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  • Historical / auditable database

    - by Mark
    Hi all, This question is related to the schema that can be found in one of my other questions here. Basically in my database I store users, locations, sensors amongst other things. All of these things are editable in the system by users, and deletable. However - when an item is edited or deleted I need to store the old data; I need to be able to see what the data was before the change. There are also non-editable items in the database, such as "readings". They are more of a log really. Readings are logged against sensors, because its the reading for a particular sensor. If I generate a report of readings, I need to be able to see what the attributes for a location or sensor was at the time of the reading. Basically I should be able to reconstruct the data for any point in time. Now, I've done this before and got it working well by adding the following columns to each editable table: valid_from valid_to edited_by If valid_to = 9999-12-31 23:59:59 then that's the current record. If valid_to equals valid_from, then the record is deleted. However, I was never happy with the triggers I needed to use to enforce foreign key consistency. I can possibly avoid triggers by using the extension to the "PostgreSQL" database. This provides a column type called "period" which allows you to store a period of time between two dates, and then allows you to do CHECK constraints to prevent overlapping periods. That might be an answer. I am wondering though if there is another way. I've seen people mention using special historical tables, but I don't really like the thought of maintainling 2 tables for almost every 1 table (though it still might be a possibility). Maybe I could cut down my initial implementation to not bother checking the consistency of records that aren't "current" - i.e. only bother to check constraints on records where the valid_to is 9999-12-31 23:59:59. Afterall, the people who use historical tables do not seem to have constraint checks on those tables (for the same reason, you'd need triggers). Does anyone have any thoughts about this? PS - the title also mentions auditable database. In the previous system I mentioned, there is always the edited_by field. This allowed all changes to be tracked so we could always see who changed a record. Not sure how much difference that might make. Thanks.

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  • Invoicing vs Quoting

    - 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. 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?

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  • How to create a "facade" table?

    - by tputkonen
    A legacy database contains a join table which links tables table1 and table2, and contains just two foreign keys: TABLE_ORIG: table1_id table2_id In order to utilize this table using JPA I would need to create a surrogate primary key to the link table. However, the existing table must not be modified at all. I would like to create another table which would contain also a primary key in addition to the foreign keys: TABLE_NEW: id table1_id table2_id All changes to TABLE_ORIG should be reflected in TABLE_NEW, and vice versa. Is this doable in mysql?

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  • Struggling with a data modeling problem

    - by rpat
    I am struggling with a data model (I use MySQL for the database). I am uneasy about what I have come up with. If someone could suggest a better approach, or point me to some reference matter I would appreciate it. The data would have organizations of many types. I am trying to do a 3 level classification (Class, Category, Type). Say if I have 'Italian Restaurant', it will have the following classification Food Services Restaurants Italian However, an organization may belong to multiple groups. A restaurant may also serve Chinese and Italian. So it will fit into 2 classifications Food Services Restaurants Italian Food Services Restaurants Chinese The classification reference tables would be like the following: ORG_CLASS (RowId, ClassCode, ClassName) 1, FOOD, Food Services ORG_CATEGORY(RowId, ClassCode, CategoryCode, CategoryName) 1, FOOD, REST, Restaurants ORG_TYPE (RowId, ClassCode, CategoryCode, TypeCode, TypeName) 100, FOOD, REST, ITAL, Italian 101, FOOD, REST, CHIN, Chinese 102, FOOD, REST, SPAN, Spanish 103, FOOD, REST, MEXI, Mexican 104, FOOD, REST, FREN, French 105, FOOD, REST, MIDL, Middle Eastern The actual data tables would be like the following: I will allow an organization a max of 3 classifications. I will have 3 GroupIds each pointing to a row in ORG_TYPE. So I have my ORGANIZATION_TABLE ORGANIZATION_TABLE (OrgGroupId1, OrgGroupId2, OrgGroupId3, OrgName, OrgAddres) 100,103,NULL,MyRestaurant1, MyAddr1 100,102,NULL,MyRestaurant2, MyAddr2 100,104,105, MyRestaurant3, MyAddr3 During data add, a dialog could let the user choose the clssa, category, type and the corresponding GroupId could be populated with the rowid from the ORG_TYPE table. During Search, If all three classification are chosen, It will be more specific. For example, if Food Services Restaurants Italian is the criteria, the where clause would be 'where OrgGroupId1 = 100' If only 2 levels are chosen Food Services Restaurants I have to do 'where OrgGroupId1 in (100,101,102,103,104,105, .....)' - There could be a hundred in that list I will disallow class level search. That is I will force selection of a class and category The Ids would be integers. I am trying to see performance issues and other issues. Overall, would this work? or I need to throw this out and start from scratch.

