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• MySQL indexes: how do they work?

  - by bob-the-destroyer

  I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

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• how to prune data set?

  - by sakura90

  The MovieLens data set provides a table with columns: userid | movieid | tag | timestamp I have trouble reproducing the way they pruned the MovieLens data set used in: http://www.cse.ust.hk/~yzhen/papers/tagicofi-recsys09-zhen.pdf In 4.1 Data Set of the above paper, it writes "For the tagging information, we only keep those tags which are added on at least 3 distinct movies. As for the users, we only keep those users who used at least 3 distinct tags in their tagging history. For movies, we only keep those movies that are annotated by at least 3 distinct tags." I tried to query the database: select TMP.userid, count(*) as tagnum from (select distinct T.userid as userid, T.tag as tag from tags T) AS TMP group by TMP.userid having tagnum = 3; I got a list of 1760 users who labeled 3 distinct tags. However, some of the tags are not added on at least 3 distinct movies. Any help is appreciated.

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• SQL: join within same table with different 'where' clause

  - by Pmarcoen

  Ok, so the problem I'm facing is this, I have a table with 3 columns : ID, Key and Value. ID | Key | Value ================ 1 | 1 | ab 1 | 2 | cd 1 | 3 | ef 2 | 1 | gh 2 | 2 | ij 2 | 3 | kl Now I want to select the value of Keys 1 & 3 for all IDs, the return should be like this ID | 1 | 2 ================ 1 | ab | ef 2 | gh | kl So per ID 1 row containing the Values for Keys 1 & 3. I tried using 'join' but since I need to use multiple where clauses I can't figure out how to get this to work ..

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• How to create custom exception handler for custom controls or extension methods.

  - by Shantanu Gupta

  I am creating an extension method in C# to retrieve some value from datagridview. Here if a user gives column name that doesnot exists then i want this function to throw an exception that can be handled at the place where this function will be called. How can i achieve this. public static T Value<T>(this DataGridView dgv, int RowNo, string ColName) { if (!dgv.Columns.Contains(ColName)) throw new ArgumentException("Column Name " + ColName + " doesnot exists in DataGridView."); return (T)Convert.ChangeType(dgv.Rows[RowNo].Cells[ColName].Value, typeof(T)); }

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• Dynamically showing fields to a Dev Express Grid view on windows form

  - by Bhaskar

  In one of windows application in C# , I am using Dev Express Grid view control to bind some data and display it to user. I have custom business objects with properties defined for this purpose.Then I simple set the DataSource of the grid to the list of my custom business objects. A while ago , there came a requirement which means that the columns to be displayed on to the grid will be dynamic. This means I cannot know at design time which fields I will need to display. I was thinking of abandoning setting the DataSource and populating the grid manually by code. But I think this will cause many of the grid's features not to work properly, for example , grouping the data by drag n drop of fields to the header area etc. Is there any way to tell a grid at runtime to skip certain fields from a list of BO's when databinding to the grid ?

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• Different execution plan for similar queries

  - by Graham Clements

  I am running two very similar update queries but for a reason unknown to me they are using completely different execution plans. Normally this wouldn't be a problem but they are both updating exactly the same amount of rows but one is using an execution plan that is far inferior to the other, 4 secs vs 2 mins, when scaled up this is causing me a massive problem. The only difference between the two queries is one is using the column CLI and the other DLI. These columns are exactly the same datatype, and are both indexed exactly the same, but for the DLI query execution plan, the index is not used. Any help as to why this is happening is much appreciated. -- Query 1 UPDATE a SET DestKey = ( SELECT TOP 1 b.PrefixKey FROM refPrefixDetail AS b WHERE a.DLI LIKE b.Prefix + '%' ORDER BY len(b.Prefix) DESC ) FROM CallData AS a -- Query 2 UPDATE a SET DestKey = ( SELECT TOP 1 b.PrefixKey FROM refPrefixDetail b WHERE a.CLI LIKE b.Prefix + '%' ORDER BY len(b.Prefix) DESC ) FROM CallData AS a

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• Three level database - foreign keys

  - by poke

  I have a three level database with the following structure (simplified to only show the primary keys): Table A: a_id Table B: a_id, b_id Table C: a_id, b_id, c_id So possible values for table C would be something like this: a_id b_id c_id 1 1 1 1 1 2 1 1 3 1 2 1 1 2 2 2 1 1 2 2 1 2 2 2 ... I am now unsure, how foreign keys should be set; or if they should be set for the primary keys at all. My idea was to have a foreign key on table B B.a_id -> A.a_id, and two foreign key on C C.a_id -> A.a_id and ( C.a_id, C.b_id ) -> ( B.a_id, B.b_id ). Is that the way I should set up the foreign keys? Is the foreign key from C->A necessary? Or do I even need foreign keys at all given that all those columns are part of the primary keys? Thanks.

