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  • Recommended book for Sql Server query optimisation

    - by Patrick Honorez
    Even if I have made a certification exam on Sql Server Design and implementation , I have no clue about how to trace/debug/optimise performance in Sql Sever. Now the database I built is really business critical, and getting big, so it is time for me to dig into optimisation, specially regarding when/where to add indexes. Can you recommend a good book on this subject ? (smaller is better :) Just in case: I am using Sql Server 2008. Thanks

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  • Calculate value from two field in third field

    - by terence6
    I'm trying to create a query, that will calculate sum of products on invoice. I have 3 tables : Product (with product's price) Invoice (with invoice id) Products on invoice (with invoice id, product id and number of particular products) So in my query I take invoice_id (from invoice), price (from product),number of products sold and invoice_id (from products on invoice) and calculate their product in fourth column. I know I sohuld use 'Totals' but how to achieve that ? Model:

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  • Conditional PIVOT/transform problem

    - by IanC
    Hi folks I have a table with three columns, which we'll call ID1, ID2, and Value. Sample data: ID ID1 Value 1 1 0 1 2 1 1 3 1 1 3 2 1 4 0 1 4 1 1 5 0 1 5 2 2 1 2 Value is limited to 0, 1, or 2. What I need to do is pivot/transform this data into a column-based count of how many times each possible Value appears, grouped by ID, ID1. The output of the above should be: ID ID1 Val0 Val1 Val2 1 1 1 0 0 1 2 0 2 0 1 3 0 1 1 1 4 1 1 0 1 5 1 0 1 2 1 0 0 1 I'm using SQL Server 2008. How do I do this?

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  • Deleting unneeded rows from a table with 2 criteria

    - by stormbreaker
    Hello. I have a many-to-many relations table and I need to DELETE the unneeded rows. The lastviews table's structure is: | user (int) | document (int) | time (datetime) | This table logs the last users which viewed the document. (user, document) is unique. I show only the last 10 views of a document and until now I deleted the unneeded like this: DELETE FROM `lastviews` WHERE `document` = ? AND `user` NOT IN (SELECT * FROM (SELECT `user` FROM `lastviews` WHERE `document` = ? ORDER BY `time` DESC LIMIT 10) AS TAB) However, now I need to also show the last 5 documents a user has viewed. This means I can no longer delete rows using the previous query because it might delete information I need (say a user didn't view documents in 5 minutes and the rows are deleted) To sum up, I need to delete all the records that don't fit these 2 criterias: SELECT ... FROM `lastviews` WHERE `document` = ? ORDER BY `time` DESC LIMIT 10 and SELECT * FROM `lastviews` WHERE `user` = ? ORDER BY `time` DESC LIMIT 0, 5 I need the logic. Thanks in advance.

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  • When to use CTEs to encapsulate sub-results, and when to let the RDBMS worry about massive joins.

    - by IanC
    This is a SQL theory question. I can provide an example, but I don't think it's needed to make my point. Anyone experienced with SQL will immediately know what I'm talking about. Usually we use joins to minimize the number of records due to matching the left and right rows. However, under certain conditions, joining tables cause a multiplication of results where the result is all permutations of the left and right records. I have a database which has 3 or 4 such joins. This turns what would be a few records into a multitude. My concern is that the tables will be large in production, so the number of these joined rows will be immense. Further, heavy math is performed on each row, and the idea of performing math on duplicate rows is enough to make anyone shudder. I have two questions. The first is, is this something I should care about, or will SQL Server intelligently realize these rows are all duplicates and optimize all processing accordingly? The second is, is there any advantage to grouping each part of the query so as to get only the distinct values going into the next part of the query, using something like: WITH t1 AS ( SELECT DISTINCT... [or GROUP BY] ), t2 AS ( SELECT DISTINCT... ), t3 AS ( SELECT DISTINCT... ) SELECT... I have often seen the use of DISTINCT applied to subqueries. There is obviously a reason for doing this. However, I'm talking about something a little different and perhaps more subtle and tricky.

