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  • Database structure for storing Bank-like accounts and transactions

    - by user1241320
    We're in the process of adding a bank-like sub-system to our own shop. We already have customers, so each will be given a sort of account and transactions of some kind will be possible (adding to the account or subtracting from it). So we at least need the account entity, the transaction one and operations will then have to recalculate overall balances. How would you structure your database to handle this? Is there any standard bank system have to use that I could mock? By the way, we're on mysql but will also look at some nosql solution for performance boost.

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  • Invoicing vs Quoting or Estimating

    - by FreshCode
    If invoices can be voided, should they be used as quotations? I have an Invoices tables that is created from inventory associated with a Job or Order. I could have a Quotes table as a halfway-house between inventory and invoices, but it feels like I would have duplicate data structures and logic just to handle an "Is this a quote?" bit. From a business perspective, quotes are different from invoices: a quote is sent prior to an undertaking and an invoice is sent once it is complete and payment is due, but how to represent this in my repository and model. What is an elegant way to store and manage quotes & invoices in a database? Edit: indicated Job === Order for this particular instance.

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  • If we make a number every millisecond, how much data would we have in a day?

    - by Roger Travis
    I'm a bit confused here... I'm being offered to get into a project, where would be an array of certain sensors, that would give off reading every millisecond ( yes, 1000 reading in a second ). Reading would be a 3 or 4 digit number, for example like 818 or 1529. This reading need to be stored in a database on a server and accessed remotely. I never worked with such big amounts of data, what do you think, how much in terms of MBs reading from one sensor for a day would be?... 4(digits)x1000x60x60x24 ... = 345600000 bits ... right ? about 42 MB per day... doesn't seem too bad, right? therefor a DB of, say, 1 GB, would hold 23 days of info from 1 sensor, correct? I understand that MySQL & PHP probably would not be able to handle it... what would you suggest, maybe some aps? azure? oracle? ... Thansk!

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  • Join Where Rows Don't Exist or Where Criteria Matches...?

    - by Greg
    I'm trying to write a query to tell me which orders have valid promocodes. Promocodes are only valid between certain dates and optionally certain packages. I'm having trouble even explaining how this works (see psudo-ish code below) but basically if there are packages associated with a promocode then the order has to have one of those packages and be within a valid date range otherwise it just has to be in a valid date range. The whole "if PrmoPackage rows exist" thing is really throwing me off and I feel like I should be able to do this without a whole bunch of Unions. (I'm not even sure if that would make it easier at this point...) Anybody have any ideas for the query? if `OrderPromoCode` = `PromoCode` then if `OrderTimestamp` is between `PromoStartTimestamp` and `PromoEndTimestamp` then if `PromoCode` has packages associated with it //yes then if `PackageID` is one of the specified packages //yes code is valid //no invalid //no code is valid Order: OrderID* | OrderTimestamp | PackageID | OrderPromoCode 1 | 1/2/11 | 1 | ABC 2 | 1/3/11 | 2 | ABC 3 | 3/2/11 | 2 | DEF 4 | 4/2/11 | 3 | GHI Promo: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* ABC | 1/1/11 | 2/1/11 ABC | 3/1/11 | 4/1/11 DEF | 1/1/11 | 1/11/13 GHI | 1/1/11 | 1/11/13 PromoPackage: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* | PackageID* ABC | 1/1/11 | 2/1/11 | 1 ABC | 1/1/11 | 2/1/11 | 3 GHI | 1/1/11 | 1/11/13 | 1 Desired Result: OrderID | IsPromoCodeValid 1 | 1 2 | 0 3 | 1 4 | 0

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  • Designing a frontend/backend architecture

    - by wrp
    What are some good information sources on designing programs with a client/server architecture? This is for development of a desktop application, not a Web service. The only books I have found on client/server apps deal with the case of a thin client connecting to a remote database. Two good examples of what I mean are Mathematica and SuperCollider. I'm looking for platform- and language-agnostic discussion of the issues in developing a frontend/backend system. Especially useful topics would be allocation of responsibilities and options for message passing.

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  • what is the easiest way to do this function in c# ?

    - by From.ME.to.YOU
    Hello let say that we have an array [5,5] 01,02,03,04,05 06,07,08,09,10 11,12,13,14,15 16,17,18,19,20 21,22,23,24,25 the user should send 2 values to the function (start,searchFOR) for example (13,25) the function should search for that value in this way 07,08,09 12, ,14 17,18,19 if the value is n't found in this level it will goes a level higher 01,02,03,04,05 06, , , ,10 11, , , ,15 16, , , ,20 21,22,23,24,25 if the array is bigger than this and the value didn't found it will go to a level higher Thanks for your help

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  • When using a HiLo ID generation strategy, what types should be used to hold Ids?