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• Why must "stride" in the System.Drawing.Bitmap constructor be a multiple of 4?

  - by Gorchestopher H

  I am writing an application that requires me to take a proprietary bitmap format (an MVTec Halcon HImage) and convert it into a System.Drawing.Bitmap in C#. The only proprietary functions given to me to help me do this involve me writing to file, except for the use of a "get pointer" function. This function is great, it gives me a pointer to the pixel data, the width, the height, and the type of the image. My issue is that when I create my System.Drawing.Bitmap using the constructor: new System.Drawing.Bitmap(width, height, stride, format, scan) I need to specify a "stride" that is a multiple of 4. This may be a problem as I am unsure what size bitmap my function will be hit with. Supposing I end up with a bitmap that is 111x111 pixels, I have no way to run this function other than adding a bogus column to my image or subtracting 3 columns. Is there a way I can sneak around this limitation?

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• SQL indexing on varchar

  - by alex

  I have a table whose columns are varchar(50) and a float - I need to (very quickly) look get the float associated with a given string. Even with indexing, this is rather slow. I know, however, that each string is associated with an integer, which I know at the time of lookup, so that each string maps to a unique integer, but each integer does not map to a unique string. One might think of it as a tree structure. Is there anything to be gained by adding this integer to the table, indexing on it, and using a query like SELECT floatval FROM mytable WHERE phrase=givenstring AND assoc=givenint? This is Postgres, and if you couldn't tell, I have very little experience with databases.

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• SQL CHECK constraint issues

  - by blahblah

  I'm using SQL Server 2008 and I have a table with three columns: Length, StartTime and EndTime. I want to make a CHECK constraint on this table which says that: if Length == NULL then StartTime <> NULL and EndTime <> NULL else StartTime == NULL and EndTime == NULL I've begun to try things like this: Length == NULL AND StartTime <> NULL AND EndTime <> NULL Obviously this is not enough, but even this simple expression will not validate. I get the error: "Error validating 'CK_Test_Length_Or_Time'. Do you want to edit the constraint?" Any ideas on how to go about doing this?

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• Mapping child objects in fluent nhibernate to a read-only view

  - by grenade

  Given that I am implementing a read-only UI, how do I create a ClassMap for Shop: public class Shop { public int Id { get; set; } public City City { get; set; } } public class City { public string Name { get; set; } public string CountryCode { get; set; } } The DB interface for Shops is a View containing 3 columns (ShopId, CityName, CountryCode). I was hoping to do something like this: public sealed class ShopMap : ClassMap<Shop> { public ShopMap() { Table("Shop"); Id(x => x.Id, "ShopId"); Map(x => x.City.Name, "CityName"); Map(x => x.City.CountryCode, "CountryCode"); } } Will fluent auto-instantiate Shop.City?

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• Looking for an easy cms system? flexible plugins modules, blocks, themes

  - by judi

  Hi I'm a big user of Wordpress however its not ideal for cms sites. I'm currently looking at pixie cms, however if say I want three columns, only one column can be allowed to change across pages and I can't apply specific templeates to pages. I'm also looking at impress cms which looks confusing in the admin although it has good reviews. Does anyone have any suggestions what is a flexible cms for a designer who only needs to edit the html and css and maybe add a news feed in one column. Thanks for your help Regards Judi

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• Restore Emacs Session/Desktop

  - by Patrick McLaren

  I've been searching for how to restore an emacs session, with no luck. I'm looking to restore all previously open buffers, some of which might contain erc, shells, directory listings, files, etc. Every time I open emacs, I spend a considerable amount of time arranging my buffers; splitting them into rows and columns, opening a shell, arranging irc channels. It takes a while to get onto work. I've tried adding the following to my init.el (desktop-save-mode 1) And then using M-x desktop-save. This only seems to restore files that are open, not shells or anything else running within buffers. I've also checked the following questions (sorry, not able to post links yet): Session management in emacs using Desktop library Emacs session / projects / window management Emacs: reopen buffers from last session on startup? And read through: DeskTop and EmacsSession at emacswiki.org/emacs/SessionManagement Here's a screenshot example of my emacs session. A simple answer would be to just focus on real work :P

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• Infopath form publishing and root content type ?