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  • Minimizing calls to database in rails

    - by ming yeow
    Hi guys, i am familiar with memcached and eager loading, but neither seems to solve the problem i am facing. My main performance lag comes from hundreds of data retrieval calls from the database. The tricky thing is that I do not know which set of users i need to retrieve until i have several steps of computation. I can refactor my code, but i was wondering how you experts handle this situation? I think it should be a fairly common situation def newsfeed - find out which users i need - retrieve those users via DB - find out which events happened for these users - for each of those events - retrieve new set of users - find out which groups are relevant - for each of those groups - retrieve new set of users - etc, etc end

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  • Speeding up a group by date query on a big table in postgres

    - by zaius
    I've got a table with around 20 million rows. For arguments sake, lets say there are two columns in the table - an id and a timestamp. I'm trying to get a count of the number of items per day. Here's what I have at the moment. SELECT DATE(timestamp) AS day, COUNT(*) FROM actions WHERE DATE(timestamp) >= '20100101' AND DATE(timestamp) < '20110101' GROUP BY day; Without any indices, this takes about a 30s to run on my machine. Here's the explain analyze output: GroupAggregate (cost=675462.78..676813.42 rows=46532 width=8) (actual time=24467.404..32417.643 rows=346 loops=1) -> Sort (cost=675462.78..675680.34 rows=87021 width=8) (actual time=24466.730..29071.438 rows=17321121 loops=1) Sort Key: (date("timestamp")) Sort Method: external merge Disk: 372496kB -> Seq Scan on actions (cost=0.00..667133.11 rows=87021 width=8) (actual time=1.981..12368.186 rows=17321121 loops=1) Filter: ((date("timestamp") >= '2010-01-01'::date) AND (date("timestamp") < '2011-01-01'::date)) Total runtime: 32447.762 ms Since I'm seeing a sequential scan, I tried to index on the date aggregate CREATE INDEX ON actions (DATE(timestamp)); Which cuts the speed by about 50%. HashAggregate (cost=796710.64..796716.19 rows=370 width=8) (actual time=17038.503..17038.590 rows=346 loops=1) -> Seq Scan on actions (cost=0.00..710202.27 rows=17301674 width=8) (actual time=1.745..12080.877 rows=17321121 loops=1) Filter: ((date("timestamp") >= '2010-01-01'::date) AND (date("timestamp") < '2011-01-01'::date)) Total runtime: 17038.663 ms I'm new to this whole query-optimization business, and I have no idea what to do next. Any clues how I could get this query running faster?

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  • Implementing "select distinct ... from ..." over a list of Python dictionaries

    - by daveslab
    Hi folks, Here is my problem: I have a list of Python dictionaries of identical form, that are meant to represent the rows of a table in a database, something like this: [ {'ID': 1, 'NAME': 'Joe', 'CLASS': '8th', ... }, {'ID': 1, 'NAME': 'Joe', 'CLASS': '11th', ... }, ...] I have already written a function to get the unique values for a particular field in this list of dictionaries, which was trivial. That function implements something like: select distinct NAME from ... However, I want to be able to get the list of multiple unique fields, similar to: select distinct NAME, CLASS from ... Which I am finding to be non-trivial. Is there an algorithm or Python included function to help me with this quandry? Before you suggest loading the CSV files into a SQLite table or something similar, that is not an option for the environment I'm in, and trust me, that was my first thought.

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  • Fancy dynamic list in Android: TableLayout vs ListView

    - by Ralkie
    There is a requirement to have not-so-trivial dynamic list, each record of which consists of several columns (texts, buttons). It should look something like: Text11 Text12 Button1 Button2 Text21 Text22 Button1 Button2 ... At first obvious way to accomplish that seemed to be TableLayout. I was expecting to have layout/styling data specified in res/layout/*.xml and to populate it with some dataset from java code (as with ListView, for which its possible to specify TextView of item in *.xml and bind it to some array using ArrayAdapter). But after playing for a while, all I found to be possible is fully populating TableLayout programatically. Still, creating TableRow by TableRow and setting layout attributes directly in java code doesn't seem elegant enough. So the questions are: Am I at the right path? Is TableLayout really best View to accomplish that? Maybe it's more appropriate to extend ListView or something else to meet such requirements? Is it possible to have TableLayout/TableRow template specified in *.xml and data bound to this template in java side?