    - by UpTheCreek
    I'm asking this from a c#/NHibnernate perspective, but it's generally applicable. The concern is that the HiLo strategy goes though id's pretty quickly, and for example a low record-count table (Such as Users) is sharing from the same set of id's as a high record-count table (Such as comments). So you can potentially get to high numbers quicker that with other strategies. So what do people recommend? Code side: int/uint/long/ulong? DBSide: int/bigint? My feeling is to go with longs and bigingts, but would like a sanity check :)

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  • Would ViewModels fit in the Model View Presenter pattern?

    - by Jonn
    Having used ViewModels in MVC, I was wondering if applying the same to the MVP pattern is practical. I only have a few considerations, one being that MVP is already fairly hard to implement (with all the additional coding, not much on the seeming complexity) or that ViewModels already have a slightly similar way of modeling data or entities. Would adding another layer in the form of ViewModels be redundant or is it a logical abstraction that I, as one implementing the MVP pattern, should adhere to?

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  • What are the lengths/limits C preprocessor as a language creation tool? Where can I learn more about

    - by Weston C
    In his FAQ @ http://www2.research.att.com/~bs/bs_faq.html#bootstrapping, Bjarne Stroustrup says: To build [Cfront, the first C++ compiler], I first used C to write a "C with Classes"-to-C preprocessor. "C with Classes" was a C dialect that became the immediate ancestor to C++... I then wrote the first version of Cfront in "C with Classes". When I read this, it piqued my interest in the C preprocessor. I'd seen its macro capabilities as suitable for simplifying common expressions but hadn't thought about its ability to significantly add to syntax and semantics on the level that I imagine bringing classes to C took. So now I have a couple of questions on my mind: 1) Are there other examples of this approach to bootstrapping a language off of C? 2) Is the source to Stroustrup's original work available anywhere? 3) Where could I learn more about the specifics of utilizing this technique? 4) What are the lengths/limits of that approach? Could one, say, create a set of preprocessor macros that let someone write in something significantly Lisp/Scheme like?

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  • Pattern for null settings

    - by user21243
    Hi, I would like to hear your thoughts and ideas about this one. in my application i have controls that are binded to objects properties. but.. the controls always looks like that: a check box, label that explain the settings and then the edited control (for ex: text box) when unchecking the checkbox i disable the text box (using binding) when the checkbox is unchecked i want the property to contain null, and when it is checked i would like the property to contain the text box's text. Of course text box can be NumericUpDown, ComboBox, DatePicker etc.. Do you have any smart way of doing it using binding or do i have to do everything on code; I really would like to a build a control that supports that and re-use it all over Ideas? Thanks,

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  • Travelling Salesman Problem Constraint Representation

    - by alex25
    Hey! I read a couple of articles and sample code about how to solve TSP with Genetic Algorithms and Ant Colony Optimization etc. But everything I found didn't include time (window) constraints, eg. "I have to be at customer x before 12am)" and assumed symmetry. Can somebody point me into the direction of some sample code or articles that explain how I can add constraints to TSP and how I can represent those in code. Thanks!

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  • Passing an array for setting variable

    - by mathk
    Hi, I often see this idiom when reading php code: public function __construct($config) { if (array_key_exists('options', $config)) { ... } if (array_key_exists('driver_options', $config)) { ... } } Here I am concern with the way the parameter is used. If I were in lisp I would do: (defun ct (&key options driver_options) (do-something-with-option-and-driver_option)) But since I am in PHP I would rather have a constructor that take a list of parameter and let them be null if there a not require. So what do you guys think about having an array as parameter in other to do some initialization-or-whatever? In other to answer you have to take in account the point of view of the user of the function and the designer of the API. Also have you ever heard this has a code-smell? thanks

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  • If as assert fails, is there a bug?

    - by RichAmberale
    I've always followed the logic: if assert fails, then there is a bug. Root cause could either be: Assert itself is invalid (bug) There is a programming error (bug) (no other options) I.E. Are there any other conclusions one could come to? Are there cases where an assert would fail and there is no bug?