  - by Steve B

  Hi, I have several infopath 2010 form template that I want to publish to a form library in SharePoint 2010 Server with enterprise CaL. All of this forms have a common part (a template part actually). Is it possible to define a common "parent" content type of this forms ? In fact, I want : Form content type (SP OOB) My root form content type, with standard columns "requester", "process name", etc. Form 1 Form 2 etc. other unrelated form 1 other unrelated form 2 Instead of the standard behavior : Form content type (SP OOB) Form 1 Form 2 other unrelated form 1 other unrelated form 2 etc. Behind this question I want to be able to create a dashboard of all form request using a content query web, by simply specifying the content type ... One last word: the idea is to allow a customer (assuming its knowledge is limited to IP 2010 basic form design). So I can't accept answers like "extract files, use a text editor and hack the xsf file"... thx in advance

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• JPanel: both implementing my own paintComponent() and rendering children doesn't work

  - by Paul Marshall

  I'm extending a JPanel to display a game board, and adding a JEditorPane at the bottom to hold some status text. Unfortunately, the game board renders just fine, but the JEditorPane is just a blank gray area until I highlight the text in it, when it will render whatever text is highlighted (but not the rest). If I'm understanding Swing right, it should work, because super.paintComponent(g) should render the other children (i.e., the JEditorPane). Tell me, o great stackoverflow, what bonehead mistake am I making? public GameMap extends JPanel { public GameMap() { JEditorPane statusLines = new JEditorPane("text/plain","Stuff"); this.setLayout(new BoxLayout(this,BoxLayout.PAGE_AXIS)); this.add(new Box.Filler(/*enough room to draw my game board*/)); this.add(statusLines); } public void paintComponent(Graphics g){ super.paintComponent(g); for ( all rows ){ for (all columns){ //paint one tile } } } }

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• Regular Expression to break row with comma separated values into distinct rows

  - by Nick

  I have a file with many rows. Each row has a column which may contain comma separated values. I need each row to be distinct (ie no comma separated values). Here is an example row: AB AB10,AB11,AB12,AB15,AB16,AB21,AB22,AB23,AB24,AB25,AB99 ABERDEEN Aberdeenshire The columns are comma separated (Postcode area, Postcode districts, Post town, Former postal county). So the above row would get turned into: AB AB10 ABERDEEN Aberdeenshire AB AB11 ABERDEEN Aberdeenshire AB AB12 ABERDEEN Aberdeenshire ... ... I tried the following but it didn't work... (.+)\t(([0-9A-Z]+),)+\t(.+)\t(.+)

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• Delphi Clientdataset Lookup/Aggregate

  - by TheRoadrunner

  Hi, I need a little help with ClientDatasets in Delphi. What I want to achieve is a grid showing customers, where one of the columns shows the number of orders for each customer. I put a ClientDataset on a form and load Customers.xml from Delphi demo-data. Another ClienDataset is loaded with orders.xml. Relatively simple, I can define an aggregate on the orders CDS showing the total amount per customer (or the count). (See Cary Jensens article on this: http://edn.embarcadero.com/article/29272) The problem is getting this aggregate result from orders dataset into the customer dataset. It is kind of an reverse lookup, since there is a 1-n relationship between customers and orders, not an n-1 as normally in lookup scenarios. Any ideas ? Søren

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• Two Tables Serving as one Model in Rails

  - by matsko

  Is is possible in rails to setup on model which is dependant on a join from two tables? This would mean that for the the model record to be found/updated/destroyed there would need to be both records in both database tables linked together in a join. The model would just be all the columns of both tables wrapped together which may then be used for the forms and so on. This way when the model gets created/updated it is just one form variable hash that gets applied to the model? Is this possible in Rails 2 or 3?

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• Get data types from arbitrary sql statement in SQL Server 2008

  - by Christopherous 5000

  Given some arbitrary SQL I would like to get the data types of the returned columns. The statement might join many tables, views, TVFs, etc. I know I could create a view based on the query and get the datatypes from that, hoping there's a quicker way. Only think I've been able to think of is writing a .net utility to run the SQL and examine the results, wondering if there is a TSQL answer. i.e. Given (not real tables just an example) SELECT p.Name AS PersonName, p.Age, a.Account as AccountName FROM Person as p LEFT JOIN Account as a ON p.Id = a.OwnerId I would like to have something like PersonName: (nvarchar(255), not null) Age: (smallInt, not null) etc...

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• R counting the occurrences of similar rows of data frame

  - by Matt

  I have data in the following format called DF (this is just a made up simplified sample): eval.num, eval.count, fitness, fitness.mean, green.h.0, green.v.0, offset.0 random 1 1 1500 1500 100 120 40 232342 2 2 1000 1250 100 120 40 11843 3 3 1250 1250 100 120 40 981340234 4 4 1000 1187.5 100 120 40 4363453 5 1 2000 2000 200 100 40 345902 6 1 3000 3000 150 90 10 943 7 1 2000 2000 90 90 100 9304358 8 2 1800 1900 90 90 100 284333 However, the eval.count column is incorrect and I need to fix it. It should report the number of rows with the same values for (green.h.0, green.v.0, and offset.0) by only looking at the previous rows. The example above uses the expected values, but assume they are incorrect. How can I add a new column (say "count") which will count all previous rows which have the same values of the specified variables? I have gotten help on a similar problem of just selecting all rows with the same values for specified columns, so I supposed I could just write a loop around that, but it seems inefficient to me.