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  • Java - How to change context root of a dynamic web project in eclipse

    - by Yatendra Goel
    I have developed a dynamic web project in eclipse. Now I can access it through my browser using the following url: http://localhost:8080/MyDynamicWebApp Now I want to change the access url to http://localhost:8080/app I changed the context root from the project properties | Web Project Settings | Context Root But it is not working. The web app still has the access url as earlier. I have re-deployed the application on tomcat, re-started the tomcat and have done everything that should be done but the access url is the same as earlier. I found that there were no server.xml file attached with the WARfile. The how the tomcat is determining that the context root of my web app is /MyDynamicWebApp and is allowing me to access the application through that url

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  • Fields_for dynamic label

    - by sebajb
    I have dynamic form which has a set of values. I created a partial which contains text fields which I display. Next to each of them I would like to display a label containing the title of the text. For instance First Name, and Last Name would not be known previously. How do I go about doing that? It seems that I cannot access the attributes directly. But when I use the label field, the variable name in the label is displayed not the actual value.

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  • Dynamic Tree control in Flex 3

    - by nimmyliji
    I am looking for sample code to create a dynamic Tree control in Flex using a Collection of objects obtained from the backend(Perl cgi). So, initially the Tree will display the root nodes. Clicking root node, will invoke the data for populating the child nodes (basically adding child nodes on demand). Clicking child nodes will pull another collection add child nodes of child node. So, lets assume Initially the Tree will display - Root1 Root2 Root3 Clicking Root1 will display something like this - Root1 Child 1 Child 2 Root2 Root3 And Clicking Child1 will display - Root1 Child 1 Child1 of Child 1 Child2 of Child 1 Child 2 Root2 Root3 Is it possible? Thanks in advance...

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  • Can a DevExpress XtraGrid be filled using a a Dynamic SELECT statement string

    - by Gerhard Weiss
    Can a DevExpress XtraGrid be filled using a a Dynamic SELECT statement string? i.e. SELECT * FROM Employee or SELECT * FROM Dependents To fill our XtraGrids currently, we use a ORM that creates entities. To do this it takes a lot of steps and time. What is driving me to ask this question is we do a lot of client aquistions where we get hundreds of files. I do not want to create entities for all of these then have to create an XtraGrid for each entity. Ideally if I can just feed it a SELECT statement and the XtraGrid could render it then I could use the XtraGrid very nice data minipulation features (Filter, Group By, etc). If you have any other ideas or suggestions please to not hesitate to post them.

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  • FF extension: a popup with dynamic menuitems, with each menu item having another popup

    - by encryptor
    I am building an extension that has a popup whose elements are constructed by a function call everytime the mouse hovers over the popup option. I am able to achieve this. Now I need to have a popup for each of the menu item (inside the original popup) which is not dynamic though. I have this code, but it does not work: var myMenuPopup = document.getElementById("file-popup4"); for (var m=0; m var newItem = document.createElement("menupopup"); newItem.setAttribute("label", publicdisplayname[m]); newItem.setAttribute("id", "public" + m); var new1 = document.createElement("menuitem"); new1.setAttribute("label","Home"); new1.setAttribute("id", "publichome" + m); newItem.onclick = function(){ } newItem.appendChild(new1); myMenuPopup.appendChild(newItem); but this doesnt work. Can someone please help me out with whats the problem

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  • Dynamic find methods Vs conditional statements

    - by piemesons
    Student.find(:all, :conditions => [‘name = ? and status = ?’ ‘mohit’, 1]) Vs Student.find_all_by_name_and_status(‘mohit’, 1) Both the queries will result the same set of row but first one is preferable cause in the second way there will be exception generated method_missing and then rails will try to relate it as dynamic method. if fine then result set to returned. Can any body explain me this in a good manner. What exactly is happening behind the screen. Please correct me if i am wrong.

