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  • MS Access 07 - Q re lookup column vs many-to-many; Q re checkboxes in many-to-many forms

    - by TBinLondon
    Hello, I'm creating a database with Access. This is just a test database, similar to my requirements, so I can get my skills up before creating one for work. I've created a database for a fictional school as this is a good playground and rich data (many students have many subjects have many teachers, etc). Question 1 What is the difference, if any, between using a Lookup column and a many-to-many associate table? Example: I have Tables 'Teacher' and 'Subject'. Many teachers have many subjects. I can, and have, created a table 'Teacher_Subject' and run queries with this. I have then created a lookup column in teachers table with data from subjects. The lookup column seems to take the place of the teacher_subject table. (though the data on relationships is obviously duplicated between lookup table and teacher_subject and may vary). Which one is the 'better' option? Is there a snag with using lookup tables? (I realize that this is a very 'general' question. Links to other resources and answers saying 'that depends...' are appreciated) Question 2 What attracts me to lookup tables is the following: When creating a form for entering subjects for teachers, with lookup I can simply create checkboxes and click a subject for a teacher 'on' or 'off'. Each click on/off creates/removes a record in the lookup column (which replaces teacher_subject). If I use a form from a query from teacher subject with teacher as main form and subject as subform I run into this problem: In the subform I can either select each subject that teacher has in a bombo box, i.e. click, scroll down, select, go to next row, click, scroll down, etc. (takes too long) OR I can create a list box listing all available subjects in each row but allowing me to select only one. (takes up too much space). Is it possible to have a click on/off list box for teacher_subject, creating/removing a record there with each click? Note - I know zero SQL or VB. If the correct answer is "you need to know SQL for this" then that's cool. I just need to know. Thanks!

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  • get-wmiobject sql join in powershell - trying to find physical memory vs. virtual memory of remote s

    - by Willy
    get-wmiobject -query "Select TotalPhysicalMemory from Win32_LogicalMemoryConfiguration" -computer COMPUTERNAME output.csv get-wmiobject -query "Select TotalPageFileSpace from Win32_LogicalMemoryConfiguration" -computer COMPUTERNAME output.csv I am trying to complete this script with an output as such: Computer Physical Memory Virtual Memory server1 4096mb 8000mb server2 2048mb 4000mb

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  • Preprocessor #define vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • C++ pimpl idiom wastes an instruction vs. C style?

    - by Rob
    (Yes, I know that one machine instruction usually doesn't matter. I'm asking this question because I want to understand the pimpl idiom, and use it in the best possible way; and because sometimes I do care about one machine instruction.) In the sample code below, there are two classes, Thing and OtherThing. Users would include "thing.hh". Thing uses the pimpl idiom to hide it's implementation. OtherThing uses a C style – non-member functions that return and take pointers. This style produces slightly better machine code. I'm wondering: is there a way to use C++ style – ie, make the functions into member functions – and yet still save the machine instruction. I like this style because it doesn't pollute the namespace outside the class. Note: I'm only looking at calling member functions (in this case, calc). I'm not looking at object allocation. Below are the files, commands, and the machine code, on my Mac. thing.hh: class ThingImpl; class Thing { ThingImpl *impl; public: Thing(); int calc(); }; class OtherThing; OtherThing *make_other(); int calc(OtherThing *); thing.cc: #include "thing.hh" struct ThingImpl { int x; }; Thing::Thing() { impl = new ThingImpl; impl->x = 5; } int Thing::calc() { return impl->x + 1; } struct OtherThing { int x; }; OtherThing *make_other() { OtherThing *t = new OtherThing; t->x = 5; } int calc(OtherThing *t) { return t->x + 1; } main.cc (just to test the code actually works...) #include "thing.hh" #include <cstdio> int main() { Thing *t = new Thing; printf("calc: %d\n", t->calc()); OtherThing *t2 = make_other(); printf("calc: %d\n", calc(t2)); } Makefile: all: main thing.o : thing.cc thing.hh g++ -fomit-frame-pointer -O2 -c thing.cc main.o : main.cc thing.hh g++ -fomit-frame-pointer -O2 -c main.cc main: main.o thing.o g++ -O2 -o $@ $^ clean: rm *.o rm main Run make and then look at the machine code. On the mac I use otool -tv thing.o | c++filt. On linux I think it's objdump -d thing.o. Here is the relevant output: Thing::calc(): 0000000000000000 movq (%rdi),%rax 0000000000000003 movl (%rax),%eax 0000000000000005 incl %eax 0000000000000007 ret calc(OtherThing*): 0000000000000010 movl (%rdi),%eax 0000000000000012 incl %eax 0000000000000014 ret Notice the extra instruction because of the pointer indirection. The first function looks up two fields (impl, then x), while the second only needs to get x. What can be done?