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  • Using OpenGL drawing operations in an object-oriented setting?

    - by Lion Kabob
    I've been plowing through basic shaders and whatnot for an application I'm writing, and I've been having trouble figuring out a high-level organization for the drawing calls. I'm thinking of having a singleton class which implements a number of basic drawing operations, taking data from "user" classes and passing that to the appropriate opengl calls. I'm wondering how people do this when writing their own applications, as the internet is chock full of basic "Your first shader" tutorials, but very little on suggested organization of drawing code. My particular environment is targeted at iPad/OpenGL ES 2.0, but I think the question stands for most environments.

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  • In .NET, Why Can I Access Private Members of a Class Instance within the Class?

    - by AMissico
    While cleaning some code today written by someone else, I changed the access modifier from Public to Private on a class variable/member/field. I expected a long list of compiler errors that I use to "refactor/rework/review" the code that used this variable. Imagine my surprise when I didn't get any errors. After reviewing, it turns out that another instance of the Class can access the private members of another instance declared within the Class. Totally unexcepted. Is this normal? I been coding in .NET since the beginning and never ran into this issue, nor read about it. I may have stumbled onto it before, but only "vaguely noticed" and move on. Can anyone explain this behavoir to me? I would like to know the "why" I can do this. Please explain, don't just tell me the rule. Am I doing something wrong? I found this behavior in both C# and VB.NET. The code seems to take advantage of the ability to access private variables. Sincerely, Totally Confused Class Jack Private _int As Integer End Class Class Foo Public Property Value() As Integer Get Return _int End Get Set(ByVal value As Integer) _int = value * 2 End Set End Property Private _int As Integer Private _foo As Foo Private _jack As Jack Private _fred As Fred Public Sub SetPrivate() _foo = New Foo _foo.Value = 4 'what you would expect to do because _int is private _foo._int = 3 'TOTALLY UNEXPECTED _jack = New Jack '_jack._int = 3 'expected compile error _fred = New Fred '_fred._int = 3 'expected compile error End Sub Private Class Fred Private _int As Integer End Class End Class

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  • Efficient algorithm for creating an ideal distribution of groups into containers?

    - by Inshim
    I have groups of students that need to be allocated into classrooms of a fixed capacity (say, 100 chairs in each). Each group must only be allocated to a single classroom, even if it is larger than the capacity (ie there can be an overflow, with students standing up) I need an algorithm to make the allocations with minimum overflows and under-capacity classrooms. A naive algorithm to do this allocation is horrendously slow when having ~200 groups, with a distribution of about half of them being under 20% of the classroom size. Any ideas where I can find at least some good starting point for making this algorithm lightning fast? Thanks!

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  • CSS for top right corner of the page

    - by user102533
    How would I have a top right corner div as shown in the image. I want to do something similar though not exactly the same. I think the text is not an image. Also, I have seen some websites that has a page hover effect when a mouse is over the top right section. Any idea how to do that?

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  • How do i make my text wrap in a <div> with a large border radius

    - by Greg Guida
    in the following code <html> <body> <div style="height:400px; width:400px; -moz-border-radius:100px; -webkit-border-radius:100px; border:3px solid #500; background-color:#a00; overflow:hidden;"> Why is this getting cut at the beginning??? </div> </body> </html> Why isn't the browser wrapping the text around the rounded corners. In webkit browsers(i tested both chrome and safari) the overflow hidden cuts the text outside the border. Firefox just renders text outside the border. I also tried this without overflow:hidden; but again the text just rendered outside the border.

