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  • Help Me With This MS-Access Query

    - by yae
    I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are related with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. "Products" table contains all products (p EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obtain the price of the main product, but not runs. This query not returns any value: SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5)); MORE INFO The table "products" contains all the products to sell that it is in the shop. The table "pieces" is to take a control of the compound products. To know those who are the products children. For example of compound product: computers. This product is composed by other products (motherboard, hard disk, memory, cpu, etc.)

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  • Tool or library for end-users to run queries to select (not modify) data?

    - by Mark Rushakoff
    For a utility I'm working on, the client would like to be able to generate graphic reports on the data that has been collected. I can already generate a couple canned graphs (using ZedGraph, which is a very nice library); however, the utility would be much more flexible if the graphs were more programmable or configurable by the end-user. TLDR version I want users to be able to use something like SQL to safely extract and select data from a List of objects that I provide and can describe. What free tools or libraries will help me accomplish this? Full version I've given thought to using IronPython, IronRuby, and LuaInterface, but frankly they're all a bit overpowered for what I want to do. My classes are fairly simple, along the lines of: class Person: string Name; int HeightInCm; DateTime BirthDate; Weight[] WeighIns; class Weight: int WeightInKg; DateTime Date; Person Owner; (exact classes have been changed to protect the innocent). To come up with the data for the graph, the user will choose whether it's a bar graph, scatter plot, etc., and then to actually obtain the data, I would like to obtain some kind of List from the user simply entering something SQL-ish along the lines of SELECT Name, AVG(WeighIns) FROM People SELECT WeightInKg, Owner.HeightInCm FROM Weights And as a bonus, it would be nice if you could actually do operations as well: SELECT WeightInKg, (Date - Owner.BirthDate) AS Age FROM Weights The DSL doesn't have to be compliant SQL in any way; it doesn't even have to resemble SQL, but I can't think of a more efficient descriptive language for the task. I'm fine filling in blanks; I don't expect a library to do everything for me. What I would expect to exist (but haven't been able to find in any way, shape, or form) is something like Fluent NHibernate (which I am already using in the project) where I can declare a mapping, something like var personRequest = Request<Person>(); personRequest.Item("Name", (p => p.Name)); personRequest.Item("HeightInCm", (p => p.HeightInCm)); personRequest.Item("HeightInInches", (p => p.HeightInCm * CM_TO_INCHES)); // ... var weightRequest = Request<Weight>(); weightRequest.Item("Owner", (w => w.Owner), personRequest); // Indicate a chain to personRequest // ... var people = Table<Person>("People", GetPeopleFromDatabase()); var weights = Table<Weight>("Weights", GetWeightsFromDatabase()); // ... TryRunQuery(userInputQuery); LINQ is so close to what I want to do, but AFAIK there's no way to sandbox it. I don't want to expose any unnecessary functionality to the end user; meaning I don't want the user to be able to send in and process: from p in people select (p => { System.IO.File.Delete("C:\\something\\important"); return p.Name }) So does anyone know of any free .NET libraries that allow something like what I've described above? Or is there some way to sandbox LINQ? cs-script is close too, but it doesn't seem to offer sandboxing yet either. I'd be hesitant to expose the NHibernate interface either, as the user should have a read-only view of the data at this point in the usage. I'm using C# 3.5, and pure .NET solutions would be preferred. The bottom line is that I'm really trying to avoid writing my own parser for a subset of SQL that would only apply to this single project.

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  • MySQL temp table issue

    - by AmyD
    Hi folks! I'm trying to use temp tables to speed up my MySQL 4.1.22-standard database and what seems like a simple operation is causing me all kinds of issues. My code is below.... CREATE TEMPORARY TABLE nonDerivativeTransaction_temp (accession_number varchar(30), transactionDateValue date)) TYPE=HEAP; INSERT INTO nonDerivativeTransaction_temp VALUES( SELECT accession_number, transactionDateValue FROM nonDerivativeTransaction WHERE transactionDateValue = "2010-06-15"); SELECT * FROM nonDerivativeTransaction_temp; The original table (nonDerivativeTransaction) has two fields, accession_number (varchar(30)) and transactionDateValue (date). Apparently I am getting an issue with the first two statements but I can't seem to nail down what it is. Any help would be appreciated. Amy D.