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  • some confusions to singleton pattern in PHP

    - by SpawnCxy
    Hi all, In my team I've been told to write resource class like this style: class MemcacheService { private static $instance = null; private function __construct() { } public static function getInstance($fortest = false) { if (self::$instance == null) { self::$instance = new Memcached(); if ($fortest) { self::$instance->addServer(MEMTEST_HOST, MEMTEST_PORT); } else { self::$instance->addServer(MEM_HOST, MEM_PORT); } } return self::$instance; } } But I think in PHP resource handles will be released and initialized again every time after a request over. That means MemcacheService::getInstance() is totally equal new Memcached() which cannot be called singleton pattern at all. Please correct me if I'm wrong. Regards

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  • Working with foreign keys - cannot insert

    - by Industrial
    Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that is enforced with foreign keys relations? Thanks! Updated description: Products ---------------------------- id | type ---------------------------- 0 | 0 1 | 3 ProductsToCategories ---------------------------- productid | categoryid ---------------------------- 0 | 0 1 | 1 Product table has following structure CREATE TABLE IF NOT EXISTS `alpha`.`products` ( `id` MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT , `type` TINYINT(2) UNSIGNED NOT NULL DEFAULT 0 , PRIMARY KEY (`id`) , CONSTRAINT `prodsku` FOREIGN KEY (`id` ) REFERENCES `alpha`.`productsToSku` (`product` ) ON DELETE CASCADE, ON UPDATE CASCADE) ENGINE = InnoDB;

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  • Is it OK to re-create many SQL connections (SQL 2008)

    - by Mr. Flibble
    When performing many inserts into a database I would usually have code like this: using (var connection = new SqlConnection(connStr)) { connection.Open(); foreach (var item in items) { var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } I now want to shard the database and therefore need to choose the connection string based on the item being inserted. This would make my code run more like this foreach (var item in items) { connStr = GetConnectionString(item); using (var connection = new SqlConnection(connStr)) { connection.Open(); var cmd = new SqlCommand("INSERT ...") cmd.ExecuteNonQuery(); } } Which basically means it's creating a new connection to the database for each item. Will this work or will recreating connections for each insert cause terrible overhead?

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  • Why should GoTos be bad?

    - by lisn
    I'm using gotos and a lot of them. C++, PHP or COBOL - I use them on nearly all occasions where everybody else would use functions or even classes. Yet my code is Clear Maintainable Bug-free Fast So why does everybody I meet tell me about how bad gotos are? Are there any facts that show that they are "bad"?

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  • PHP Frontpage/Page controller

    - by atno
    I using the following as Frontpage/Page Controller(s) and it's working ok so far, except two problems I'm facing which as you can see are the $pages array and the switch, which are actually much much longer as the one I've pasted here. Everytime there is a need for a new page controller I have to add it to $pages array and to switch which makes that list very long. How would you overcome this problem and do you see any other improvement on this code? loadLogic() in page controllers it is used to get functions under pages/controllername/logic/function.php. Frontpage Controller - index.php: include 'common/common.php'; if(!isset($_GET['p']) OR $_GET['p'] == ''){ $_GET['p'] = 'home'; header('Location: index.php?p=home'); } $pages = array('home','register','login','logout','page1','page2','page3'); $_GET['p'] = trim($_GET['p']); if(isset($_GET['p'])){ if(in_array($_GET['p'], $pages)){ switch ($_GET['p']) { case 'home': include 'home.php'; break; case 'register': include 'register.php'; break; case 'login': include 'login.php'; break; case 'logout': include 'logout.php'; break; case 'page1': include 'page1.php'; break; case 'page2': include 'page2.php'; break; case 'page3': include 'page3.php'; break; } }else{ echo '404!'; } } Page Controller - {home,register,login,logout,page1,page2,page3}.php: include 'tpl/common/header.php'; contentStart(); if(isset($_SESSION['logged'])){ loadLogic('dashboard'); }else{ loadLogic('nologin'); } //Display login form in logic page instead links // if(!isset($_SESSION['logged'])){ contentEnd(); loadLogic('nologinForm'); }else{ contentEnd(); include'tpl/common/rcol.php'; } include 'tpl/common/footer.php'; function loadLogic(): function loadLogic($logic) { $path = dirname(__DIR__) . '/pages'; $controller = preg_split('/&/',$_SERVER['QUERY_STRING']); $controller = trim($controller[0],"p="); $logicPath = 'logic'; $logic = $logic . '.php'; $err = 0; $logicFullPath = $path.'/'.$controller.'/'.$logicPath.'/'.$logic; if($err == '0'){ include "$logicFullPath"; } } Folder Structure: projectName | ---> common | ---> pages | | | --->home | | | --->register | | | --->login | | | --->logout | | | --->page1 | | | --->page2 | | | --->page3 | ---> tpl | | | ---> common | --> home.php | --> register.php | --> login.php | --> logout.php | --> page1.php | --> page2.php | --> page3.php