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  • When to rewrite vs. upgrade?

    - by MrGumbe
    All custom legacy software needs changing, or so say our users. Sometimes they want a feature or two added and all that is necessary to change a bit of code, add a control, or some other minor upgrade task. Sometimes they want to ditch their error-prone VB5 desktop solution and rewrite the whole thing as a rich Web 2.0 ASP.NET MVC application. More often, however, the scope of changes to legacy functionality lies somewhere between these two extremes. What rules of thumb to you use to decide whether you should upgrade an existing application or start from scratch?

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  • Singletons vs. Application Context in Android?

    - by mschonaker
    Recalling this post enumerating several problems of using singletons and having seen several examples of Android applications using singleton pattern, I wonder if it's a good idea to use Singletons instead of single instances shared through global application state (subclassing android.os.Application and obtaining it through context.getApplication()). What advantages/drawbacks would have both mechanisms? To be honest, I expect the same answer in this post http://stackoverflow.com/questions/2709071/singleton-pattern-with-web-application-not-a-good-idea but applied to Android. Am I correct? What's different in DalvikVM otherwise? EDIT: I would like to have opinions on several aspects involved: Synchronization Reusability Testing Thanks in advance.

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  • IList<T> vs IEnumerable<T>. What is more efficient IList<T> or IEnumerable<T>

    - by bigb
    What is more efficient way to make methods return IList<T> or IEnumerable<T>? IEnumerable<T> it is immutable collection but IList<T> mutable and contain a lot of useful methods and properties. To cast IList<T> to IEnumerable<T> it is just reference copy: IList<T> l = new List<T>(); IEnumerable<T> e = l; To cast IEnumerable<T> to List<T> we need to iterate each element or to call ToList() method: IEnumerable<T>.ToList(); or may pass IEnumerable<T> to List<T> constructor which doing the same iteration somewhere within its constructor. List<T> l = new List<T>(e); Which cases you think is more efficient? Which you prefer more in your practice?

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  • Access as a front-end to SQL Server - ADO vs DAO?

    - by webworm
    I have a project that will be using Access 2003 as the font-end and the data being stored in SQL Server. Access will connect to SQL Server via linked tables with all the database logic (stored procedures, views) within SQL Server. Given this setup, would it be better to use ADO or DAO within Access? Is it just a matter of preference or is one more suited to Access as a font-end and SQL Server as the data store? Especially when using linked tables. Thanks.

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  • VS 2010 Error “Object reference not set to an instance of an object” when adding Service Reference f

    - by Andy
    I have a VS2010 (RTM) solution which contains: WCF Service project Console WCF client project Class project for DataContracts and members Class project for some simple classes I successfully added a service reference in the console client project and ran the client. I then did a long dev cycle repeatedly modifying the service then updating console service reference. I then changed the namespace and assembly names for the projects as well as the .cs using references and app.config. I of course missed some things as it would not build so I eventually removed the project references and the service reference, cleaned and built successfully. I then attempted to add the service reference again, it discovered it but threw the “Object reference not set to an instance of an object” when OK'ing. Fix in answer below...

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  • HTML 5 <video> tag vs Flash video. What are the pros and cons?

