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• Database schema for Product Properties

  - by Chemosh

  As so many people I'm looking for a Products /Product Properties database schema. I'm using Ruby on Rails and (Thinking) Sphinx for faceted searches. Requirements: Adding new product types and their options should not require a change to the database schema Support faceted searches using Sphinx. Solutions I've come across: (See Bill Karwin's answer) Option 1: Single Table Inheritance Not an option really. The table would contain way to many columns. Option 2: Class Table Inheritance Ruby on Rails caches the database schema on start-up which means a restart whenever a new type of product is introduced. If you have a size able product catalog this could mean hundreds of tables. Option 3: Serialized LOB Kills being able to do faceted searches without heavy application logic. Option 4: Entity-Attribute-Value For testing purposes, EAV worked fine. However it could quickly become a mess and a maintenance hell as you add more and more options (e.g. when an option increase the prices or delivery time). What option should I go with? What other solutions are out there? Is there a silver bullet (ha) I overlooked?

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• C# Dataset Dynamically Add DataColumn

  - by Wesley

  I am trying to add a extra column to a dataset after a query has completed. I have a database relationship of the following: Employees / \ Groups EmployeeGroups Empoyees holds all the data for that individual, I'll name the unique key the UserID. Groups holds all the groups that a employee can be a part of, i.e. Super User, Admin, User; etc. I will name the unique key GroupID EmployeeGroups holds all the associations of which groups each employee belongs too. (UserID | GroupID) What I am trying to accomplish is after querying for a all users I want to loop though each user and add what groups that user is a part of by adding a new column to the dataset named 'Groups' which is a string to insert the values of the next query to get all the groups that user is a part of. Then by user of databinding populate a listview with all employees and their group associations My code is as follows; Position 5 is the new column I am trying to add to the dataset. string theQuery = "select UserID, FirstName, LastName, EmployeeID, Active from Employees"; DataSet theEmployeeSet = itsDatabase.runQuery(theQuery); DataColumn theCol = new DataColumn("Groups", typeof(string)); theEmployeeSet.Tables[0].Columns.Add(theCol); foreach (DataRow theRow in theEmployeeSet.Tables[0].Rows) { theRow.ItemArray[5] = "1234"; } At the moment, the code will create the new column but when i assign the data to that column nothing will be assigned, what am I missing? If there is any further explination or information I can provide, please let me know. Thank you all

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• WPF ListView Button - Associate multiple images

  - by Narayanan

  I have a listview in a WPF application that has a button in one of its columns. I associate a image to the button control. I want to configure different images for this button based on the How do I write the XAML in this scenario??? This is what I have already: <ControlTemplate x:Key="IconButtonAddProfile" TargetType="{x:Type Button}"> <Grid> <Image x:Name="myimage" Source="rofile.png" Height="27" Width="65" /> <Border> <ContentPresenter Content="{TemplateBinding Content}"/> </Border> </Grid> </ControlTemplate> <ListView.View> <GridView> <GridViewColumn Header="Security" Width="50"> <GridViewColumn.CellTemplate> <DataTemplate> <Button Template="{StaticResource IconButtonLockSecure}" DataContext="{Binding}" MinHeight="20" MinWidth="50" /> </DataTemplate> </GridViewColumn.CellTemplate> </GridViewColumn> </ListView.View>

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• CSS Flexible Height with scrollable content

  - by th3hamburgler

  I'm looking to create a flexible width/height page layout with no window scrollbars! Any content that will not fit on the page should be scrollable independently with the overflow property. I've seen plenty of ways to construct flexible width layouts using just HTML and CSS. The following site does a pretty good job on that front: http://ago.tanfa.co.uk/css/layouts/css-3-column-layout-v1.html I wish to implement scrollable content within the 3 centre columns. The content should be scrollable not the column div. e.g. <div class="column"> <h4>Title</h4> <ul> <li>These</li> <li>Items</li> <li>Should</li> <li>Be</li> <li>Scrollable</li> <li>If</li> <li>They</li> <li>Exceed</li> <li>The</li> <li>Window</li> <li>Height</li> </ul> So far if the list exceeds the window height it pushes the footer off page. I'm not to bothered about it working on old versions of IE, although that would score bonus points!