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  • Best XML Based Database

    - by monmonja
    I had been assigned to develop a system on where we would get a XML from multiple sources (millions of xml) and put them in some database like and judging from the xml i would receive, there wont be any concrete structure even if they are from the same source. With this reason i think i cannot suggest RDMS and currently looking at NoSQL databases. We need a system that could do CRUD and is fast on Read. I had been looking at MarkLogic and eXist, which are both XML based NoSQL databases, have anyone had experience with them? and any other suggestion? Thanks

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  • Using implicit conversion as a substitute for multiple inheritance in .NET

    - by Daniel Plaisted
    I have a situation where I would like to have objects of a certain type be able to be used as two different types. If one of the "base" types was an interface this wouldn't be an issue, but in my case it is preferable that they both be concrete types. I am considering adding copies of the methods and properties of one of the base types to the derived type, and adding an implicit conversion from the derived type to that base type. Then users will be able treat the derived type as the base type by using the duplicated methods directly, by assigning it to a variable of the base type, or by passing it to a method that takes the base type. It seems like this solution will fit my needs well, but am I missing anything? Is there a situation where this won't work, or where it is likely to add confusion instead of simplicity when using the API?

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  • Are there any online database schema drawing tools?

    - by Pure.Krome
    Hi folks, i wish to draw up some database schemas. Eg, table 1 has zero to many rows in table 2, etc. It's purely for visual purposes (eg. no sql code, etc). Are there any online tools / website that offer this? (please don't say: Use Sql Server Database Diagrams, print screen, upload to image hosting service). thanks :) EDIT: Please take note of the keyword - ONLINE. I don't want any desktop solutions (because I already have one of these).

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  • How to maintain an ordered table with Core Data (or SQL) with insertions/deletions?

    - by Jean-Denis Muys
    This question is in the context of Core Data, but if I am not mistaken, it applies equally well to a more general SQL case. I want to maintain an ordered table using Core Data, with the possibility for the user to: reorder rows insert new lines anywhere delete any existing line What's the best data model to do that? I can see two ways: 1) Model it as an array: I add an int position property to my entity 2) Model it as a linked list: I add two one-to-one relations, next and previous from my entity to itself 1) makes it easy to sort, but painful to insert or delete as you then have to update the position of all objects that come after 2) makes it easy to insert or delete, but very difficult to sort. In fact, I don't think I know how to express a Sort Descriptor (SQL ORDER BY clause) for that case. Now I can imagine a variation on 1): 3) add an int ordering property to the entity, but instead of having it count one-by-one, have it count 100 by 100 (for example). Then inserting is as simple as finding any number between the ordering of the previous and next existing objects. The expensive renumbering only has to occur when the 100 holes have been filled. Making that property a float rather than an int makes it even better: it's almost always possible to find a new float midway between two floats. Am I on the right track with solution 3), or is there something smarter?

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  • Is it immoral to write crappy code even if readability and correctness is not a requirement?

    - by mafutrct
    There are cases when crappy (i.e. unreadable and buggy) code is not much of a problem. For instance, imagine you need to generate a big text file that mostly follows a simple pattern with a few very complex exceptions. What do you do? You quickly write a simple algorithm and insert the exceptional bits in the output manually to save 4 hours. The code is unreadable, and the output is flawed, but it's still the correct way since it is way faster. But let's get this straight: I hate bad code. I've had to read and work with code that caused my stomach to hurt. I care a lot about good code. And actually, I caught myself thinking that it is immoral to write bad code even though the dirty approach is sometimes superior. I was surprised by myself and found my idea to be very irrational. Did you ever experience this? Should I just get rid of this stupid idea and use the most efficient approach to coding?

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  • Performance Tricks for C# Logging

    - by Charles
    I am looking into C# logging and I do not want my log messages to spend any time processing if the message is below the logging threshold. The best I can see log4net does is a threshold check AFTER evaluating the log parameters. Example: _logger.Debug( "My complicated log message " + thisFunctionTakesALongTime() + " will take a long time" ) Even if the threshold is above Debug, thisFunctionTakesALongTime will still be evaluated. In log4net you are supposed to use _logger.isDebugEnabled so you end up with if( _logger.isDebugEnabled ) _logger.Debug( "Much faster" ) I want to know if there is a better solution for .net logging that does not involve a check each time I want to log. In C++ I am allowed to do LOG_DEBUG( "My complicated log message " + thisFunctionTakesALongTime() + " will take no time" ) since my LOG_DEBUG macro does the log level check itself. This frees me to have a 1 line log message throughout my app which I greatly prefer. Anyone know of a way to replicate this behavior in C#?