    - by Vilx-
    Seems like the new <video> tag is all the hype these days, especially since Firefox now supports it. News of this are popping up in blogs all over the place, and everyone seems to be excited. But what about? As much as I searched I could not find anything that would make it better than the good old Flash video. In fact, I see only problems with it: It will still be some time before all the browsers start supporting it, and much more time before most people upgrade; Flash is available already and everyone has it; You can couple Flash with whatever fancy UI you want for controlling the playback. I gather that the tag will be controllable as well (via JavaScript probably), but will it be able to go fullscreen? The only two pros for a <video> tag that I can see are: It is more "semantic" - which probably holds no importance to a whole lot of people, including me; It is not dependent on a single commercial 3rd party entity (Adobe) - which I also don't see as a compelling reason to switch, because free players and video converters are already available, and Adobe is not hindering the whole process in any way (it's not in their interests even). So... what's the big deal? Added: OK, so there is one more Pro... maybe. Support for mobile devices. Hard to say though. A number of thoughts race through my head about the subject: How many mobile devices are actually able to decode video at a decent speed anyway, Flash or otherwise? How long until mainstream mobile devices get the <video> support? Even if it is available through updates, how many people actually do that? How many people watch videos on web pages on their mobile phones at all? As for the semantics part - I understand that search engines might be able to detect videos better now, but... what will they do with them anyway? OK, so they know that there is a video in the page. And? They can't index a video! I'd like some more arguments here. Added: Just thought of another Cons. This opens up a whole new area of cross-browser incompatibility. HTML and CSS is quite messy already in this aspect. Flash at least is the same everywhere. But it's enough for at least one major browser vendor to decide against the <video> tag (can anyone say "Internet Explorer"?) and we have a nice new area of hell to explore. Added: A Pro just came in. More competition = more innovation. That's true. Giving Adobe more competition will probably force them to improve Flash in areas it has been lacking so far. Linux seems to be a weak spot for it, cited by many.

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  • Using a trigger to record audit information vs. stored procedure

    - by Germ
    Suppose you have the following... An ASP.NET web application that calls a stored procedure to delete a record. The table has a trigger on it that will insert an audit entry each time a record is deleted. I want to be able to record in the audit entry the username of who deleted the record. What would be the best way to go about achieving this? I know I could remove the trigger and have the delete stored procedure insert the audit entry prior to deleting but are there any other recommeded alternative? If a username was passed as a parameter to the delete stored procedure, is there anyway to get this value in the trigger that's excuted when the record is deleted? I'm just throwing this out there...

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  • MySQL PHP | "SELECT FROM table" using "alphanumeric"-UUID. Speed vs. Indexed Integer / Indexed Char

    - by dropson
    At the moment, I select rows from 'table01' using: SELECT * FROM table01 WHERE UUID = 'whatever'; The UUID column is a unique index. I know this isn't the fastest way to select data from the database, but the UUID is the only row-identifier that is available to the front-end. Since I have to select by UUID, and not ID, I need to know what of these two options I should go for, if say the table consists of 100'000 rows. What speed differences would I look at, and would the index for the UUID grow to large, and lag the DB? Get the ID before doing the "big" select 1. $id = "SELECT ID FROM table01 WHERE UUID = '{alphanumeric character}'"; 2. $rows = SELECT * FROM table01 WHERE ID = $id; Or keep it the way it is now, using the UUID. 1. SELECT FROM table01 WHERE UUID '{alphanumeric character}'; Side note: All new rows are created by checking if the system generated uniqueid exists before trying to insert a new row. Keeping the column always unique. The "example" table. CREATE TABLE Table01 ( ID int NOT NULL PRIMARY KEY, UUID char(15), name varchar(100), url varchar(255), `date` datetime ) ENGINE = InnoDB; CREATE UNIQUE INDEX UUID ON Table01 (UUID);

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  • Rapid Web Application Development ASP.net vs. Open Source Platforms