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• Silverlight Scrollable Content Problem

  - by Steve

  I am fairy new to Silverlight and I have a problem. I have a grid on a page that is resizable when the user resizes their browser window. In one of the grids columns I want to display dynamically added content that is scrollable, as there is more data than space available. I currently have a scrollViewer with a stack panel inside it, that i programmatically add a user control to and then several user controls to that control depending on the amount of content. My problem is this. The scrollViewer does not respect the available space and as such displays its content outside of the viewable area when there is more data than space. i.e. it does not uses it is not scrollable nature. Hopefully this is something simple that I have missed, but i am banging my head against the wall at the moment. Any help gratefully received.

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• How can I clip strings in Java2D and add ... in the end?

  - by Jonas

  I'm trying to print Invoices in a Java Swing applications. I do that by extending Printable and implement the method public int print(Graphics g, PageFormat pf, int page). I would like to draw strings in columns, and when the string is to long I want to clip it and let it end with "...". How can I measure the string and clip it at the right position? Some of my code: Font headline = new Font("Times New Roman", Font.BOLD, 14); g2d.setFont(headline); FontMetrics metrics = g2d.getFontMetrics(headline); g2d.drawString(myString, 0, 20); I.e How can I limit myString to be max 120px? I could use metrics.stringWidth(myString), but I don't get the position where I have to clip the string. Expected results could be: A longer string that exc... A shorter string. Another long string, but OK

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• MSSQL STOREDPROC SELECTING FROM A FIELD FROM 1 TABLE USING LIKE TO CREATE MORE THAN 1 COLUM IN A DAT

  - by djshortbus

  I have a ASPX.NET DataGrid and im trying to USE a select LIKE 'X'% from a table that has 1 field called location. im trying to display the locations that start with a certain letter (example wxxx,axxx,fxxx,) in different columns in my data grid. SELECT DISTINCT LM.LOCATION AS '0 LOCATIONS' , LM.COUNTLEVEL AS 'COUNTLEVEL' FROM SOH S WITH(NOLOCK) JOIN LOCATIONMASTER LM ON LM.LMID = S.LMID WHERE LM.COUNTLEVEL = 1 AND LM.LOCATION NOT IN ('RECOU','PROBLEM','TOSTOCK','PYXVLOC') AND LM.LOCATION LIKE '0%' SELECT DISTINCT LM.LOCATION AS 'A LOCATIONS' , LM.COUNTLEVEL AS 'COUNTLEVEL' FROM SOH S WITH(NOLOCK) JOIN LOCATIONMASTER LM ON LM.LMID = S.LMID WHERE LM.COUNTLEVEL = 1 AND LM.LOCATION NOT IN ('RECOU','PROBLEM','TOSTOCK','PYXVLOC') AND LM.LOCATION LIKE 'A%'

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• Web-based JSON editor that works like property explorer with AJAXy input form

  - by dreftymac

  Background: This is a request for something that may not exist yet, but I've been meaning to build one for a long time. First I will ask if anyone has seen anything like it yet. Suppose you have an arbitrary JSON structure like the following: { 'str_title':'My Employee List' ,'str_lastmod': '2009-June-15' ,'arr_list':[ {'firstname':'john','lastname':'doe','age':'33',} ,{'firstname':'jane','lastname':'doe','age':'34',} ,{'firstname':'samuel','lastname':'doe','age':'35',} ] } Question: Is there a web-based JSON editor that could take a structure like this, and automatically allow the user to modify this in a user-friendly GUI? Example: Imagine an auto-generated HTML form that displays 2 input-type-text controls for both title and lastmod, and a table of input-type-text controls with three columns and three rows for arr_list ... with the ability to delete or add additional rows by clicking on a [+][X] next to each row in the table. Big Idea: The "big idea" behind this is that the user would be able to specify any arbitrary (non-recursive) JSON structure and then also be able to edit the structure with a GUI-based interaction (this would be similar to the "XML Editor Grid View" in XML Spy).

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• ItemsControl that loads items one by one asynchronously.

  - by Vinit Sankhe

  Hey Guys, I am creating a custom DataGrid by deriving the traditional tookit based WPF DataGrid. I want a functionality in the grid to load items one by one asynchronously, wherein as soon as ItemsSource is changed i.e. a new collection is Set to the ItemsSource property or the bound collection is Changed dues to items that rae added, moved or removed (wherein the notifications comes to the data grid when the underlying source implements INotifyCollectionChanged such as ObservableCollection). This is because even with virtualising stackpanel underneath the datagrid takes time to load (2-3 seconds delay) to load the data rows when it has several columns and some are template based. With above behavior that delay would "appear" to have reduced giving datagrid a feel that it has the data and is responsive enough to load it. How can I achieve it? Thx Vinit.

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