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  • Has inheritance become bad?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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  • Dataset Binding stored procedures update/insert/delete

    - by Jin
    Hi all, I am currently having a problem since the DB has been changed. I am using Datasets for a c# application, and there is a user management system. For the security issues, our current DB design is like user log into app. DB returns a session ID On use of any other stored procedures, a session ID must be specified. BUT, the DB didn't request session ID before. since I am using the datasets, I used update/insert/delete stored procedures with "TableAdaptor Configuration Wizard". Bind Commands to Existing Stored Procedures (choose stored procedures to call and specify any reuiqred parameters) Now, it seems like I have to specify session ID for Insert/Update/Delete stored procedures. How do I specify session ID parameter here? It seems like I have to pick one return parameter variable from a select statement. Thanks,

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  • Beginner SQL question(s)

    - by unit
    I am two months in to an intro sql course, it's late at night, and I am drawing a blank. I have two tables, one customers, and one orders. I have to increase any customers credit limit by twenty five percent for all customers who have made two or more orders in which each order is more than the amount of 250.00. I get how to UPDATE CreditLimit * 1.25 and Cust with an order 250, but how the hell do I get it to check if they have made two orders over 250? Second question, we are just starting to take subqueries, and I am having a difficult time getting it into my skull. Another question posed by the prof of our class is to increase the credit limit of a customer who has an order that exceeds their credit limit. (Credit limit is on a customers table, order and amount are on an orders table). I then take that customer and UPDATE his CreditLimit +1000. Thanks for any help.

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  • What is the most efficient way to store and access images

    - by MT
    I am working on a project which has to store tens and thousands of images on a server and let the users access them. I need the most efficient method to store these images and to retrieve them. Also, I need information about which technology I should opt. I haven't started the project yet. So, I am thinking between PHP w/ CodeIgniter and Ruby on Rails. PS: The site is something similar to Flickr except that the images are uploaded only by the Authors of the content, and not by the users.

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  • How to properly design a simple favorites and blocked table?

    - by Nils Riedemann
    Hey, i am currently writing a webapp in rails where users can mark items as favorites and also block them. I came up two ways and wondered which one is more common/better way. 1. Separate join tables Would it be wise to have 2 tables for this? Like: users_favorites - user_id - item_id users_blocked - user_id - item_id 2. single table users_marks (or so) - users_id - item_id - type (["fav", "blk"]) Both ways seem to have advantages. Which one would you use and why?

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  • Multiple column foreign key contraints

    - by eugene4968
    I want to setup table constraints for the following scenario and I’m not sure how to do it or if it’s even possible in SQL Server 2005. I have three tables A,B,C. C is a child of B. B will have a optional foreign key(may be null) referencing A. For performance reasons I also want table C to have the same foreign key reference to table A. The constraint on table C should be that C must reference its parent (B) and also have the same foreign key reference to A as its parent. Anyone have any thoughts on how to do this?

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  • How to structure data... Sequential or Hierarchical?

    - by Ryan
    I'm going through the exercise of building a CMS that will organize a lot of the common documents that my employer generates each time we get a new sales order. Each new sales order gets a 5 digit number (12222,12223,122224, etc...) but internally we have applied a hierarchy to these numbers: + 121XX |--01 |--02 + 122XX |--22 |--23 |--24 In my table for sales orders, is it better to use the 5 digital number as an ID and populate up or would it be better to use the hierarchical structure that we use when referring to jobs in regular conversation? The only benefit to not populating sequentially seems to be formatting the data later on in my view, but that doesn't sound like a good enough reason to go through the extra work. Thanks

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  • Have 2 separate tables or an additional field in 1 table?

    - by hkansal
    Hello, I am making a small personal application regarding my trade of shares of various companies. The actions can be selling shares of a company or buying. Therefore, the details to be saved in both cases would be: Number of Shares Average Price Would it be better to use a separate tables for "buy" and "sell" or just use one table for "trade" and keep a field that demarcates "buy" from "sell"?

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  • Is this data set in third normal form?

