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• Unit testing a 'legacy' WPF Application

  - by sc_ray

  The product I have been working on has been in development for the past six years. It started as a generic data entry portal into an insanely complex part WPF/part legacy application. The system has been developed for all these years without a single Unit test in its fold. Now, the point has been raised for a comprehensive unit testing framework. I have been recruited recently to work on this product and have been tasked to get the 'Testing' in order. Since the team that worked on the product for the last six years adopted 'Agile', the project lacks any documentation of the business rules or any design documents. I have been trying to write unit tests for some of the modules. But I am not sure what to Mock, how to setup my Test fixture and eventually what to Test for, since a casual glance of the methods does not reveal its intentions. Also, it has come to my attention that the code was not developed with a particular methodology in mind. Given the situation, I was wondering if the good people of Stackoverflow could provide me with some advise on how to salvage this situation. I have heard about the book 'Working with Legacy Code' that has something to say about this general situation but I was thinking about getting some pointers from individuals who have encountered similar situations within the technology stack(C#,VB,C++,.NET 3.5,WCF,SQL Server 2005).

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• SELECT SQL Variable - should i avoid using this syntax and always use SET?

  - by Sholom

  Hi All, This may look like a duplicate to here, but it's not. I am trying to get a best practice, not a technical answer (which i already (think) i know). New to SQL Server and trying to form good habits. I found a great explanation of the functional differences between SET @var = and SELECT @var = here: http://vyaskn.tripod.com/differences_between_set_and_select.htm To summarize what each has that the other hasn't (see source for examples): SET: ANSI and portable, recommended by Microsoft. SET @var = (SELECT column_name FROM table_name) fails when the select returns more then one value, eliminating the possibility of unpredictable results. SET @var = (SELECT column_name FROM table_name) will set @var to NULL if that's what SELECT column_name FROM table_name returned, thus never leaving @var at it's prior value. SELECT: Multiple variables can be set in one statement Can return multiple system variables set by the prior DML statement SELECT @var = column_name FROM table_name would set @var to (according to my testing) the last value returned by the select. This could be a feature or a bug. Behavior can be changed with SELECT @j = (SELECT column_name FROM table_name) syntax. Speed. Setting multiple variables with a single SELECT statement as opposed to multiple SET/SELECT statements is much quicker. He has a sample test to prove his point. If you could design a test to prove the otherwise, bring it on! So, what do i do? (Almost) always use SET @var =, using SELECT @var = is messy coding and not standard. OR Use SELECT @var = freely, it could accomplish more for me, unless the code is likely to be ported to another environment. Thanks

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• What's wrong with output parameters?

  - by Chris McCall

  Both in SQL and C#, I've never really liked output parameters. I never passed parameters ByRef in VB6, either. Something about counting on side effects to get something done just bothers me. I know they're a way around not being able to return multiple results from a function, but a rowset in SQL or a complex datatype in C# and VB work just as well, and seem more self-documenting to me. Is there something wrong with my thinking, or are there resources from authoritative sources that back me up? What's your personal take on this and why? What can I say to colleagues that want to design with output parameters that might convince them to use different structures? EDIT: interesting turn- the output parameter I was asking this question about was used in place of a return value. When the return value is "ERROR", the caller is supposed to handle it as an exception. I was doing that but not pleased with the idea. A coworker wasn't informed of the need to handle this condition and as a result, a great deal of money was lost as the procedure failed silently!

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• Codeigniter: how should I restructure db schema?

  - by Kevin Brown

  I don't even know if that's the right term. May it be known that I'm a major novice! I have three tables: users, profiles, and survey. Each one has user_id as it's first field, (auto-increment for users), and they're all tied by a foreign key constraint, CASCADE on DELETE. Currently, for each user, let's say user_id 1, they have a corresponding db entry in the other tables. For profiles it lists all their information, and the survey table holds all their survey information. Now I must change things...darn scope creep. Users need the ability to have multiple survey results. I imagine that this would be similar to a comment table for a blog... My entire app runs around the idea that a single user is linked to a constraining profile and survey. How should I structure my db? How should I design my app's db so that a user can have multiple tests/profiles for the test? Please assist! Any advice, information and personal-knowledge is appreciated! Right now the only way I know how to accompany my client is to create a pseudo-user for each test (so unnecessary) and list them in a view table (called "your tests")-- these are obtained from the db by saying: where user_id=manager_id

