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  • Can someone describe the nested set model from a C#/LINQ perspective?

    - by Chad
    I know the nested set model doesn't pertain to the C# language or LINQ directly... it's what I'm using to develop my web app. For hierarchical data (categories with sub-categories in my case), I'm currently using something similar to the Adjacency List model. At the moment, I've only got 2 levels of categories, but I'd like to take it further and allow for n levels of categories using the nested set model. I'm not quite clear on how to use it in a C# context. Here's the article I'm reading on the nested set model. Though this article cleared up my confusion some, I still have a big ?? in my head: - Is inserting, updating or deleting categories tedious? It looks like the left and right numbers would require re-numbering... what would the LINQ queries look like for the following scenarios? Delete a child node (re-number all node's left/right values) Delete a parent node (what do you do with the orphans?) Move a child node to a different parent node (renumber again) If my understanding is correct, at all times the child node's left/right values will always be between the parent node's left/right values, am I correct? Seems easy enough, if only the categories were static... most likely I need to spend more time to get my head around the concept. Any help is greatly appreciated!

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  • Algorithms for finding a numerical record in a list of ordered numbers

    - by Ankur
    I have a list of incomplete ordered numbers. I want to find a particular number with as few steps as possible. Are there any improvements on this algorithm, I assume you can count the set size without difficulty - it will be stored and updated every time a new item is added. Your object is to get your cursor over the value x The first number (smallest) is s, and the last number (greatest) is g. Take the midpoint m1 of the set: calculate is x < m1, If yes then s <= x < m1 If no then m1 < x <= g If m1 = x then you're done. Keep repeating till you find x. Basically dividing the set into two parts with each iteration till you hit x. The purpose is to retrieve a numerical id from a very large table to then find the associated other records. I would imagine this is the most trivial kind of indexing available, are there improvements?

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  • SQL Server: A Grouping question that's annoying me

    - by user366729
    I've been working with SQL Server for the better part of a decade, and this grouping (or partitioning, or ranking...I'm not sure what the answer is!) one has me stumped. Feels like it should be an easy one, too. I'll generalize my problem: Let's say I have 3 employees (don't worry about them quitting or anything...there's always 3), and I keep up with how I distribute their salaries on a monthly basis. Month Employee PercentOfTotal -------------------------------- 1 Alice 25% 1 Barbara 65% 1 Claire 10% 2 Alice 25% 2 Barbara 50% 2 Claire 25% 3 Alice 25% 3 Barbara 65% 3 Claire 10% As you can see, I've paid them the same percent in Months 1 and 3, but in Month 2, I've given Alice the same 25%, but Barbara got 50% and Claire got 25%. What I want to know is all the distinct distributions I've ever given. In this case there would be two -- one for months 1 and 3, and one for month 2. I'd expect the results to look something like this (NOTE: the ID, or sequencer, or whatever, doesn't matter) ID Employee PercentOfTotal -------------------------------- X Alice 25% X Barbara 65% X Claire 10% Y Alice 25% Y Barbara 50% Y Claire 25% Seems easy, right? I'm stumped! Anyone have an elegant solution? I just put together this solution while writing this question, which seems to work, but I'm wondering if there's a better way. Or maybe a different way from which I'll learn something. WITH temp_ids (Month) AS ( SELECT DISTINCT MIN(Month) FROM employees_paid GROUP BY PercentOfTotal ) SELECT EMP.Month, EMP.Employee, EMP.PercentOfTotal FROM employees_paid EMP JOIN temp_ids IDS ON EMP.Month = IDS.Month GROUP BY EMP.Month, EMP.Employee, EMP.PercentOfTotal Thanks y'all! -Ricky

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  • archiving table records to another table by trigger(move daialy table records to weekly table, evry

    - by sirvan
    I have written this trigger in mysql 5: create trigger changeToWeeklly after insert on tbl_daily for each row begin insert into tbl_weeklly SELECT * FROM vehicleslocation v where v.recivedate < curdate(); delete FROM tbl_daily where recivedate < curdate(); end; i want to archive records by date, move yesterday inserted record from dailly to weekly table and last weekly table to mounthly table and deletes this records from previous table this trigger has following error when insert in daily tabled occurred : "Can't update table 'tbl_daily' in stored function/trigger because it is already used by statement which invoked this stored function/trigger." please help me to solve th problem of archive old data in related tables: move yesterday inserted records to weekly table, if there is a reliable solution tell me please.