    - by user2980802
    UNF: (Customer-name, Customer-id, Customer-address, (Unit-price, Order-id, Quantity, Product-id, Delivery-date) (Supplier-name, Supplier-id, Supplier-Address) 3NF: CUSTOMER (Customer-id, Order-id, Customer-name, Customer-address) ORDER (Order-id, Customer-id) ORDER/PRODUCT (Order-id, Quantity, Product-id) PRODUCT (Order-id, Product-id, Delivery-date, Supplier-id, Unit-price,) SUPPLIER (Supplier-name, Supplier-id, Supplier-Address, Product-id) Basically, the UNF is the un-normalised form. The information should have EXACTLY five tables, it's a hint we were given. The tables listed are the definite table names. We were told to make assumptions based on this information: Customer Invoice is generated from customer orders (Order & Order/Product entities) Supplier Order is generated for products that are low in stock (Product entity) Assumptions A customer can place many orders but an order is placed by only one customer An order can be for many products and a product can be ordered many times A product is supplied by only one supplier, a supplier may supply many products This is one of my modules in university and my lecturer is all but useful, I'm really struggling so any help is really appreciated.

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  • PHP - How to display other values, when a query is limited by 3?

    - by Dodi300
    Hello. Can anyone tell me how to display the other values, when a query is limited my 3. In this question I asked how to order and limit values, but now I want to show the others in another query. How would I go about doing this? Here's the code I used before: $query = "SELECT gmd FROM account ORDER BY gmd DESC LIMIT 3"; $result = mysql_query($query); while($row = mysql_fetch_array($result, MYSQL_ASSOC)) { } Thanks!

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  • Is inheritance bad nowadays?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

    Read the article

  • INSERT INTO ... SELECT ... vs dumping/loading a file in MySQL

    - by Daniel Huckstep
    What are the implications of using a INSERT INTO foo ... SELECT FROM bar JOIN baz ... style insert statement versus using the same SELECT statement to dump (bar, baz) to a file, and then insert into foo by loading the file? In my messing around, I haven't seen a huge difference. I would assume the former would use more memory, but the machine that this runs on has 8GB of RAM, and I never even see it go past half used. Are there any huge (or long term) performance implications that I'm not seeing? Advantages/disadvantages of either?

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  • Need recommendation for a table structure

    - by yapiskan
    I have an entity which has 4 different types of property that could have only one value for each case which are boolean, decimal, string or text. I don't want to define the table with 4 boolean, decimal, nvarchar and ntext columns. What would you recommend to cover this case?

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  • Regarding data storage in ecommerce applications

    - by geeth
    Why is MainFrame better choice to stores data related to customer, orders etc? I work with a online retail store, they use .net technologies for applications and MainFrames for storing product, customer, order etc related data. Is SQL DB server not a good option for these type of applications? How is MainFrames better choice than SQL DB? Please provide your insight.

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  • Changing javascript confirm dialog box to bootstrap

    - by Scape Goat
    I already this something Here is the original code: <script type='text/javascript'> function delete_user( id ){ var answer = confirm('Are you sure?'); //if user clicked ok if ( answer ){ //redirect to url with action as delete and id to the record to be deleted window.location = 'delete.php?id=' + id; } } </script> How do I remove the old javascript confirm dialog box and replace it with bootstrap?

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  • Using C# to read/write from excel spreadsheet.

    - by Aaron
    Hi there, I need to make a program that writes some data to an excel spreadsheet. Something basic along the lines of First name, last name, phone number, e-mail per row with each category in its own column. I don't even know where to start. If someone could tell me which assemblies to reference and maybe point me to a website or a book that covers writing/reading data from an excel spreadsheet via a c# program that would be great. Many thanks.

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  • NoSQL vs Relational Coding Styles

    - by Chris Henry
    When building objects that make use of data stored in a RDBMS, it's normally pretty clear what you're getting back, as dictated by the tables and columns being queried. However, when dealing with NoSQL, document-based systems, it's less clear what is being retrieved. What are common methods of keeping track of structure in which data is stored?

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