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• Security strategies for storing password on disk

  - by Mike

  I am building a suite of batch jobs that require regular access to a database, running on a Solaris 10 machine. Because of (unchangable) design constraints, we are required use a certain program to connect to it. Said interface requires us to pass a plain-text password over a command line to connect to the database. This is a terrible security practice, but we are stuck with it. I am trying to make sure things are properly secured on our end. Since the processing is automated (ie, we can't prompt for a password), and I can't store anything outside the disk, I need a strategy for storing our password securely. Here are some basic rules The system has multiple users. We can assume that our permissions are properly enforced (ie, if a file with a is chmod'd to 600, it won't be publically readable) I don't mind anyone with superuser access looking at our stored password Here is what i've got so far Store password in password.txt $chmod 600 password.txt Process reads from password.txt when it's needed Buffer overwritten with zeros when it's no longer needed Although I'm sure there is a better way.

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• How can flash call jquery function in its event

  - by user2955639

  I want jquery to do something during some of the events when an audio is playing. So I'm coding a function like this <script> $.fn.playMedia = function(options){ var opts = $.extend({}, { swfSrc: '' timeUpdated: function(currentTime){}, startPlay: function(){}, endPlay: function(){} }, options); return $(this).each(function(){ // call flash to play the media whose src is opts.swfSrc // Is it possible that flash can call the js functions(opts.timeUpdate, opts.startPlay and opts.endPlay) at each time of the event is triggered? }); }}; </script> // Usage <div id="player"></div> <script> $('#player').playMedia({ swfSrc: '/path/song.mp3', timeUpdated: function(currentTime){ comsole.log(currentTime); } }); </script> I'm a totally layman of flash, I just guess this works. Hope someone could tell me how to make up a swf file for this jquery function. Or is there any existing jquery plugin which does this thing but can re-design apperance flexibly. Thank you very much!

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• Convert a binary tree to linked list, breadth first, constant storage/destructive

  - by Merlyn Morgan-Graham

  This is not homework, and I don't need to answer it, but now I have become obsessed :) The problem is: Design an algorithm to destructively flatten a binary tree to a linked list, breadth-first. Okay, easy enough. Just build a queue, and do what you have to. That was the warm-up. Now, implement it with constant storage (recursion, if you can figure out an answer using it, is logarithmic storage, not constant). I found a solution to this problem on the Internet about a year back, but now I've forgotten it, and I want to know :) The trick, as far as I remember, involved using the tree to implement the queue, taking advantage of the destructive nature of the algorithm. When you are linking the list, you are also pushing an item into the queue. Each time I try to solve this, I lose nodes (such as each time I link the next node/add to the queue), I require extra storage, or I can't figure out the convoluted method I need to get back to a node that has the pointer I need. Even the link to that original article/post would be useful to me :) Google is giving me no joy. Edit: Jérémie pointed out that there is a fairly simple (and well known answer) if you have a parent pointer. While I now think he is correct about the original solution containing a parent pointer, I really wanted to solve the problem without it :) The refined requirements use this definition for the node: struct tree_node { int value; tree_node* left; tree_node* right; };

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• How to: StructureMap and configuration based on runtime parameters?

  - by user981375

  In a nutshell - I want to be able to instantiate object based on runtime parameters. In this particular case there are only two parameters but the problem is that I'm facing different permutations of these parameters and it gets messy. Here is the situation: I want to get an instance of an object specific to, say, given country and then, say, specific state/province. So, considering the US, there are 50 possible combinations. In reality it's less than that but that's the max. Think of it this way, I want to find out what's the penalty for smoking pot in a given country/state, I pass this information in and I get instantiated object telling me what it is. To the code (for reference only): interface IState { string Penalty { get; } } interface ICountry { IState State { get; set; } string Name { get; } } class BasePenalty : IState { virtual public string Penalty { get { return "Slap on a wrist"; } } } class USA : ICountry { public USA(IState state) { State = state; } public IState State { get; set; } public string Name { get { return "USA"; } } } class Florida: BasePenalty { public override string Penalty { get { return "Public beheading"; } } } // and so on ... I defined other states // which have penalties other than the "Slap on a wrist" How do I configure my container that when given country and state combination it will return the penalty? I tried combinations of profile and contextual binding but that configuration was directly proportional to the number of classes I've created. I have already gone thru trouble of defining different combinations. I'd like to avoid having to do the same during container configuration. I want to inject State into the Country. Also, I'd like to return UsaBasePenalty value in case state is not specified. Is that possible? Perhaps these is something wrong with the design.