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• problem in html, table class text stretching out.

  - by Andy

  Hey people, I've got a slight problem after weeks of html programming. I've got a large table which I use to construct tabs with, details don't really matter. On every tab there is a tab title (which is defined as one single cell in a table with a class from a .css) and under it there are other rows and columns for the table. sample code for the single table with the single cell in it: <table class='tabcontainer_title'><tr><td class='tabcontainer_title'>TEXT</td></tr></table> This table is again positioned in one cell of the table outside it, which has a different class 'tabcontainer_content' This is in the CSS: .tabcontainer_title{ background-color : #58af34; background-image : url(); text-align : right; vertical-align : top; margin-top : 0px; margin-right : 0px; margin-bottom : 0px; margin-left : 0px; padding-top : 5px; padding-right : 10px; padding-bottom : 5px; padding-left : 0px; font-size : 14px; font-style : normal; color : #000000; } .tabcontainer_content{ width : 100%; font-weight : bolder; background-color : #58af34; color : #000000; padding : 0px; border-collapse : collapse; } The problem I'm experiencing right now is that if there are like 3 rows in the table, which means there's a lot of emtpy space instead of those rows, the text in the tab title has a large margin from the top: but I haven't configured any margin to be present. When the table is full of rows though, hence the table is full, then the tab title holds no unnecessary empty space above the text. What am I missing here?

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• Devexpress Repository ComboBoxEdit loosing cursor position. Edit.SelectionStart Not being assigned

  - by user575219

  I am having an issue with my comboBoxEdit in a gridcontrol. I am using Winforms Devepress 11.2. I clicked in the text of an existing Repository comboBoxEdit, and typed in "appear backwards", however, it displayed as "sdrawkcab raeppa" like it would in a mirror. There are some posts about this topic but none of the solutions seem to work The reason for this is the following foreach (GridColumn column in this.gvNotes.Columns) { var columnEdit = column.ColumnEdit; if (columnEdit != null) { column.ColumnEdit.EditValueChanged += this.PostEditValueChanged; } } private void PostEditValueChanged(object sender, EventArgs e) { this.gvNotes.PostEditor(); } This PostEditor ensures the save button is enabled when the user is still in the current cell. The user does not need to leave the cell or change column for the changes to be posted to the grid. So this is what I did: private void PostEditValueChanged(object sender, EventArgs e) { ComboBoxEdit edit = this.gridNotes.FocusedView.ActiveEditor as ComboBoxEdit; if (edit != null) { int len = edit.SelectionLength; int start = edit.SelectionStart; gridNotes.FocusedView.PostEditor(); edit.SelectionLength = len; edit.SelectionStart = start; } This did not solve the problem of the cursor resetting to the start position. Edit.SelectionStart is not being assinged to the len value.Even though len changes to 1 edit.SelectionStart remains at 0 Does anyone know what event needs to be handled to not loose the cursor position?

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• Is it a good idea to use MySQL and Neo4j together?

  - by Sanoj

  I will make an application with a lot of similar items (millions), and I would like to store them in a MySQL database, because I would like to do a lot of statistics and search on specific values for specific columns. But at the same time, I will store relations between all the items, that are related in many connected binary-tree-like structures (transitive closure), and relation databases are not good at that kind of structures, so I would like to store all relations in Neo4j which have good performance for this kind of data. My plan is to have all data except the relations in the MySQL database and all relations with item_id stored in the Neo4j database. When I want to lookup a tree, I first search the Neo4j for all the item_id:s in the tree, then I search the MySQL-database for all the specified items in a query that would look like: SELECT * FROM items WHERE item_id = 45 OR item_id = 345435 OR item_id = 343 OR item_id = 78 OR item_id = 4522 OR item_id = 676 OR item_id = 443 OR item_id = 4255 OR item_id = 4345 Is this a good idea, or am I very wrong? I haven't used graph-databases before. Are there any better approaches to my problem? How would the MySQL-query perform in this case?