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  • Inserting Rows in Relationship using a Strongly Typed DataSet

    - by Manuel Faux
    I'm using ADO.NET with a strongly typed dataset in C# (.NET 3.5). I want to insert a new row to two tables which are related in an 1:n relation. The table Attachments holds the primary key part of the relation and the table LicenseAttachments holds the foreign key part. AttachmentsDataSet.InvoiceRow invoice; // Set to a valid row, also referenced in InvoiceAttachments AttachmentsDataSet.AttachmentsRow attachment; attachment = attachmentsDataSet.Attachments.AddAttachmentsRow("Name", "Description"); attachmentsDataSet.InvoiceAttachments.AddInvoiceAttachmentsRow(invoice, attachment); Of course when I first update the InvoicesAttachments table, I'll get a foreign key violation from the SQL server, so I tried updating the Attachments table first, which will create the rows, but will remove the attachment association in the InvoiceAttachments table. Why? How do I solve this problem?

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  • SQL to retrieve the latest records, grouping by unique foreign keys

    - by jbox
    I'm creating query to retrieve the latest posts in a forum using a SQL DB. I've got a table called "Post". Each post has a foreign key relation to a "Thread" and a "User" as well as a creation date. The trick is I don't want to show two posts by the same user or two posts in the same thread. Is it possible to create a query that contains all this logic? # Grab the last 10 posts. SELECT id, user_id, thread_id FROM posts ORDER BY created_at DESC LIMIT 10; # Grab the last 10 posts, max one post per user SELECT id, user_id, thread_id FROM post GROUP BY user_id ORDER BY date DESC LIMIT 10; # Grab the last 10 posts, max one post per user, max one post per thread???

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  • Problem performance datawarehouse with lots of indexes

    - by Lieven Cardoen
    Our product takes tests of some 350 candidates at the same time. At the end of the test, results for each candidate are moved to a datawarehouse full of indexes on it. For each test there's some 400 records to be entered in datawarehouse. So 400 x 350 is a lot of records. If there are not much records in the datawarehouse, all goes well. But if there are already lots of records in the datawarehouse, then a lot of inserts fail... Is there a way to have indexes that are only rebuild at the end of the day or isn't that the real problem? Or how would you solve this?

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  • B- trees, B+ trees difference

    - by dta
    In a B- tree you can store both keys and data in the internal/leaf nodes. But in a B+ tree you have to store the data in the leaf nodes only. Is there any advantage of doing the above in a B+ tree? Why not use B- trees instead of B+ trees everywhere? As intuitively they seem much faster. I mean why do you need to replicate the key(data) in a B+ tree?

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  • FileFinder using SQL

    - by James Morgan
    I was thinking of working on a project while I have some free time and this one looks pretty nice: http://mindprod.com/project/filefinder.html One thing I'm wondering about is that will it really be much faster compared to the regular windows search if I use SQL? I'm planning to use MySQL since it's open source. Also, do I need to be good at databases for this? I have basic knowledge about relational databases and can definitely make some SQL statements. Thanks.

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  • Empty data problem - data layer or DAL?

    - by luckyluke
    I designing the new App now and giving the following question a lot of thought. I consume a lot of data from the warehouse, and the entities have a lot of dictionary based values (currency, country, tax-whatever data) - dimensions. I cannot be assured though that there won't be nulls. So I am thinking: create an empty value in each of teh dictionaries with special keyID - ie. -1 do the ETL (ssis) do the correct stuff and insert -1 where it needs to let the DAL know that -1 is special (Static const whatever thing) don't care in the code to check for nullness of dictionary entries because THEY will always have a value But maybe I should be thinking: import data AS IS let the DAL do the thinking using empty record Pattern still don't care in the code because business layer will have what it needs from DAL. I think is more of a approach thing but maybe i am missing something important here... What do You think? Am i clear? Please don't confuse it with empty record problem. I do use emptyCustomer think all the time and other defaults too.

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  • Datamapper, defining your own object methods, how?

    - by Dublinclontarf
    So lets say I have a class like below class List include DataMapper::Resource property :id, Serial property :username, String def self.my_username return self[:username] end end list=List.create(:username=>,'jim') list.my_username When I run this it tells me that the method cannot be found, and on more investigation that you can only define class methods(not object methods) and that class methods don't have access to objects data. Is there any way to have these methods included as object methods and get access to object data? I'm using Ruby 1.8.6 and the latest version of datamapper.

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  • is it possible to have an sqlite database in a sqlserver field?

    - by Behrooz
    I think my question seems to be vague. I am trying to save user settings in SQLServer, but the problem can be expressed in this term:"it needs 20 tables with circular dependencies. and i have enough tables to fill 3 database diagrams", so the best way encountered to my brain is to save it as a sqlite database in a field, like this: Index |Name |Data 1 |Behrooz |*sqlite database here* 2 |User1 |*sqlite database here* ... is this way the right way?is it stupid? should i create more tables instead of doing all these? does it increase database fragmention?

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  • Re-using aggregate level formulas in SQL - any good tactics?