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• Can I create a two-column layout that fluidly adapts to narrow windows?

  - by Brant Bobby

  I'm trying to design a page that has two columns of content, div#left and div#right. (I know these aren't proper semantic identifiers, but it makes explaining easier) The widths of both columns are fixed. Desired result - Wide viewport When the viewport is too narrow to display both side-by-side, I want #right to be stacked on top of #left, like this: Desired result - narrow viewport My first thought was simply to apply float: left to #left and float: right to #right, but that makes #right attach itself to the right side of the window (which is the proper behavior for float, after all), leaving an empty space. This also leaves a big gap between the columns when the browser window is really wide. Wrong - div#right is not flush with the left side of the viewport Wrong - div#right is not on top of div#left Applying float: left to both divs would result in the wrong one moving to the bottom when the window was too small. I could probably do this with media queries, but IE doesn't support those until version 9. The source order is unimportant, but I need something that works in IE7 minimum. Is this possible to do without resorting to Javascript?

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• cfdiv working in FF and Safari but does not show up in IE

  - by JS

  Within a form I have a button that launches a cfwindow, then presents a search screen for the user to make a selection. Once selection is made, the cfwindow closes and the selected content shows in the main page by being bound to a cfdiv. This all works fine in FF but the cfdiv doesn't show at all in IE. In IE, the cfwindow works, the select works, but then no bound page. I have tried setting bindonload and that made no difference (and I need it to be true if there is content that is pulled in via a query when it loads). All I have been able to find so far regarding this issue is setting bindonload to false and putting the cfdiv outside of the form but that's not possible in my current design. Here is a snippet which is inside of a larger form (and all necessary tags are cfimported). <td class="left" style="white-space:nowrap;"> <cfoutput>#n#</cfoutput>.&nbsp;<cfinput type="button" value="Select" name="x#n#Select#i#" onClick="ColdFusion.Window.create('x#n#Select#i#', 'Exercise Lookup', 'xSelect/xSelect.cfm?xNameVar=x#n#S#i#&window=x#n#Select#i#&workout=workout#i#', {x:100,y:100,height:500,width:720,modal:true,closable:true,draggable:true,resizable:true,center:true,initshow:true,minheight:200,minwidth:200 })" /> &nbsp; <cfdiv id="x#n#S#i#" tagName="x#n#S#i#" bind="url:xSelect/x.cfm"></cfdiv> <cfinput type="hidden" name="x#n#s#i#" value="#n#"> </td> Thanks for any help.

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• How to best manage multi-frame MovieClips with classes?

  - by Arms

  After switching to AS3, I've been having a hell of a time figuring out the best way to manage MovieClips that have UI elements spread across multiple frames with a single class. An example that I am working on now is a simple email form. I have a MovieClip with two frames: the 1st frame has the form elements (text inputs, submit button) the 2nd frame has a "thank you" message and a button to go back to the first frame (to send another email) In the library I have linked the MovieClip to a custom class (Emailer). My immediate problem is how do I assign a MouseEvent.CLICK event to the button on the 2nd frame? I should note at this point that I am trying to avoid putting code on the timeline (except for stop() calls). This is how I am 'solving' the problem now: Emailer registers an event listener for a frame change ( addEventListener("frame 2", onFrameChange) ) On the 2nd frame of the MovieClip I am calling dispatchEvent(new Event("frame 2")); (I would prefer to not have this code on the frame, but I don't know what else to do) My two complaints with this method are that, first I have calls to addEventListener spread out across different class methods (I would rather have all UI event listeners registered in one method), and second that I have to dispatch those custom "onFrameChange" events. The second complaint grows exponentially for MovieClips that have more than just 2 frames. My so called solution feels makes me feel dirty and makes my brain hurt. I am looking for any advice on what to do differently. Perhaps there's a design pattern I should be looking at? Should I swallow my pride and write timeline code even though the rest of my application is written in class files (and I abhor the Flash IDE code editor)? I absolutely LOVE the event system, and have no problem coding applications with it, but I feel like I'm stuck thinking in terms of AS2 when working with mutl-frame movieclips and code. Any and all help would be greatly appreciated.

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• What's the best practice for make username check like Twitter ?