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• iPhone and iPad : Doing a "select * from something" query in a SQLite database

  - by Abramodj

  Hi folks, i'm trying to use the SQLite data base in my iPad app, and here's my function to make a query: - (void)executeQuery:(char*)query { NSString *file = [self getWritableDBPath]; NSFileManager *fileManager = [NSFileManager defaultManager]; BOOL success = [fileManager fileExistsAtPath:file]; // If its not a local copy set it to the bundle copy if(!success) { //file = [[NSBundle mainBundle] pathForResource:DATABASE_TITLE ofType:@"db"]; [self createEditableCopyOfDatabaseIfNeeded]; } dataArray = NULL; dataArray = [NSMutableArray array]; sqlite3 *database = NULL; if (sqlite3_open([file UTF8String], &database) == SQLITE_OK) { sqlite3_exec(database, query, loadTimesCallback, dataArray, NULL); } sqlite3_close(database); [self logResults]; } if I call [self executeQuery:"select name from table1"]; everything is working fine. But if i call [self executeQuery:"select * from cars"]; the app crashes telling me that the NSMutableArray dataArray is not the right kind of variable where to set the query results. So, how can i do a "select * form table1" query, and store the results? Thanks! EDIT: Here's my loadTimesCallback method: static int loadTimesCallback(void *context, int count, char **values, char **columns) { NSMutableArray *times = (NSMutableArray *)context; for (int i=0; i < count; i++) { const char *nameCString = values[i]; [times addObject:[NSString stringWithUTF8String:nameCString]]; } return SQLITE_OK; }

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• How to Map Two Tables To One Class in Fluent NHibernate

  - by Richard Nagle

  I am having a problem with fluent nhiberbate mapping two tables to one class. I have the following database schema: TABLE dbo.LocationName ( LocationId INT PRIMARY KEY, LanguageId INT PRIMARY KEY, Name VARCHAR(200) ) TABLE dbo.Language ( LanguageId INT PRIMARY KEY, Locale CHAR(5) ) And want to build the following class definition: public class LocationName { public virtual int LocationId { get; private set; } public virtual int LanguageId { get; private set; } public virtual string Name { get; set; } public virtual string Locale { get; set; } } Here is my mapping class: public LocalisedNameMap() { WithTable("LocationName"); UseCompositeId() .WithKeyProperty(x => x.LanguageId) .WithKeyProperty(x => x.LocationId); Map(x => x.Name); WithTable("Language", lang => { lang.WithKeyColumn("LanguageId"); lang.Map(x => x.Locale); }); } The problem is with the mapping of the Locale field being from another table, and in particular that the keys between those tables don't match. Whenever I run the application with this mapping I get the following error on startup: Foreign key (FK7FC009CCEEA10EEE:Language [LanguageId])) must have same number of columns as the referenced primary key (LocationName [LanguageId, LocationId]) How do I tell nHibernate to map from LocationName to Language using only the LanguageId field?

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• Updating target workbook - extracting data from source workbook

  - by Allan

  My question is as follows: I have given a workbook to multiple people. They have this workbook in a folder of their choice. The workbook name is the same for all people, but folder locations vary. Let's assume the common file name is MyData-1.xls. Now I have updated the workbook and want to give it to these people. However when they receive the new one (let's call it MyData-2.xls) I want specific parts of their data pulled from their file (MyData-1) and automatically put into the new one provided (MyData-2). The columns and cells to be copied/imported are identical for both workbooks. Let's assume I want to import cell data (values only) from MyData-1.xls, Sheet 1, cells B8 through C25 ... to ... the same location in the MyData-2.xls workbook. How can I specify in code (possibly attached to a macro driven import data now button) that I want this data brought into this new workbook. I have tried it at my own location by opening the two workbooks and using the copy/paste-special with links process. It works really well, but It seems to create a hard link between the two physical workbooks. I changed the name of the source workbook and it still worked. This makes me believe that there is a "hard link" between the tow and that this will not allow me to give the target (MyData-2.xls) workbook to others and have it find their source workbook.

