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  • Javascript self contained sandbox events and client side stack

    - by amnon
    I'm in the process of moving a JSF heavy web application to a REST and mainly JS module application . I've watched "scalable javascript application architecture" by Nicholas Zakas on yui theater (excellent video) and implemented much of the talk with good success but i have some questions : I found the lecture a little confusing in regards to the relationship between modules and sandboxes , on one had to my understanding modules should not be effected by something happening outside of their sandbox and this is why they publish events via the sandbox (and not via the core as they do access the core for hiding base libary) but each module in the application gets a new sandbox ? , shouldn't the sandbox limit events to the modoules using it ? or should events be published cross page ? e.g. : if i have two editable tables but i want to contain each one in a different sandbox and it's events effect only the modules inside that sandbox something like messabe box per table which is a different module/widget how can i do that with sandbox per module , ofcourse i can prefix the events with the moduleid but that creates coupling that i want to avoid ... and i don't want to package modules toghter as one module per combination as i already have 6-7 modules ? while i can hide the base library for small things like id selector etc.. i would still like to use the base library for module dependencies and resource loading and use something like yui loader or dojo.require so in fact i'm hiding the base library but the modules themself are defined and loaded by the base library ... seems a little strange to me libraries don't return simple js objects but usualy wrap them e.g. : u can do something like $$('.classname').each(.. which cleans the code alot , it makes no sense to wrap the base and then in the module create a dependency for the base library by executing .each but not using those features makes a lot of code written which can be left out ... and implemnting that functionality is very bug prone does anyonen have any experience with building a front side stack of this order ? how easy is it to change a base library and/or have modules from different libraries , using yui datatable but doing form validation with dojo ... ? some what of a combination of 2+4 if u choose to do something like i said and load dojo form validation widgets for inputs via yui loader would that mean dojocore is a module and the form module is dependant on it ? Thanks .

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  • Rails, Edit page update in a window

    - by Mike
    I have my code working so that I have a table of businesses. There's a pencil icon you can click on the edit the business information. The edit information comes up in a partial inside of a modal pop up box. The only problem is that once they make the changes they want and click update, it sends them to the 'show' page for that business. What I want to happen is have the pop up box close and have it update the information. This is my update function in my controller. def update @business = Business.find(params[:id]) respond_to do |format| if @business.update_attributes(params[:business]) flash[:notice] = 'Business was successfully updated.' format.html { redirect_to(business_url(@business)) } format.js else format.html { render :action => "edit" } format.xml { render :xml => @business.errors, :status => :unprocessable_entity } end end end I tried following railscast 43 and i created an .rjs file but I couldn't get that to work at all. My update was still taking me to the show page. Any help would be appreciated. EDIT: Added some more code. <% form_for(@business) do |f| %> <%= f.error_messages %> <p> <%= f.label :name %><br /> <%= f.text_field :name %> </p> ... <%= f.label :business_category %><br /> <%= f.select :business_category_id, @business_categories_map, :selected => @business.business_category_id %> </p> <p> <%= f.label :description %><br /> <%= f.text_area :description %> </p> <p> <%= f.submit 'Update' %> </p> <% end %> This is my form inside of my edit page which is being called through the index in a pop up by: <div id="popupEdit<%=h business.id %>" class="popupContact"> <a class="popupClose<%=h business.id %>" id="popupClose">x</a> <% if business.business_category_id %> <% @business = business %> <%= render "business/edit" %> <% end %> </div>

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  • How do I find the Next Closest Date to today from a list of dates in a Plist on iOS?