  - by Space Cracker

  I develop registration form and it have username field, and it's required to be like twitter username check ( real time check ) .. i already develop as in every textbox key up I use jquery to pass textbox.Text to page that return if is username exist or not as following code : function Check() { var userName = $('#<%= TextBox1.ClientID %>').val(); if (userName.length < 3) { $('#checkUserNameDIV').html("user name must be between 3 and 20"); return; } $('#checkUserNameDIV').html('<img src="loader.gif" />'); //setTimeout("CheckExistance('" + userName + "')", 5000); CheckExistance(userName); } function CheckExistance(userName) { $.get( "JQueryPage.aspx", { name: userName }, function(result) { var msg = ""; if (result == "1") msg = "Not Exist " + '<img src="unOK.gif" />'; else if (result == "0") msg = "Exist" ; else if (result == "error") msg = "Error , try again"; $('#checkUserNameDIV').html(msg); } ); } but i don't know if is it the best way to do that ? specially i do check every keyup .. is there any design pattern for this problem or nay good practice for doing that ?

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• Lucene raise document score if sibling entity matches query

  - by Pitagoras

  I have the following design situation. I use hibernate search (lucene in the back). Tha application manages ITEMs which have title, description and tags. These are full text indexed. On the other hand, we have COLLECTION of ITEMs. The user can create a COLLECTION and add as many ITEMs as she wants. ITEMs can also belong to many COLLECTIONs. I have a boosted query so that search terms that appear in the tags are more important than in the title, and lastly in the description. But I need an additional matching criteria: for a given ITEM, it whould rank better if other documents in some COLLECTION where the ITEM belongs, also match the query. This is like to say: the title/tags/description of "fellow" items (i.e. items in some shared collection) make the item rank better. I was thinking that adding an ITEM to a COLLECTION would add something like "extra tags" to every other ITEM in the collection, being these extra tags the elements to match in the added ITEM. I feel a more clever solution lucene-wise should exists. Any ideas/pointers are welcome. Thanks.

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• Console Application Structure

  - by Paul Fox

  I've written several .Net Console Applications over the past 6 months and we have many more throughout different projects in our organization. I generally stick to the same standard format/structure for my Console Applications. Unfortunately, many of our console applications do not. I have been looking into ways of standardizing the structure of these Console Applications. I would also like to provide a framework for the basic structure of a Console Application and provide easy access to standard ways of handling things such as argument passing, logging, etc. Can anyone suggest Best Practices for addressing these concerns? I have been reading this MSDN article on Console Applications in .Net which suggests a Design Pattern for Console Apps. The example uses a Template Method pattern to handle some of the concerns I listed earlier. Two negatives of using this approach are listed in the article. Ending up with twice as many classes Having many simple, similar classes Can anyone suggest better, or more standard, ways of handling this? What about listing additional negatives with this approach?

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• How to tell if leaving iOS app entered foreground from fast-app switching or manually?

  - by JPK

  Is there a way to tell if an iOS app enters the foreground from fast-app switching or manually? I need to know by the time applicationWillEnterForeground is called, so some specific code can be executed (or not executed) depending on the condition in which the app entered the foreground. EDIT: It turned out that this was more of a design issue for me. I moved my code to applicationDidBecomeActive. I also added a BOOL property to the appDelegate called fastAppSwitching (probably the wrong name for it). I set this to YES in application:handleOpenURL and application:openURL:sourceApplication:annotation. Then I added the following code to application:didFinishLaunchingWithOptions: if (launchOptions) { self.fastAppSwitching = YES; } else { self.fastAppSwitching = NO; } In applicationDidBecomeActive, I used the following code: if (fastAppSwitching == YES) { self.fastAppSwitching = NO; //stop, don't go any further } else { ... } EDIT2: MaxGabriel makes a good point below: "Just a warning to others taking the solution described here, applicationDidBecomeActive: is called when the user e.g. ignores a phone call or text message, unlike applicationWillEnterForeground". This is actually also true for in-app purchases and Facebook in-app authorization (new in iOS 6). So, with some further testing, this is the current solution: Add a new Bool called passedThroughWillEnterForeground. In applicationWillResignActive: self.passedThroughWillEnterForeground = NO; In applicationDidEnterBackground: self.passedThroughWillEnterForeground = NO; In applicationWillEnterForeground: self.passedThroughWillEnterForeground = YES; In applicationDidBecomeActive: if (passedThroughWillEnterForeground) { //we are NOT returning from 6.0 (in-app) authorization dialog or in-app purchase dialog, etc //do nothing with this BOOL - just reset it self.passedThroughWillEnterForeground = NO; } else { //we ARE returning from 6.0 (in-app) authorization dialog or in-app purchase dialog - IE //This is the same as fast-app switching in our book, so let's keep it simple and use this to set that self.fastAppSwitching = YES; } if (fastAppSwitching == YES) { self.fastAppSwitching = NO; } else { ... } EDIT3: I think we also need a bool to tell if app was launched from terminated.