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• Need help with many-to-many relationships....

  - by yuudachi

  I have a student and faculty table. The primary key for student is studendID (SID) and faculty's primary key is facultyID, naturally. Student has an advisor column and a requested advisor column, which are foreign key to faculty. That's simple enough, right? However, now I have to throw in dates. I want to be able to view who their advisor was for a certain quarter (such as 2009 Winter) and who they had requested. The result will be a table like this: Year | Term | SID | Current | Requested ------------------------------------------------ 2009 | Winter | 860123456 | 1 | NULL 2009 | Winter | 860445566 | 3 | NULL 2009 | Winter | 860369147 | 5 | 1 And then if I feel like it, I could also go ahead and view a different year and a different term. I am not sure how these new table(s) will look like. Will there be a year table with three columns that are Fall, Spring and Winter? And what will the Fall, Spring, Winter table have? I am new to the art of tables, so this is baffling me... Also, I feel I should clarify how the site works so far now. Admin can approve student requests, and what happens is that the student's current advisor gets overwritten with their request. However, I think I should not do that anymore, right?

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• jQuery adding a row to a table with click() handler for tr

  - by Dave

  I'm having an issue with a control I'm building that contains a table where the body is scrollable. The rows have a click() function handler established like: /** * This function is called when the user clicks the mouse on a row in * our scrolling table. */ $('.innerTable tr').click (function (e) { // // Only react to the click if the mouse was clicked in the DIV or // the TD. // if (event.target.nodeName == 'DIV' || event.target.nodeName == 'TD' ) { // // If the user wasn't holding down the control key, then deselect // any previously selected columns. // if (e.ctrlKey == false) { $('.innerTable tr').removeClass ('selected'); } // // Toggle the selected state of the row that was clicked. // $(this).toggleClass ('selected'); } }); There is a button that adds rows to the table like: $('#innerTable > tbody:last').append('<tr>...some information...</tr>'); While the rows ARE added successfully, for some reason, the static rows work with the click handler, but the newly added rows do not. Is there something I'm missing? Thanks in advance!

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• How to add an array value to the middle of an associative array?

  - by Citizen

  Lets say I have this array: $array = array('a'=>1,'z'=>2,'d'=>4); Later in the script, I want to add the value 'c'=>3 before 'z'. How can I do this? EDIT: Yes, the order is important. When I run a foreach() through the array, I do NOT want this newly added value added to the end of the array. I am getting this array from a mysql_fetch_assoc() EDIT 2: The keys I used above are placeholders. Using ksort() will not achieve what I want. EDIT 3: http://www.php.net/manual/en/function.array-splice.php#88896 accomplishes what I'm looking for but I'm looking for something simpler. EDIT 4: Thanks for the downvotes. I gave feedback to your answers and you couldn't help, so you downvoted and requested to close the question because you didn't know the answer. Thanks. EDIT 5: Take a sample db table with about 30 columns. I get this data using mysql_fetch_assoc(). In this new array, after column 'pizza' and 'drink', I want to add a new column 'full_dinner' that combines the values of 'pizza' and 'drink' so that when I run a foreach() on the said array, 'full_dinner' comes directly after 'drink'

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• Google App-Engine Java Batch Update