    - by user1173823
    Situation: In short, I have a football schedule. I would like to use a custom cell which provides more info for only the next game date in the schedule. Issue: How do I find only the next closest game in the schedule (for iOS)? I've watched the WWDC 2013 video for "Solutions to Common Date and Time Issues" however this primarily applies to the Mac. I've searched numerous posts here and some are close but not what I need to find ONLY the next date from my list of dates in the schedule. From other posts I see where I can compare two specific dates, but this is not what I want to do. I want to find the next closest date that is equal to or after today from a list of dates. This is where I am now. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { //Populate the table from the plist NSDictionary *season = _schedContentArray[indexPath.section]; NSArray *schedule = season[@"Schedule"]; NSDictionary *game = schedule[indexPath.row]; //find the closest game date after today's date ?? NSString *gameDateStr = game[@"GameDate"]; NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar]; NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; dateFormatter.calendar=calendar; [dateFormatter setDateFormat:@"MM/dd/yy"]; NSDate *today = [NSDate date]; NSDate *gameDate = [dateFormatter dateFromString:gameDateStr]; //NSString *nextGame = NSLog(@"game date is %@",gameDate); The NSLog returns the game dates (except for the open date): 2013-11-11 16:10:05.979 Clemson Football[24060:70b] game date is 2013-08-31 04:00:00 +0000 2013-11-11 16:10:05.982 Clemson Football[24060:70b] game date is 2013-09-07 04:00:00 +0000 2013-11-11 16:10:05.985 Clemson Football[24060:70b] game date is (null) 2013-11-11 16:10:05.987 Clemson Football[24060:70b] game date is 2013-09-19 04:00:00 +0000 2013-11-11 16:10:05.988 Clemson Football[24060:70b] game date is 2013-09-28 04:00:00 +0000 2013-11-11 16:10:05.990 Clemson Football[24060:70b] game date is 2013-10-05 04:00:00 +0000 2013-11-11 16:10:05.992 Clemson Football[24060:70b] game date is 2013-10-12 04:00:00 +0000 2013-11-11 16:10:05.993 Clemson Football[24060:70b] game date is 2013-10-19 04:00:00 +0000 2013-11-11 16:10:05.995 Clemson Football[24060:70b] game date is 2013-10-26 04:00:00 +0000 2013-11-11 16:10:05.996 Clemson Football[24060:70b] game date is 2013-11-02 04:00:00 +0000 2013-11-11 16:10:05.998 Clemson Football[24060:70b] game date is 2013-11-09 05:00:00 +0000 2013-11-11 16:10:06.000 Clemson Football[24060:70b] game date is 2013-11-14 05:00:00 +0000 2013-11-11 16:10:06.001 Clemson Football[24060:70b] game date is 2013-11-23 05:00:00 +0000 2013-11-11 16:10:06.003 Clemson Football[24060:70b] game date is 2013-11-30 05:00:00 +0000 2013-11-11 16:10:06.005 Clemson Football[24060:70b] game date is 2013-12-07 05:00:00 +0000 Thanks in advance for any assistance you can provide. This seems like it should be simple but has been fairly frustrating. Let me know if you need additional info.

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  • SQL Native Client 10 Performance miserable (due to server-side cursors)

    - by namezero
    we have an application that uses ODBC via CDatabase/CRecordset in MFC (VS2010). We have two backends implemented. MSSQL and MySQL. Now, when we use MSSQL (with the Native Client 10.0), retrieving records with SELECT is dramatically slow via slow links (VPN, for example). The MySQL ODBC driver does not exhibit this nasty behavior. For example: CRecordset r(&m_db); r.Open(CRecordset::snapshot, L"SELECT a.something, b.sthelse FROM TableA AS a LEFT JOIN TableB AS b ON a.ID=b.Ref"); r.MoveFirst(); while(!r.IsEOF()) { // Retrieve CString strData; crs.GetFieldValue(L"a.something", strData); crs.MoveNext(); } Now, with the MySQL driver, everything runs as it should. The query is returned, and everything is lightning fast. However, with the MSSQL Native Client, things slow down, because on every MoveNext(), the driver communicates with the server. I think it is due to server-side cursors, but I didn't find a way to disable them. I have tried using: ::SQLSetConnectAttr(m_db.m_hdbc, SQL_ATTR_ODBC_CURSORS, SQL_CUR_USE_ODBC, SQL_IS_INTEGER); But this didn't help either. There are still long-running exec's to sp_cursorfetch() et al in SQL Profiler. I have also tried a small reference project with SQLAPI and bulk fetch, but that hangs in FetchNext() for a long time, too (even if there is only one record in the resultset). This however only happens on queries with LEFT JOINS, table-valued functions, etc. Note that the query doesn't take that long - executing the same SQL via SQL Studio over the same connection returns in a reasonable time. Question1: Is is possible to somehow get the native client to "cache" all results locally use local cursors in a similar fashion as the MySQL driver seems to do it? Maybe this is the wrong approach altogether, but I'm not sure how else to do this. All we want is to retrieve all data at once from a SELECT, then never talk the server again until the next query. We don't care about recordset updates, deletes, etc or any of that nonsense. We only want to retrieve data. We take that recordset, get all the data, and delete it. Question2: Is there a more efficient way to just retrieve data in MFC with ODBC?

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  • Linq query challenge - can this be done?