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• help with delete where not in query

  - by kralco626

  I have a lookup table (##lookup). I know it's bad design because I'm duplicating data, but it speeds up my queries tremendously. I have a query that populates this table insert into ##lookup select distinct col1,col2,... from table1...join...etc... I would like to simulate this behavior: delete from ##lookup insert into ##lookup select distinct col1,col2,... from table1...join...etc... This would clearly update the table correctly. But this is a lot of inserting and deleting. It messes with my indexes and locks up the table for selecting from. This table could also be updated by something like: delete from ##lookup where not in (select distinct col1,col2,... from table1...join...etc...) insert into ##lookup (select distinct col1,col2,... from table1...join...etc...) except if it is already in the table The second way may take longer, but I can say "with no lock" and I will be able to select from the table. Any ideas on how to write the query the second way?

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• Where to start to create an HTML website with 2 tables read from csv files using anything but php

  - by CodingIsAwesome

  I want to design a website which displays on loading two tables each with it's respective data from a csv file. Then every minute the website automatically refreshes. This problem seems so simple! But yet the solution eludes me. All of the files will be contained in 1 directory, not on a server but on a local machine. Such as sitting on the desktop. I understand if I use javascript I have to use ADO, and I'm still trying to work out how to use ASP. I am new with both languages. So far the only restriction is that I can't use PHP. So the jist so far as I can think right now is: 1. read the file 2. place the file into an array by splitting at the commas 3. write the array into td's ????? 4. then print all this out into a div ???? I have googled my heart out and can't seem to find what I'm looking for. or even piece together what I'm looking for. Everything with javascript and ADO's leads me to dead ends, I can't find anything on ASP that is helpful. Could someone please write up some sample code for a resource? Or have a better solution?

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• .NET security mechanism to restrict access between two Types in the same project?

  - by jdk

  Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project. Note: I'm not talking about access modifiers to hide members of a Type from another type - I mean to hide the Type itself. Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the same ASP.NET Website project. In other words I want to fake the layers and have some kind of security mechanism around each layer to prevent it from accessing another. Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. Even something that restricts one namespace from accessing another. I'm unsure the final form it might take. If this were C++ I'd likely be using friend to make as solution, which doesn't translate to C# internal in this case although they're often compared. I don't really care whether the solution actually hides Types from each other or just makes them inaccessible; however I don't want to lock down one Type from all others, another reason access modifiers are not a solution. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ...

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• Dynamic content in a Gridview

  - by mariki

  I have a gridview with couple of columns,I want to achieve the following: If user is NOT authorized display normal columns. If user IS authorized: set mouseover event for first column text and display some buttons (that are not available for NOT authorized users) in a second column when user hover over(using javascript) the first column. I am have 2 difficulties: The first one where and when should I create the buttons? I have 2 options, I can create those button on design time, in gridviews template and just set Visible value to false and then in codebehind set it to true if user is authorized. The second option would be creating this buttons dynamically in gridview_RowCreated event (or any other event) if user is authorized. The Second difficulty is setting the javascript event to show the buttons, the event should be added only if user is authorized! Note that event and buttons should have some kind of id match for Javascript function to know what should it hide/unhide when event is triggered. What should I do, what is the best practice? I know this is a long question, but please try to help :)

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• Theme-aware XAML resources in a WP7 project