  - by Manjoor

  I need to upload a .csv file and save the records in bigtable. My application successfully parse 200 the records in the csv files and save to table. Here is my code to save the data. for (int i=0;i<lines.length -1;i++) //lines hold total records in csv file { String line = lines[i]; //The record have 3 columns integer,integer,Text if(line.length() > 15) { int n = line.indexOf(","); if (n>0) { int ID = lInteger.parseInt(ine.substring(0,n)); int n1 = line.indexOf(",", n + 2); if(n1 > n) { int Col1 = Integer.parseInt(line.substring(n + 1, n1)); String Col2 = line.substring(n1 + 1); myTable uu = new myTable(); uu.setId(ID); uu.setCol1(MobNo); Text t = new Text(Col2); uu.setCol2(t); PersistenceManager pm = PMF.get().getPersistenceManager(); pm.makePersistent(uu); pm.close(); } } } } But when no of records grow it gives timeout error. The csv file may have upto 800 records. Is it possible to do that in App-Engine? (something like batch update)

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• Presenting collection of structures of strings in grid or similar in WPF - Example? Ideas?

  - by Andrew

  Hi, I have a collection of structures. The structure is just some strings. Example public struct ReportLine { public string Name; public string Address; public string Phone; ...// about 10 other strings } I can't change this part. What I want to do is display it in a simple grid or simlar in WPF. My only requirements are: a) need column headers b) rows must alternate in color c) columns big enough to hold largest datum (which is not know until run time) Can someone point me to an example to get me started? Is the GridView the way to go? Or DataGrid? Or perhaps just the grid? I have the book Pro WPF in C# 2008 and it covers binding ListBox's to collections, but the collections always seem to be collections of one field (ex. a collection of 40 names). Here I have a collection (an array in fact) of a structure. How do I setup the databinding? As you can see, I'm new to this and probably would most benefit from a reference to an article. I've found articles covering collections of 1 field, but no examples covering binding to an array of structures. Also, my intitial research indicates c) can't be easily done, if you demand that the column is big enough for all the data in that column, not just the visible data. Thanks, dave

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• import csv file/excel into sql database asp.net

  - by kiev

  Hi everyone! I am starting a project with asp.net visual studio 2008 / SQL 2000 (2005 in future) using c#. The tricky part for me is that the existing DB schema changes often and the import files columns will all have to me matched up with the existing db schema since they may not be one to one match on column names. (There is a lookup table that provides the tables schema with column names I will use) I am exploring different ways to approach this, and need some expert advice. Is there any existing controls or frameworks that I can leverage to do any of this? So far I explored FileUpload .NET control, as well as some 3rd party upload controls to accomplish the upload such as SlickUpload but the files uploaded should be < 500mb Next part is reading of my csv /excel and parsing it for display to the user so they can match it with our db schema. I saw CSVReader and others but for excel its more difficult since I will need to support different versions. Essentially The user performing this import will insert and/or update several tables from this import file. There are other more advance requirements like record matching but and preview of the import records, but I wish to get through understanding how to do this first. Update: I ended up using csvReader with LumenWorks.Framework for uploading the csv files.

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• ADO.NET DataTable/DataRow Thread Safety

  - by Allen E. Scharfenberg

  Introduction A user reported to me this morning that he was having an issue with inconsistent results (namely, column values sometimes coming out null when they should not be) of some parallel execution code that we provide as part of an internal framework. This code has worked fine in the past and has not been tampered with lately, but it got me to thinking about the following snippet: Code Sample lock (ResultTable) { newRow = ResultTable.NewRow(); } newRow["Key"] = currentKey; foreach (KeyValuePair<string, object> output in outputs) { object resultValue = output.Value; newRow[output.Name] = resultValue != null ? resultValue : DBNull.Value; } lock (ResultTable) { ResultTable.Rows.Add(newRow); } (No guarantees that that compiles, hand-edited to mask proprietery information.) Explanation We have this cascading type of locking code other places in our system, and it works fine, but this is the first instance of cascading locking code that I have come across that interacts with ADO .NET. As we all know, members of framework objects are usually not thread safe (which is the case in this situation), but the cascading locking should ensure that we are not reading and writing to ResultTable.Rows concurrently. We are safe, right? Hypothesis Well, the cascading lock code does not ensure that we are not reading from or writing to ResultTable.Rows at the same time that we are assigning values to columns in the new row. What if ADO .NET uses some kind of buffer for assigning column values that is not thread safe--even when different object types are involved (DataTable vs. DataRow)? Has anyone run into anything like this before? I thought I would ask here at StackOverflow before beating my head against this for hours on end :) Conclusion Well, the consensus appears to be that changing the cascading lock to a full lock has resolved the issue. That is not the result that I expected, but the full lock version has not produced the issue after many, many, many tests. The lesson: be wary of cascading locks used on APIs that you do not control. Who knows what may be going on under the covers!