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  • Generic version control strategy for select table data within a heavily normalized database

    - by leppie
    Hi Sorry for the long winded title, but the requirement/problem is rather specific. With reference to the following sample (but very simplified) structure (in psuedo SQL), I hope to explain it a bit better. TABLE StructureName { Id GUID PK, Name varchar(50) NOT NULL } TABLE Structure { Id GUID PK, ParentId GUID (FK to Structure), NameId GUID (FK to StructureName) NOT NULL } TABLE Something { Id GUID PK, RootStructureId GUID (FK to Structure) NOT NULL } As one can see, Structure is a simple tree structure (not worried about ordering of children for the problem). StructureName is a simplification of a translation system. Finally 'Something' is simply something referencing the tree's root structure. This is just one of many tables that need to be versioned, but this one serves as a good example for most cases. There is a requirement to version to any changes to the name and/or the tree 'layout' of the Structure table. Previous versions should always be available. There seems to be a few possibilities to tackle this issue, like copying the entire structure, but most approaches causes one to 'loose' referential integrity. Example if one followed this approach, one would have to make a duplicate of the 'Something' record, given that the root structure will be a new record, and have a new ID. Other avenues of possible solutions are looking into how Wiki's handle this or go a lot further and look how proper version control systems work. Currently, I feel a bit clueless how to proceed on this in a generic way. Any ideas will be greatly appreciated. Thanks leppie

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  • Storing users in a database

    - by EMcKenna
    Im wondering whats the best way of storing different types of users in my database. I am writing an application that has 4 main user types (admin, school, teacher, student). At the moment I have a table for each of these but i'm not sure thats the best way of storing user information. For instance... Allowing students to PM other student is simple (store sender and receiver student_id) but enabling teachers to PM students requires another table (sender teacher_id, sender student_id). Should all users be stored in one users table with a user_type field? If so, the teacher / student specific information will still have to be stored in another table. users user_id, password_hash, user_type students user_id, student_specific_stuff... teachers user_id, teacher_specific_stuff... How do I stop a user who has a user_type = student from being accidentally being entered into the teachers table (as both have a user_id) Just want to make sure I get the database correct before i go any further. Thanks...

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  • What performance overhead do IoC containers involve?

    - by Sosh
    Hi, Loose coupling is wonderful of course, but I have often wondered what overhead wiring up dynamically using an IoC container (for example Castle Windsor) has over a tightly coupled system? I know that a detailed answer would depend on what the IoC was being used for, but I'm really just trying to get a feel for the magnitude of effort involved in the IoC work. Does anyone have any stats or other resources regarding this? Thanks

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  • how to elegantly duplicate a graph (neural network)

    - by macias
    I have a graph (network) which consists of layers, which contains nodes (neurons). I would like to write a procedure to duplicate entire graph in most elegant way possible -- i.e. with minimal or no overhead added to the structure of the node or layer. Or yet in other words -- the procedure could be complex, but the complexity should not "leak" to structures. They should be no complex just because they are copyable. I wrote the code in C#, so far it looks like this: neuron has additional field -- copy_of which is pointer the the neuron which base copied from, this is my additional overhead neuron has parameterless method Clone() neuron has method Reconnect() -- which exchanges connection from "source" neuron (parameter) to "target" neuron (parameter) layer has parameterless method Clone() -- it simply call Clone() for all neurons network has parameterless method Clone() -- it calls Clone() for every layer and then it iterates over all neurons and creates mappings neuron=copy_of and then calls Reconnect to exchange all the "wiring" I hope my approach is clear. The question is -- is there more elegant method, I particularly don't like keeping extra pointer in neuron class just in case of being copied! I would like to gather the data in one point (network's Clone) and then dispose it completely (Clone method cannot have an argument though).

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  • Where are the new ideas in programming languages?

    - by 0xF
    I've recently been looking into the topic of programming languages and from what I've seen, few to none serious languages try making really "new" things that were not seen before their creation. Why do all more or less successful programming languages since 1980 or so just combine aspects of their predecessors? I just can't believe that programming languages "can't get any better"..

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