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  • Evaluate column value into rows

    - by Hugo Palma
    I have a column whose value is a json array. For example: [{"att1": "1", "att2": "2"}, {"att1": "3", "att2": "4"}, {"att1": "5", "att2": "6"}] What i would like is to provide a view where each element of the json array is transformed into a row and the attributes of each json object into columns. Keep in mind that the json array doesn't have a fixed size. Any ideas on how i can achieve this ?

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  • Java program runs smoothly in Netbeans but slowly in Eclipse and as an executed jar. WTF?

    - by comp sci balla
    A java program that does frequent swing/awt painting animation (but nothing more advanced than g.fillOval(...)) runs at a consistent 60fps in Netbeans, and at about 6fps when ran in Eclipse or executed as a jar file from a unix terminal. The program was developed in Netbeans and is run-of-the-mill desktop application (not webstart or japplet or ...). This is occurring in Ubuntu 10 with java 1.6. How is this possible? The universe no longer makes sense to me.

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  • Speed up :visible:input selector avoiding filter

    - by macca1
    I have a jQuery selector that is running way too slow on my unfortunately large page: $("#section").find(":visible:input").filter(":first").focus(); Is there a quicker way to select the first visible input without having to find ALL the visible inputs and then filtering THAT selection for the first? I want something like :visible:input:first but that doesn't seem to work.

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  • C++ code which is slower than its C equivalent?

    - by user997112
    Are there any aspects to the C++ programming language where the code is known to be slower than the equivalent C language? Obviously this would be excluding the OO features like virtual functions and vtable features etc. I am wondering whether, when you are programming in a latency-critical area (and you aren't worried about OO features) whether you could stick with basic C++ or would C be better?

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  • finding long repeated substrings in a massive string

    - by Will
    I naively imagined that I could build a suffix trie where I keep a visit-count for each node, and then the deepest nodes with counts greater than one are the result set I'm looking for. I have a really really long string (hundreds of megabytes). I have about 1 GB of RAM. This is why building a suffix trie with counting data is too inefficient space-wise to work for me. To quote Wikipedia's Suffix tree: storing a string's suffix tree typically requires significantly more space than storing the string itself. The large amount of information in each edge and node makes the suffix tree very expensive, consuming about ten to twenty times the memory size of the source text in good implementations. The suffix array reduces this requirement to a factor of four, and researchers have continued to find smaller indexing structures. And that was wikipedia's comments on the tree, not trie. How can I find long repeated sequences in such a large amount of data, and in a reasonable amount of time (e.g. less than an hour on a modern desktop machine)? (Some wikipedia links to avoid people posting them as the 'answer': Algorithms on strings and especially Longest repeated substring problem ;-) )

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  • fastest way to check to see if a certain index in a linq statement is null

    - by tehdoommarine
    Basic Details I have a linq statement that grabs some records from a database and puts them in a System.Linq.Enumerable: var someRecords = someRepoAttachedToDatabase.Where(p=>true); Suppose this grabs tons (25k+) of records, and i need to perform operations on all of them. to speed things up, I have to decided to use paging and perform the operations needed in blocks of 100 instead of all of the records at the same time. The Question The line in question is the line where I count the number of records in the subset to see if we are on the last page; if the number of records in subset is less than the size of paging - then that means there are no more records left. What I would like to know is what is the fastest way to do this? Code in Question int pageSize = 100; bool moreData = true; int currentPage = 1; while (moreData) { var subsetOfRecords = someRecords.Skip((currentPage - 1) * pageSize).Take(pageSize); //this is also a System.Linq.Enumerable if (subsetOfRecords.Count() < pageSize){ moreData = false;} //line in question //do stuff to records in subset currentPage++; } Things I Have Considered subsetOfRecords.Count() < pageSize subsetOfRecords.ElementAt(pageSize - 1) == null (causes out of bounds exception - can catch exception and set moreData to false there) Converting subsetOfRecords to an array (converting someRecords to an array will not work due to the way subsetOfRecords is declared - but I am open to changing it) I'm sure there are plenty of other ideas that I have missed.