  - by SandRock

  I'm making a Windows Phone 7 application and I'm a bit confused with dark/light themes. With a panorama, you very often set a background image. The issue is it's very hard to make a picture which is right for both dark and light themes. How are we supposed to proceed? Is there a way to force a dark/light theme for a panorama? This will avoid making theme-specific panorama background pictures. Then how do I do? I found xaml files in C:\Program Files (x86)\Microsoft SDKs\Windows Phone\v7.0\Design. If this is a right way to proceed, how can I import them for my panorama? Or if there's no way (or if it's wrong) to force a dark/light theme: how to write conditional XAML to set correct resources? Now I have the following XAML which is fine with the dark theme: <ImageBrush x:Key="PageBackground" ImageSource="Resources/PageBackground.png" Stretch="None" /> <ImageBrush x:Key="PanoramaBackground" ImageSource="Resources/PanoramaBackground.png" Stretch="None" /> But when I use a light theme, black controls and black texts are hard to read with my dark background pictures. So I made different pictures that I can use this way: <ImageBrush x:Key="PageBackground" ImageSource="Resources/PageBackgroundLight.png" Stretch="None" /> <ImageBrush x:Key="PanoramaBackground" ImageSource="Resources/PanoramaBackgroundLight.png" Stretch="None" /> Now my issue is to make XAML conditionnal to declare the right thing depending on the current theme. I found no relevant way on the Internet. I would prefer not to use code or code-behind for that because I believe XAML is able to do this (I just don't know how).

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• Codeigniter - Active record - sql - complex join

  - by Jack

  I have a function that retrieves all tags from a table: function global_popular_tags() { $this->db->select('tags.*, COUNT(tags.id) AS count'); $this->db->from('tags'); $this->db->join('tags_to_work', 'tags.id = tags_to_work.tag_id'); $this->db->group_by('tags.id'); $this->db->order_by('count', 'desc'); $query = $this->db->get()->result_array(); return $query; } I have another table called 'work'. The 'work' table has a 'draft' column with values of either 1 or 0. I want the COUNT(tags.id) to take into account whether the work with the specific tag is in draft mode (1) or not. Say there are 10 pieces of work tagged with, for example, 'design'. The COUNT will be 10. But 2 of these pieces of work are in draft mode, so the COUNT should really be 8. How do I manage this?

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• How to be a better software designer

  - by Bmw

  I feel as if I am a hack programmer. I do things over and over again until they finally work. I copy/paste code. I don't think about why something makes sense, if it works I go with it. I have my undergraduate in computer science, and I've done this the entire time. Somehow I made it through the degree by doing this and now I'm in my second year of programming professionally and I am still able to do this and get away with it. Here's the thing, I don't want to be this way anymore. I am not proud of the work I do, I feel like I'm just a copy/paste programmer. How do I become better? I want to be able to design something on my own without copying code. Have you ever been in this situation, if so how did you move beyond it to become a better programmer? To add some background about myself, I started as an asp.net c# programmer, now I'm doing vbscript (which actually makes my tendency to copy/paste/hack a lot worse I must say!) with classic asp…

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• To NOLOCK or NOT to NOLOCK, that is the question

  - by Limey

  Hi all, This is really more of a discussion than a specific question about nolock. I took over an app recently that almost every query (and there are lots of them) has the nolock option on them. Now I am pretty new to SQL server (used Oracle for 10 years) but yet I find this pretty disturbing. So this weekend I was talking with one of my friends who runs a rather large ecommerce site (name will be withheld to protect the guilty) and he says he has to do this with all of his SQL servers cause he will always end in deadlocks. Is this just a huge short fall with SQL server? Is this just a failure in the DB design (mine is not 3rd level, but its close) Is anybody out there running an SQL server app without nolocks? These are issues that Oracle handles better with more grandulare recordlocks. Is SQL server just not able to handle big loads? Is there some better workaround than reading uncommited data? I would love to hear what people think. Thanks

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• Why use shorter VARCHAR(n) fields?

  - by chryss

  It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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• Are reads and (transactional) writes faster for entities of the same group than otherwise?

  - by indiehacker

  What advantage is there to designing child-parent relationships, which allow us to do writes in transactions, when there is never a real concern for consistency and contention and those sort of more complex issues? Does it make writes and reads faster? Consider my situation where there are many .png images that are referenced to one mosaic layer, and these .png images are written just once by a single user. The user can design many mosaic layers and her mosaic layers and referenced image entities are never changed/updated, they are just deleted some time in the future. Other users can come to the web project site and interactively view the mosaic layer as different layouts/configurations of the images as they play (query) with different criteria. So reads should be very fast. So there is no real worry of contention, or users conflicting with one another with writing new image entities. And because of that I am assuming there is no "requirement" for the .png image entities to be grouped by their same mosaic layer in child-parent relationship. However, perhaps, since the documentation says they are stored close to one another, if the many image entities were grouped as children to a single mosaic layer parent than this has the advantage that the writing (in transaction) and reading will happen much faster?

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