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  • Constructing dynamic columns from parameters in Sybase

    - by Chapax
    Hi, I'm trying to write a stored proc (SP) in Sybase. The SP takes 5 varchar parameters. Based on the parameters passed, I want to construct the column names to be selected from a particular table. The below works: DECLARE @TEST VARCHAR(50) SELECT @TEST = "country" --print @TEST execute("SELECT DISTINCT id_country AS id_level, Country AS nm_level FROM tempdb..tbl_books INNER JOIN (tbl_ch2_bespoke_report INNER JOIN tbl_ch2_bespoke_rpt_mapping ON tbl_ch2_bespoke_report.id_report = tbl_ch2_bespoke_rpt_mapping.id_report) ON id_" + @TEST + "= tbl_ch2_bespoke_rpt_mapping.id_pnl_level WHERE tbl_ch2_bespoke_report.id_report = 14") but gives me multiple results: 1 1 row(s) affected. id_level nm_level 1 4376 XYZ 2 4340 ABC I would like to however only obtain the 2nd result. Do I need to necessarily use dynamic SQL to achieve this? Many thanks for your help. --Chapax

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  • Scrambling URLS for dynamic data

    - by ggonsalv
    What is the best method to obfuscate the urls created in Dynamic Data? eg \Products\List.aspx?ProductId=2 could become \Products\List.aspx?x=UHJvZHVjdElkPTI= where "ProductId=2" is base 64 encoded to prevent casual snooping on \Products\List.aspx?ProductId=3 \Products\List.aspx?ProductId=4 etc...? I will probably have to inherit from an existing object and override some function The question is which object and what function GetActionPath of the Metamodel object seems interesting, but how does the DynamicRoute "{table}/{Action}.aspx" play in into it... Right now on Asp.net 1.1 site I use an custom implementation of the following code. http://www.mvps.org/emorcillo/en/code/aspnet/qse.shtml It is HTTPModule that uses regular expression to rewrite all the querystrings and also with reflection changes the Querystring collection with decoded values. So where is the hook to affect the change.

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  • Determining if a .NET type is dynamic (created using Reflection.Emit)

    - by Diego Mijelshon
    While the .NET 4 framework provides the Assembly.IsDynamic method, that's not the case with .NET 2.0/3.5. The use case is simple: for logging purposes, I want to determine the underlying type name of an entity that might be wrapped by a dynamic proxy without having any references to NHibernate or Castle (which know about the proxy) For example, I might have a CatProxYadaYada, but I'm interested in Cat. What's the easiest way to get that type? I was thinking of this skeleton: var type = obj.GetType(); while (IsProxy_Dynamic_Whatever(obj)) type = type.BaseType; return type;

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  • MVC Form and Dictionary Type

    - by Brian Schmitt
    I am attempting to use a property on my model that is of type Dictionary<string, string>. This dictionary is one of several other properties on the model, and I am using the dictionary as a key/value store to produce a 'dynamic' form. E.G.: User Name Settings A B I want to be able to submit and save any changes to settings A and B. I can submit the form and get my posted values in all my other fields, however the dictionary gets set to null. <%=Html.LabelFor(m => m.Name)%> <%=Html.DisplayFor(m => m.Name)%> <%=Html.LabelFor(m => m.Settings["A"])%> <%=Html.TextBoxFor(m => m.Settings["A"])%> <%=Html.LabelFor(m => m.Settings["B"])%> <%=Html.TextBoxFor(m => m.Settings["B"])%> Is there a better way to produce the dynamic form with a key/value pair? The actual code will be using partials (there several hundred variations), and the above is only a contrived example.

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  • Simple Linq Dynamic Query question

    - by Dr. Zim
    In Linq Dynamic Query, Scott Guthrie shows an example Linq query: var query = db.Customers. Where("City == @0 and Orders.Count >= @1", "London", 10). OrderBy("CompanyName"). Select("new( CompanyName as Name, Phone)"); Notice the projection new( CompanyName as Name, Phone). If I have a class like this: public class CompanyContact { public string Name {get;set;} public string Phone {get;set;} } How could I essentially "cast" his result using the CompanyContact data type without doing a foreach on each record and dumping it in to a different data structure? To my knowledge the only .Select available is the Dymanic Query version which only takes a string and parameter list.