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  • Slow in the Application, Fast in SSMS? Understanding Performance Mysteries

    When I read various forums about SQL Server, I frequently see questions from deeply mystified posters. They have identified a slow query or stored procedure in their application. They cull the SQL batch from the application and run it in SQL Server Management Studio (SSMS) to analyse it, only to find that the response is instantaneous. At this point they are inclined to think that SQL Server is all about magic. A similar mystery is when a developer has extracted a query in his stored procedure to run it stand-alone only to find that it runs much faster – or much slower – than inside the procedure.

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  • How to concatinate text on existing database entry?

    - by Starx
    I am a table, whose structure is somewhat like this id, name, link the link holds the name of the page like "link" = "index.php". Now I want to update this field and add "page=" in front of "index.php". Using this method I would like to update every entry in my table. My desired SQL syntax need to be something like this UPDATE mytable set link= 'page=' + <existing value of link> WHERE 1; I am using Where 1; to denote every other rows Anyone know what to accomplish this?

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  • Relating categories with tags using SQL

    - by Pablo
    I want be able to find tags of items under the a certain category. Following is example of my database design: images +----------+-----+-------------+-----+ | image_id | ... | category_id | ... | +----------+-----+-------------+-----+ | 1 | ... | 11 | ... | +----------+-----+-------------+-----+ | 2 | ... | 12 | ... | +----------+-----+-------------+-----+ | 3 | ... | 11 | ... | +----------+-----+-------------+-----+ | 4 | ... | 11 | ... | +----------+-----+-------------+-----+ images_tags +----------+--------+ | image_id | tag_id | +----------+--------+ | 1 | 53 | +----------+--------+ | 3 | 54 | +----------+--------+ | 2 | 55 | +----------+--------+ | 1 | 56 | +----------+--------+ | 4 | 57 | +----------+--------+ tags and categories each have their own table relating the id to an actual name(text). So my question is how will i find out that images with category_id=11 have have the tag_id 53 54 55 56 57. In other words how to find the tags that images in certain category have?

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  • Faster code with another compiler

    - by Andrei
    I'm using the standard gcc compiler in math software development with C-language. I don't know that much about compilers or compiler options, and I was just wondering, is it possible to make faster executables using another compiler or choosing better options? The default Makefile sets options -ffast-math and -O3 and I think both of them have some impact in the overall calculation time. My software is using memory quite extensively, so I imagine some options related to memory management might do the trick? Any ideas?

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  • Complex data ordering...

    - by Povylas
    Hi, I have one tables ids in an array and they are ordered in the way I want and I have to select data from another table using those ids and in a order they are listen in the array. Pretty confusing but I was thinking of two solutions giving ORDER BY parameter the array but I do not know if that possible and another is to get all the necessary data and then turn it to array (mysql_fetch_assoc) then compare those two and somehow order the new array using the ids array. But I also do not know how to do this... Any ideas?

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  • Cache bandwidth per tick for modern CPUs

    - by osgx
    Hello What is a speed of cache accessing for modern CPUs? How many bytes can be read or written from memory every processor clock tick by Intel P4, Core2, Corei7, AMD? Please, answer with both theoretical (width of ld/sd unit with its throughput in uOPs/tick) and practical numbers (even memcpy speed tests, or STREAM benchmark), if any. PS it is question, related to maximal rate of load/store instructions in assembler. There can be theoretical rate of loading (all Instructions Per Tick are widest loads), but processor can give only part of such, a practical limit of loading.

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  • Fast serialization/deserialization of structs

    - by user256890
    I have huge amont of geographic data represented in simple object structure consisting only structs. All of my fields are of value type. public struct Child { readonly float X; readonly float Y; readonly int myField; } public struct Parent { readonly int id; readonly int field1; readonly int field2; readonly Child[] children; } The data is chunked up nicely to small portions of Parent[]-s. Each array contains a few thousands Parent instances. I have way too much data to keep all in memory, so I need to swap these chunks to disk back and forth. (One file would result approx. 2-300KB). What would be the most efficient way of serializing/deserializing the Parent[] to a byte[] for dumpint to disk and reading back? Concerning speed, I am particularly interested in fast deserialization, write speed is not that critical. Would simple BinarySerializer good enough? Or should I hack around with StructLayout (see accepted answer)? I am not sure if that would work with array field of Parent.children. UPDATE: Response to comments - Yes, the objects are immutable (code updated) and indeed the children field is not value type. 300KB sounds not much but I have zillions of files like that, so speed does matter.

