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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • HOWTO - Compare a date string to datetime in SQL Server?

    - by Guy
    In SQL Server I have a DATETIME column which includes a time element. Example: '14 AUG 2008 14:23:019' What is the best method to only select the records for a particular day, ignoring the time part? Example: (Not safe, as it does not match the time part and returns no rows) DECLARE @p_date DATETIME SET @p_date = CONVERT( DATETIME, '14 AUG 2008', 106 ) SELECT * FROM table1 WHERE column_datetime = @p_date Note: Given this site is also about jotting down notes and techniques you pick up and then forget, I'm going to post my own answer to this question as DATETIME stuff in MSSQL is probably the topic I lookup most in SQLBOL. Update Clarified example to be more specific. Edit Sorry, But I've had to down-mod WRONG answers (answers that return wrong results). @Jorrit: WHERE (date>'20080813' AND date<'20080815') will return the 13th and the 14th. @wearejimbo: Close, but no cigar! badge awarded to you. You missed out records written at 14/08/2008 23:59:001 to 23:59:999 (i.e. Less than 1 second before midnight.)

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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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  • 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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  • 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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  • Importing json data into MySQL?

    - by AP257
    Pretty much what the title says :) At the moment I'm using Python to turn the json data into a plain-text tab-separated file, and then mysqlimport to pull that into my MySQL tables. Anyone know a nicer / more direct way?

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  • Move million records from MEMORY table to MYISAM table.

    - by Prashant
    Hi, I am looking for a fast way to move records from a MEMORY table to MYISAM table. MEMORY table has around 0.5 million records. Both tables have exactly the same structure (same number of columns, data types etc.). But the MYISAM table is indexed (B-TREE) on a few columns. There are around 25 columns most of which are unsigned integers. I have already tried using "INSERT INTO SELECT * FROM " query. But is there any faster way to do this? Appreciate your help. Prashant

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  • how to effectively modify index

    - by daedlus
    Hej everyone, problem : I am looking for right way to convert an index from clustered to non-clustered Description : I have a table as below in sybase db: dbo.UserLog Id | UserId |time | .... This is hash partitioned using UserId. Currently it has 2 indexes UserId : non-clustered time: clustered This table has about 20 million records. I now want to make UserId as clustered index and time as non-clustered index. is it correct to user alter index to change from clustered to non-clustered or do i drop index and recreate. does the fact that userId is used in hash partitioning have any implications to this? To me alter seems way to go but I have not yet tried this.

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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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  • 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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  • Versioned RDF store

    - by Mat
    Let me try rephrasing this: I am looking for a robust RDF store or library with the following features: Named graphs, or some other form of reification. Version tracking (probably at the named graph level). Privacy between groups of users, either at named graph or triple level. Human-readable data input and output, e.g. TriG parser and serialiser. I've played with Jena, Sesame, Boca, RDFLib, Redland and one or two others some time ago but each had its problems. Have any improved in the above areas recently? Can anything else do what I want, or is RDF not yet ready for prime-time? Reading around the subject a bit more, I've found that: Jena, nothing further Sesame, nothing further Boca does not appear to be maintained any more and seems only really designed for DB2. OpenAnzo, an open-source fork, appears more promising. RDFLib, nothing further Redland, nothing further Talis Platform appears to support changesets (wiki page and reference in Kniblet Tutorial Part 5) but it's a hosted-only service. Still may look into it though. SemVersion sounded promising, but appears to be stale.

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  • adding one time options to items

    - by rap-uvic
    Hello, I'm building an Event Registration site. For any given event, we'll have a handful of items to choose from. I have a table for these items. For each event we might have special options for users. For example, for one of the events new users get to buy an item which is not available to other users. This may not apply to all the events. For other events we might have some other restriction on items. I will obviously be checking this programmatically on application side. I would like to though, set up a column containing flag in the items table. But I don't find it feasible because this condition may only apply to one particular event. I don't want all the future items to have this column. What is a good approach to take in such a situation? Should I create a special "restrictions" table and just do a join? How would I handle this on the application side?

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