    - by Yaaqov
    Good morning - I'm an intermediate-level developer who wants to build on online data-driven app (CRUD with a few calculations and basic HTML form inputs, nothing fancy) that keeps track of user sessions, and looks "professional" (or at least not "homemade"). I'm looking to development something with the look-and-feel that users get from sites like: http://www.datamasher.org/ http://www.thisweknow.org/ (About page says it was made with Ruby on Rails, which I'm unfamiliar with) (stackoverflow.com) Any pointers on whether I should just go the Miscrosoft route, and develop in ASP.net with WebForms, or if there's a quick qay to do this kind of development (with a WYSIWYG environment) on an open-source platform? I'm willing to learn, if it's somethat I can use to quickly drag/drop, add code, and publish online. Templates would be a plus, too. I apologize is the question seems a bit vague.

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  • Address of array vs. address of array[0] - C language

    - by user324994
    My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = malloc(BUFF_SIZE); printf("The address of mallocbuff is %d\n", &mallocbuff); printf("The address of mallocbuff[0] is %d\n", &mallocbuff[0]); } &mallocbuff is the same address every time I run it. &mallocbuff[0] is some random address every time. I was expecting the addresses to match each other. Can anyone explain why this isn't the case?

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  • Can you step into specific properties in VS 2010?

    - by cyclotis04
    I know that you can either step into every property or not step into every property, but I would really like to be able to step into a specific property, and not the rest. Is this possible? (I also know I can use keyboard commands, but I'm asking if there's a more permanent solution.) I have a lot of properties and my setters do important things, so it's silly to step over them, but most of my getters are pointless. I'm looking for something like: public string ImportantProperty { get { return _importantProperty; } [DebuggerStepThrough(false)] set { if (this.State != ConnectionState.Closed) throw new InvalidOperationException( "Important Property cannot be changed unless This is closed."); if (ImportantProperty == value) return; _importantProperty = value; OnImportantPropertyChanged(new EventArgs()); } } Unfortunately, I can't find anything that will act like [DebuggerStepThrough(false)] and I must resort to turning off property step-over and putting [DebuggerStepThrough] everywhere I don't want to step-through.

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  • launch the emulator, I only see the black window with the string 'ANDROID", and no more desktop and

    - by Jiawelin
    Dear experts, I download the Android code and "make sdk" to build out my own SDK, but the emulator from this SDK does not work well -- it only shows the black window with the "ANDROID" string, but I can't see any desktop picture or any applications. what's wrong here? anyone could please provide me a hint? Thanks a lot. I use the command: $./emulator @jiawelin -debug all and the last output message is: emulator: android_hw_control_init: hw-control qemud handler initialized

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  • Why are there performance differences when a SQL function is called from .Net app vs when the same c

    - by Dan Snell
    We are having a problem in our test and dev environments with a function that runs quite slowly at times when called from an .Net Application. When we call this function directly from management studio it works fine. Here are the differences when they are profiled: From the Application: CPU: 906 Reads: 61853 Writes: 0 Duration: 926 From SSMS: CPU: 15 Reads: 11243 Writes: 0 Duration: 31 Now we have determined that when we recompile the function the performance returns to what we are expecting and the performance profile when run from the application matches that of what we get when we run it from SSMS. It will start slowing down again at what appear to random intervals. We have not seen this in prod but they may be in part because everything is recompiled there on a weekly basis. So what might cause this sort of behavior?

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  • Using CompareTo() on different .NET types (e.g. int vs. double)

    - by Yossin
    Hi, I've got a static method that accepts two object type variables and runs the CompareTo() method: public static int Compare(Object objA, Object objB) { return (((IComparable)objA).CompareTo(objB)); } Problem is that CompareTo() throws an exception when trying to compare between different types (e.g. int and double). Does any one know of a better way in C#, to compare between two different types? Or a workaround to this problem? Thanks

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  • memcached vs. internal caching in PHP?

    - by waitinforatrain
    Hey, I'm working on some old(ish) software in PHP that maintains a $cache array to reduce the number of SQL queries. I was thinking of just putting memcached in its place and I'm wondering whether or not to get rid of the internal caching. Would there still be a worthwihle performance increase if I keep the internal caching, or would memcached suffice?

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