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  • NUll exception in filling a querystring by mocing framework

    - by user564101
    There is a simple controller that a querystring is read in constructor of it. public class ProductController : Controller { parivate string productName; public ProductController() { productName = Request.QueryString["productname"]; } public ActionResult Index() { ViewData["Message"] = productName; return View(); } } Also I have a function in unit test that create an instance of this Controller and I fill the querystring by a Mock object like below. [TestClass] public class ProductControllerTest { [TestMethod] public void test() { // Arrange var querystring = new System.Collections.Specialized.NameValueCollection { { "productname", "sampleproduct"} }; var mock = new Mock<ControllerContext>(); mock.SetupGet(p => p.HttpContext.Request.QueryString).Returns(querystring); var controller = new ProductController(); controller.ControllerContext = mock.Object; // Act var result = controller.Index() as ViewResult; // Assert Assert.AreEqual("Index", result.ViewName); } } Unfortunately Request.QueryString["productname"] is null in constructor of ProductController when I run test unit. Is ther any way to fill a querystrin by a mocking and get it in constructor of a control?

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  • Django ForeignKey _set on an inherited model

    - by neolaser
    I have two models Category and Entry. There is another model ExtEntry that inherits from Entry class Category(models.Model): title = models.CharField('title', max_length=255) description = models.TextField('description', blank=True) ... class Entry(models.Model): title = models.CharField('title', max_length=255) categories = models.ManyToManyField(Category) ... class ExtEntry(Entry): groups= models.CharField('title', max_length=255) value= models.CharField('title', max_length=255) ... I am able to use the Category.entry_set but I want to be able to do Category.blogentry_set but it is not available. If this is not available,then I need another method to get all ExtEntryrelated to one particular Category Thanks

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  • Selecting the 2nd row in sql

    - by Alex Chen
    I want to select the second row only from the table. From the ClientUserName column. SELECT ClientUserName, DestHost, count(DestHost) counts FROM #ProxyLog_record WHERE ClientUserName = (Select top 1 ClientUserName from #ProxyLog_count_2) GROUP BY ClientUserName, DestHost ORDER BY counts DESC The (Select top 1 ClientUserName from #ProxyLog_count_2) shows top 1 only but I need to get the 2nd data from that table. How can I do this?

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  • rails belongs_to sql statement using NULL id

    - by Team Pannous
    When paginating through our Phrase table it takes very long to return the results. In the sql logs we see many sql requests which don't make sense to us: Phrase Load (7.4ms) SELECT "phrases".* FROM "phrases" WHERE "phrases"."id" IS NULL LIMIT 1 User Load (0.4ms) SELECT "users".* FROM "users" WHERE "users"."id" IS NULL LIMIT 1 These add up significantly. Is there a way to prevent querying against null ids? This is the underlying model: class Phrase < ActiveRecord::Base belongs_to :user belongs_to :response, :class_name => "Phrase", :foreign_key => "next_id" end

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  • PHP – Slow String Manipulation

    - by Simon Roberts
    I have some very large data files and for business reasons I have to do extensive string manipulation (replacing characters and strings). This is unavoidable. The number of replacements runs into hundreds of thousands. It's taking longer than I would like. PHP is generally very quick but I'm doing so many of these string manipulations that it's slowing down and script execution is running into minutes. This is a pain because the script is run frequently. I've done some testing and found that str_replace is fastest, followed by strstr, followed by preg_replace. I've also tried individual str_replace statements as well as constructing arrays of patterns and replacements. I'm toying with the idea of isolating string manipulation operation and writing in a different language but I don't want to invest time in that option only to find that improvements are negligible. Plus, I only know Perl, PHP and COBOL so for any other language I would have to learn it first. I'm wondering how other people have approached similar problems? I have searched and I don't believe that this duplicates any existing questions.

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