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  • How do You Get a Specific Value From a System.Data.DataTable Object?

    - by Giffyguy
    I'm a low-level algorithm programmer, and databases are not really my thing - so this'll be a n00b question if ever there was one. I'm running a simple SELECT query through our development team's DAO. The DAO returns a System.Data.DataTable object containing the results of the query. This is all working fine so far. The problem I have run into now: I need to pull a value out of one of the fields of the first row in the resulting DataTable - and I have no idea where to even start. Microsoft is so confusing about this! Arrrg! Any advice would be appreciated. I'm not providing any code samples, because I believe that context is unnecessary here. I'm assuming that all DataTable objects work the same way, no matter how you run your queries - and therefore any additional information would just make this more confusing for everyone.

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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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  • 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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  • Which MySQL Frontend shows foreign rows?

    - by Jeremy Rudd
    I once came across a MySQL Frontend app that displayed foreign linked rows within the parent row, if for instance the Events table has a foreign key to the Students table: Student ID Name DOB -- ---- --------- [+] 22 Bob 25-1-1984 [-] 21 Jane 25-1-1982 Event ID Student-ID Name Time -- ---------- ---- --------- 1 21 Event A 05:50 1 21 Event B 17:20 [+] 20 Jack 25-1-1980

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  • DbDataReader with DbTransactions

    - by Gustavo Paulillo
    Its the wrong way or lack of performance, using DbDataReader combinated with DbTransactions? An example of code: public DbDataReader ExecuteReader() { try { if (this._baseConnection.State == ConnectionState.Closed) this._baseConnection.Open(); if (this._baseCommand.Transaction != null) return this._baseCommand.ExecuteReader(); return this._baseCommand.ExecuteReader(CommandBehavior.CloseConnection); } catch (Exception excp) { if (this._baseCommand.Transaction != null) this._baseCommand.Transaction.Rollback(); this._baseCommand.CommandText = string.Empty; this._baseConnection.Close(); throw new Exception(excp.Message); } } Some methods call this operation. Sometimes openning a DbTransaction. Its using DbConnection and DbCommand. The real problem, is in production enviroment (like 5,000 access/day) the ADO operations start throwing exceptions

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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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  • mysql - select pagination chunk that includes a given id

    - by sean smith
    ...before the pagination chunks have been determined. I know you can do this in multiple statements, but there must be a better way. my results are returned ordered by date and I want to return the pagination chunk that contains a given id. So I could, for example, select the date of the given id and then select a chunk of results where date is less than or greater than the date. That would work. But is there some native mysql method of doing this sort of thing in one statement? It just seems reasonable to expect that we could ask for X results in which a given id exists if results are ordered by date.

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  • Why is Magento so slow?

    - by mr-euro
    Is Magento usually so terrible slow? This is my first experience with it and the admin panel simply takes ages to load and save changes. It is a default installation with the test data. The server it is hosted on serves other non-Magento sites super fast. What is it about the PHP code that Magento uses that makes it so slow, and what can be done to fix it?

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  • Using Active Objects and BLOBs

    - by Andrew L.
    I am in a group of people who are creating a Defect Tracking program as a project. We have been using Active Objects and have run into some issues. Currently maximum file size for the blob is approx. 2Mb but we want to be able to increase it up to 2Gb. We currently have been looking at many sites and have not been able to find out how to increase the size. We are currently storing the blob as an array of bytes. Our current error says, Packet for Query is too large? We don't know how to set the variable, and we don't know how to set it using AO. We are programming this in Java, too. We are wondering if anyone has a solution to this problem. Thanks for the Help.

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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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  • 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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  • 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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  • 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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  • Trapping errors in TClientDataSet.CommandText

    - by Rob McDonell
    I have a TClientDataSet connected to a TDataSetProvider, which in turn is connected to a TAdsTable. I set the SQL command and then open the ClientDataset something like this: try CDS.CommandText := 'SELECT * FROM tablename WHERE fieldname = 1'; CDS.Open except // trap exception here - this never gets executed! end; If the SQL statement in CommandText fails, however (syntax error or whatever) I get an exception within the Advantage code, but it never gets caught in my own exception handling code. Is there any way for me to trap this error and report it nicely to the user. Alternatively is there a way to verify the syntax of an SQL query before executing it? I'm using Delphi Pro 2009, and Advantage Local Server 9.

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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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  • Why isn't "String or Binary data would be truncated" a more descriptive error?

    - by rwmnau
    To start: I understand what this error means - I'm not attempting to resolve an instance of it. This error is notoriously difficult to troubleshoot, because if you get it inserting a million rows into a table 100 columns wide, there's virtually no way to determine what column of what row is causing the error - you have to modify your process to insert one row at a time, and then see which one fails. That's a pain, to put it mildly. Is there any reason that the error doesn't look more like this? String or Binary data would be truncated Error inserting value "Some 18 char value" into SomeTable.SomeColumn VARCHAR(10) That would make it a lot easier to find and correct the value, if not the table structure itself. If seeing the table data is a security concern, then maybe something generic, like giving the length of the attempted value and the name of the failing column?

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  • workbench vs phpmyadmin

    - by ajsie
    i've only used phpmyadmin but then i stumbled upon mysql workbench that looks promising. i wonder if someone has tried it out and could give your thoughts about it compared to phpmyadmin. could it replace phpmyadmin completely? 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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