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  • Anything similar to Hibernate in PHP?

    - by harigm
    I am a Java programmer and was working on a project using Hibernate and Struts for some time. Now For my new project, I am working on PHP and Mysql (learning PHP). Is there any technology which is similar to Hibernate for PHP? If yes, can anyone give me the link where I can understand and use it? Is there a POJO concept in PHP?

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  • Computation geometry: find where's the triangle after rotation, tranlastion or reflection in a mirro

    - by newba
    Hi, I have a small contest problem in which is given a set of points, in 2D, that form a triangle. This triangle may be subject to an arbitrary rotation, may be subject to an arbitrary translation (both in the 2D plane) and may be subject to a reflection on a mirror, but its dimensions were kept unchanged. Then, they give me a set of points in the plane, and I have to find 3 points that form my triangle after one or more of those geometric operations. Example: 5 15 8 5 20 10 6 5 17 5 20 20 5 10 5 15 20 15 10 I bet that have to apply some known algorithm, but I don't know which. The most common are: convex hull, sweep plane, triangulation, etc. Can someone give a tip? I don't need the code, only a push, please!

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  • How to fluent-map this (using fluent nhibernate)?

    - by vikasde
    I have two tables in my database "Styles" and "BannedStyles". They have a reference via the ItemNo. Now styles can be banned per store. So if style x is banned at store Y then its very possible that its not banned at store Z or vice verse. What is the best way now to map this to a single entity? Should I be mapping this to a single entity? My Style entity looks like this: public class Style { public virtual int ItemNo { get; set;} public virtual string SKU { get; set; } public virtual string StyleName { get; set; } public virtual string Description { get; set; } public virtual Store Store { get; set; } public virtual bool IsEntireStyleBanned { get; set; } }

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  • Graph-structured databases and Php

    - by stagas
    I want to use a graph database using php. Can you point out some resources on where to get started? Is there any example code / tutorial out there? Or are there any other methods of storing data that relate to each other in totally random/abstract situations? - Very abstract example of the relations needed: John relates to Mary, both relate to School, John is Tall, Mary is Short, John has Blue Eyes, Mary has Green Eyes, query I want is which people are related to 'Short people that have Green Eyes and go to School' - answer John - Another example: TrackA -> ArtistA -> ArtistB -> AlbumA -----> [ label ] -> AlbumB -----> [ A ] -> TrackA:Remix -> Genre:House -> [ Album ] -----> [ label ] TrackB -> [ C ] [ B ] Example queries: Which Genre is TrackB closer to? answer: House - because it's related to Album C, which is related to TrackA and is related to Genre:House Get all Genre:House related albums of Label A : result: AlbumA, AlbumB - because they both have TrackA which is related to Genre:House - It is possible in MySQL but it would require a fixed set of attributes/columns for each item and a complex non-flexible query, instead I need every attribute to be an item by itself and instead of 'belonging' to something, to be 'related' to something.

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  • How do I indicate success and failure with colour?

    - by Steve McLeod
    I need to make a Java component that turns the background a certain colour when a process passed, and another colour when the process failed. My first thought was: green for success, red for failure. But then I read that 10% of males can't differentiate between these two colours. What would be a better combination of colours? (For the nitpickers: yes, I know that colour alone doesn't suffice, that text, shape, and noise can also be used. Nevertheless I am asking about the appropriate use of colour.)

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  • Are there old versions of Windows UX guidelines somewhere?

    - by Camilo Martin
    Since I've read Windows User Experience Interaction Guidelines (there's a PDF download avaliable) I've found it to be admirably self-deprecating, humbly pointing out their own horrible UI practices long scolded by Joel Spolsky. I'd like to know, however, what they had in mind while they made those mistakes. Is this (terrific) UX Guidelines document something new, or were there previous issues of such? If so, where can I find them? My prayers to Google yielded no leniency.

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