    - by vdh_ant
    My table structure is as follows: Person 1-M PesonAddress Person 1-M PesonPhone Person 1-M PesonEmail Person 1-M Contract Contract M-M Program Contract M-1 Organization At the end of this query I need a populated object graph where each person has their: PesonAddress's PesonPhone's PesonEmail's PesonPhone's Contract's - and this has its respective Program's Now I had the following query and I thought that it was working great, but it has a couple of problems: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") where people.Contract.Any( contract => (param.OrganizationId == contract.OrganizationId) && contract.Program.Any( contractProgram => (param.ProgramId == contractProgram.ProgramId))) select people; The problem is that it filters the person to the criteria but not the Contracts or the Contract's Programs. It brings back all Contracts that each person has not just the ones that have an OrganizationId of x and the same goes for each of those Contract's Programs respectively. What I want is only the people that have at least one contract with an OrgId of x with and where that contract has a Program with the Id of y... and for the object graph that is returned to have only the contracts that match and programs within that contract that match. I kinda understand why its not working, but I don't know how to change it so it is working... This is my attempt thus far: from people in ctx.People.Include("PersonAddress") .Include("PersonLandline") .Include("PersonMobile") .Include("PersonEmail") .Include("Contract") .Include("Contract.Program") let currentContracts = from contract in people.Contract where (param.OrganizationId == contract.OrganizationId) select contract let currentContractPrograms = from contractProgram in currentContracts let temp = from x in contractProgram.Program where (param.ProgramId == contractProgram.ProgramId) select x where temp.Any() select temp where currentContracts.Any() && currentContractPrograms.Any() select new Person { PersonId = people.PersonId, FirstName = people.FirstName, ..., ...., MiddleName = people.MiddleName, Surname = people.Surname, ..., ...., Gender = people.Gender, DateOfBirth = people.DateOfBirth, ..., ...., Contract = currentContracts, ... }; //This doesn't work But this has several problems (where the Person type is an EF object): I am left to do the mapping by myself, which in this case there is quite a lot to map When ever I try to map a list to a property (i.e. Scholarship = currentScholarships) it says I can't because IEnumerable is trying to be cast to EntityCollection Include doesn't work Hence how do I get this to work. Keeping in mind that I am trying to do this as a compiled query so I think that means anonymous types are out.

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  • Can't Show image in gridview using templates

    - by n10i
    i am trying to load images from the northwind database (categories table, images that are stored in the database) into grid view control. But it dosenot seems to work. Plz! have a look... Default.aspx <asp:GridView ID="GridView1" runat="server" AllowSorting="True" AutoGenerateColumns="False" DataKeyNames="CategoryID" DataSourceID="NorthWindSQLExpressConnectionString" EnableModelValidation="True"> <Columns> <asp:BoundField DataField="CategoryID" HeaderText="CategoryID" InsertVisible="False" ReadOnly="True" SortExpression="CategoryID" /> <asp:BoundField DataField="CategoryName" HeaderText="CategoryName" SortExpression="CategoryName" /> <asp:BoundField DataField="Description" HeaderText="Description" SortExpression="Description" /> <asp:TemplateField HeaderText="Picture" SortExpression="Picture"> <EditItemTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("Picture") %>'></asp:TextBox> </EditItemTemplate> <ItemTemplate> <asp:Image ID="Image1" runat="server" ImageUrl='<%# RetriveImage(Eval("CategoryID")) %>' /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> <asp:SqlDataSource ID="NorthWindSQLExpressConnectionString" runat="server" ConnectionString="<%$ ConnectionStrings:NorthwindSQLExpressConnectionString %>" SelectCommand="SELECT [CategoryID], [CategoryName], [Description], [Picture] FROM [Categories]"> </asp:SqlDataSource> </div> </form> [Partial] Default.aspx.cs protected string RetriveImage(object eval) { return ("ImageHandler.ashx?CategoryID=" + eval.ToString()); } [Partial] ImageHandler.ashx public void ProcessRequest(HttpContext context) { if (context.Request.QueryString == null) { } else { try { using (var sqlCon = new SqlConnection(conString)) { const string cmdString = "Select picture from Categories where CategoryID=@CategoryID"; using (var sqlCmd = new SqlCommand(cmdString, sqlCon)) { sqlCmd.Parameters.AddWithValue("@CategoryID", context.Request.QueryString["CategoryID"]); string trmp = sqlCmd.ToString(); sqlCon.Open(); using (var sqlDr = sqlCmd.ExecuteReader()) { sqlDr.Read(); context.Response.BinaryWrite((byte[])sqlDr["Picture"]); } } } } catch (Exception ex) { context.Response.Write(ex.Message); } } }