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  • To call SelectMany dynamically in the way of System.Linq.Dynamic

    - by user341127
    In System.Linq.Dynamic, there are a few methods to form Select, Where and other Linq statements dynamically. But there is no for SelectMany. The method for Select is as the following: public static IQueryable Select(this IQueryable source, string selector, params object[] values) { if (source == null) throw new ArgumentNullException("source"); if (selector == null) throw new ArgumentNullException("selector"); LambdaExpression lambda = DynamicExpression.ParseLambda(source.ElementType, null, selector, values); IQueryable result = source.Provider.CreateQuery( Expression.Call( typeof(Queryable), "Select", new Type[] { source.ElementType, lambda.Body.Type }, source.Expression, Expression.Quote(lambda))); return result; } I tried to modify the above code, after hours working, I couldn't find a way out. Any suggestions are welcome. Ying

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  • HTML + CSS dynamic render in flash?

    - by Ole Jak
    I have HTML + CSS text. I need some lib with simple function like "Render String Var conteining HTML" So no external files (like in flash lib called HTMLwraper you just have to play your SWF on top of HTML). dinamic! I give it string it renders It into some conteiner (not as a bitmab but as if it was real HTML dynamically rendered in flash). (And I need real HTML + CSS support not what normal rich text block gives us) I am going to use it in with Flex (Flash Builder) so I like MXML component model but even pure flash AS3 will workout. It should be Free and Opensource (any license like GPL, LGPL etc will be ok). So Is out there such flash\flex library for HTML + CSS dynamic rendering (rfom given String or XML)?

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  • Providing dynamic data to webpage

    - by Marius
    Hi, I have a web page that displays dynamic data which changes every 2 seconds. Data is selected from various data sources including Oracle. Currently, the page reloads every 10 seconds and runs a PHP script which retrieves the data and displays the page. I have other pages that gives a different view on the same data. This means the same query is run again for them as well. If I have 4 of these pages with 10 concurrent users each, suddenly the data retrieval happens 40 times every 10 seconds, obviously not ideal. I have some ideas on how to improve this situation, but I thought I would ask from some ideas from other experts that might have come across a similar situation. I'm not bound to PHP, and my server is on a Linux platform. Regards Marius

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  • Providing dynamic data to webpage

    - by Marius
    Hi, I have a web page that displays dynamic data which changes every 2 seconds. Data is selected from various data sources including Oracle. Currently, the page reloads every 10 seconds and runs a PHP script which retrieves the data and displays the page. I have other pages that gives a different view on the same data. This means the same query is run again for them as well. If I have 4 of these pages with 10 concurrent users each, suddenly the data retrieval happens 40 times every 10 seconds, obviously not ideal. I have some ideas on how to improve this situation, but I thought I would ask from some ideas from other experts that might have come across a similar situation. I'm not bound to PHP, and my server is on a Linux platform. Regards Marius

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  • How to return a dynamic value from a Mocha mock in Ruby

    - by Vivek
    The gist of my problem is as follows:- I'm writing a Mocha mock in Ruby for the method represented as "post_to_embassy" below. It is not really our concern, for the purpose of describing the problem, what the actual method does. But I need the mock to return a dynamic value. The proc '&prc' below is executing rightly in place of the actual method. But the "with" method in Mocha only allows for boolean values to be returned. So the code below outputs nil. I need it to output the value being passed through orderInfoXml. Does anyone know of an alternate method I can use? require 'rubygems' require 'mocha' include Mocha::API class EmbassyInterface def post_to_embassy(xml) puts "This is from the original class:-" puts xml return xml end end orderInfoXml = "I am THE XML" mock = EmbassyInterface.new prc = Proc.new do |orderXml| puts "This is from the mocked proc:-" puts orderXml orderXml end mock.stubs(:post_to_embassy).with(&prc) mock_result = mock.post_to_embassy(orderInfoXml) p mock_result #p prc.call("asd") output:- This is from the mocked proc:- I am THE XML nil

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