    - by Cade Roux
    Imagine this case, but with a lot more component buckets and a lot more intermediates and outputs. Many of the intermediates are calculated at the detail level, but a few things are calculated at the aggregate level: DECLARE @Profitability AS TABLE ( Cust INT NOT NULL ,Category VARCHAR(10) NOT NULL ,Income DECIMAL(10, 2) NOT NULL ,Expense DECIMAL(10, 2) NOT NULL ) ; INSERT INTO @Profitability VALUES ( 1, 'Software', 100, 50 ) ; INSERT INTO @Profitability VALUES ( 2, 'Software', 100, 20 ) ; INSERT INTO @Profitability VALUES ( 3, 'Software', 100, 60 ) ; INSERT INTO @Profitability VALUES ( 4, 'Software', 500, 400 ) ; INSERT INTO @Profitability VALUES ( 5, 'Hardware', 1000, 550 ) ; INSERT INTO @Profitability VALUES ( 6, 'Hardware', 1000, 250 ) ; INSERT INTO @Profitability VALUES ( 7, 'Hardware', 1000, 700 ) ; INSERT INTO @Profitability VALUES ( 8, 'Hardware', 5000, 4500 ) ; SELECT Cust ,Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability GROUP BY Cust SELECT Category ,Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability GROUP BY Category SELECT Profit = SUM(Income - Expense) ,Margin = SUM(Income - Expense) / SUM(Income) FROM @Profitability Notice how the same formulae have to be used at the different aggregation levels. This results in code duplication. I have thought of using UDFs (either scalar or table valued with an OUTER APPLY, since many of the final results may share intermediates which have to be calculated at the aggregate level), but in my experience the scalar and multi-statement table-valued UDFs perform very poorly. Also thought about using more dynamic SQL and applying the formulas by name, basically. Any other tricks, techniques or tactics to keeping these kinds of formulae which need to be applied at different levels in sync and/or organized?

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  • Pervasive SQL german Umlauts Problem

    - by cordellcp3
    Hi there, I'm using the Pervasive SQL - ADO.NET 3.5 DataProvider for retrieving data out of the PSQL DB and I've noticed that the german umlauts (äöüÄÖÜ etc.) are not represented correctly in the PSQLDataReader, but in the Pervasive Control Center (similar to the sql management studio) the umlauts are all correct. Is there anything similar to the TSQL "SET LANGUAGE"-command? I havn't found something like that for Pervasive SQL. Googling this issue wasn't successful at all, too. Although I did find some tips with a file called upper.alt or collate.cfg, but don't know how to use this files and I coudn`t find them in my installation. (I'm totally new to Pervasive...) I hope that someone on here could help me with that. Thanks in advance

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  • Light-weight client/server DB?

    - by OverTheRainbow
    Hello, (This question falls between programming and finding a tool, so I guess I'll ask here in SO since it has more activity than SuperUser.) I like the simplicity of SQLite, but by design, it doesn't support concurrent access. The apps I write don't have heavy needs, so I'd like to avoid heavier solutions like MySQL that are more difficult to deploy (remote customers with usually no computer personnel). Does someone know of a good solution that would offer the following features? Client available for VB.Net applications The server itself doesn't have to be a .Net application. Actually, I'd rather a bare-metal server so that it can run even on embedded Linux hosts with less RAM/CPU than regular PC's Easy install: the client part should either be statically linked inside the client application or be available as a single DLL, and the server should just be a single EXE listening for queries, à la Fossil (http://www.fossil-scm.org) clients can locate the server on the LAN by broadcasting data picked up by the server, so users don't have to write down the IP address and paste it into each client open-source, or moderately priced closed-source Thank you.

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  • Searching 2 fields at the same time

    - by donpal
    I have a table of first and last names firstname lastname --------- --------- Joe Robertson Sally Robert Jim Green Sandra Jordan I'm trying to search this table based on an input that consists of the full name. For example: input: Joe Robert I thought about using SELECT * FROM tablename WHERE firstname LIKE BUT the table stores the first and last name separately, so I'm not sure how to do the search in this case

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  • Best ORM, Simple data Structures, Strong Query analysis.

    - by sayth
    What is the best ORM db combination for simple data structures. That is data that contains names as identifiers and locations, but whose main interaction will be numerical data for times(sports durations), and currency related data. I initially want to create a sports data base that will take names and statistics. Secondarily I plan to start into an investment and stock analysis db. Which ORM suits storing many numerical types and have strong query functions? I really am not biased to db engine (most likely use sqlite or mongo) so any suggestions to best network less db server to suit said ORM appreciated.

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  • When NOT to use Cassandra?

    - by JimJim
    There has been a lot of talk related to Cassandra lately. Twitter, Digg, Facebook, etc all use it. When does it make sense to: use Cassandra, not use Cassandra, and use a RDMS instead of Cassandra.

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