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  • Assign value to HTML textbox from JSP

    - by prakash_d22
    Hello I am creating a web page to add some information about given product.I need to enter id,name,description and image as information.I need the id to be auto generated.I am using jsp and database as access.I am fetching the count(*)+1 value from database and assigning to my html text box but its showing as null.can i get some help? Code: <body> <%@page import="java.sql.*"%> <%! String no; %> <% try{ Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); Connection con = DriverManager.getConnection("jdbc:odbc:pd"); ResultSet rs = null; Statement st = con.createStatement(); String sql = ("select count(*)+1 from products"); st.executeUpdate(sql); while (rs.next()) { no=rs.getString("count(*)+1"); } rs.close(); st.close(); con.close(); } catch(Exception e){} %> <Form name='Form1' action="productcode.jsp" method="post"> <table width="1024" border="0"> <tr> <td width="10">&nbsp;</td> <td width="126">Add Product: </td> <td width="277">&nbsp;</td> <td width="583">&nbsp;</td> </tr> <tr> <td>&nbsp;</td> <td>Product Id:</td> <td><label> <input type="text" name="id" value="<%= no%>"/> </label></td> <td>&nbsp;</td> .... and so on

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  • Which MS technologies would be suited for a data intensive application?

    - by steve.tse
    I'm a junior VB.net developer with little application design knowledge. I've been reading a lot of material online regarding different design patterns, frameworks, and methodologies. It's become a bit confusing for me. Right now I'm trying to decide on what language would be best suited to convert an existing VB6 application (with SQL server backend.) I need to update the UI and add more user functionality and reporting capabilities. Initially I was thinking of using WPF and attempting the MVVM model for this big project. Reports would be generated from SSRS. A peer suggested using ASP.net and I don't have enough experience to determine what would be better. The senior programmers here are stuck on using VB6 and don't have any input on what to use. They are encouraging me to use the latest technologies. This application would be for ~20 users in a central location. Ideally I would stick to a Microsoft .net language. Current interface is similar to a datagrid table where the user would click in to see the detail of each record. They would need to have multiple records open at any given time. I look forward to all the advice I can get. EDIT 2010/04/22 2:47 PM EST What is your audience? Internal clients within an intranet How complex are the interactions you expect to implement? not very... displaying data from SQL server to UI. Allow user updates to said data. Typically just one user modifying a record. Do you require near real-time data updates? no How often do you expect to update the application after the first release? twice/year Do you expect a well-defined set of client platforms? Yes, windows xp environment, potentially upgrading to Win7. Currently in IE.6 moving to IE7 or 8 within a couple of months. Do users need access from anywhere? No, just from their PC.

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  • MySQL - Calculating fields on the fly vs storing calculated data

    - by Christian Varga
    Hi Everyone, I apologise if this has been asked before, but I can't seem to find an answer to a question that I have about calculating on the fly vs storing fields in a database. I read a few articles that suggested it was preferable to calculate when you can, but I would just like to know if that still applies to the following 2 examples. Example 1. Say you are storing data relating to a car. You store the fuel tank size in litres, and how many litres it uses per 100km. You also want to know how many KMs it can travel, which can be calculated from the tank size and economy. I see 2 ways of doing this: When a car is added or updated, calculate the amount of KMs and store this as a static field in the database. Every time a car is accessed, calculate the amount of KMs on the fly. Because the cars economy/tank size doesn't change (although it could be edited), the KMs is a pretty static value. I don't see why we would calculate it every single time the car is accessed. Wouldn't this waste cpu time as opposed to simply storing it in a separate field in the database and calculating only when a car is added or updated? My next example, which is almost an entirely different question (but on the same topic), relates to counting children. Let's say we have a app which has categories and items. We have a view where we display all the categories, and a count of all the items inside each category. Again, I'm wondering what's better. To perform a MySQL query to count all the items in each category every single time the page is accessed? Or store the count in a field in the categories table and update when an item is added / deleted? I know it is redundant to store anything that can be calculated, but I worry that calculating fields or counting records might be slow as opposed to storing the data in a field. If it's not then please let me know, I just want to learn about when to use either method. On a small scale I guess it wouldn't matter either way, but apps like Facebook, would they really count the amount of friends you have every time someone views your profile or would they just store it as a field? I'd appreciate any responses to both of these scenarios, and any resource that might explain the benefits of calculating vs storing. Thanks in advance, Christian

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