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• Question about the benefit of using an ORM

  - by johnny

  I want to use an ORM for learning purposes and am try nhibernate. I am using the tutorial and then I have a real project. I can go the "old way" or use an ORM. I'm not sure I totally understand the benefit. On the one hand I can create my abstractions in code such that I can change my databases and be database independent. On the other it seems that if I actually change the database columns I have to change all my code. Why wouldn't I have my application without the ORM, change my database and change my code, instead of changing my database, orm, and code? Is it that they database structure doesn't change that much? I believe there are real benefits because ORMs are used by so many. I'm just not sure I get it yet. Thank you. EDIT: In the tutorial they have many files that are used to make the ORM work http://www.hibernate.org/362.html In the event of an application change, it seems like a lot of extra work just to say that I have "proper" abstraction layers. Because I'm new at it it doesn't look that easy to maintain and again seems like extra work, not less.

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• Use MySQL trigger to update another table when duplicate key found

  - by Jason

  Been scratching my head on this one, hoping one of you kind people and direct me towards solving this problem. I have a mysql table of customers, it contains a lot of data, but for the purpose of this question, we only need to worry about 4 columns 'ID', 'Firstname', 'Lastname', 'Postcode' Problem is, the table contains a lot of duplicated customers. A new table is being created where each customer is unique and for us, we decide a unique customer is based on 'Firstname', 'Lastname' and 'Postcode' However, (this is the important bit) we need to ensure each new "unique" customer record also can be matched to the original multiple entries of that customer in the original table. I believe the best way to do this is to have a third table, that has 'NewUniqueID', 'OldCustomerID'. So we can search this table for 'NewUniqueID' = '123' and it would return multiple 'OldCustomerID' values where appropriate. I am hoping to make this work using a trigger and the on duplicate key syntax. So what would happen is as follows: An query is run taking the old customer table and inserting it in to the new unique table. (A standard Insert Select query) On duplicate key continue adding records, but add one entry in to the third table noting the 'NewUniqueID' that duped along with the 'OldCustomerID' of the record we were trying to insert. Hope this makes sense, my apologies if it isn't clear. I welcome and appreciate any thoughts on this one! Many thanks Jason

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• Best way to migrate export/import from SQL Server to oracle

  - by matao

  Hi guys! I'm faced with needing access for reporting to some data that lives in Oracle and other data that lives in a SQL Server 2000 database. For various reasons these live on different sides of a firewall. Now we're looking at doing an export/import from sql server to oracle and I'd like some advice on the best way to go about it... The procedure will need to be fully automated and run nightly, so that excludes using the SQL developer tools. I also can't make a live link between databases from our (oracle) side as the firewall is in the way. The data needs to be transformed in the process from a star schema to a de-normalised table ready for reporting. What I'm thinking about is writing a monster query for SQL Server (which I mostly have already) that will denormalise and read out the data from SQL Server into a flat file using the sql server equivalent of sqlplus as a scheduled task, dump into a Well Known Location, then on the oracle side have a cron job that copies down the file and loads it with sql loader and rebuilds indexes etc. This is all doable, but very manual. Is there one or a combination of FOSS or standard oracle/SQL Server tools that could automate this for me? the Irreducible complexity is the query on one side and building indexes on the other, but I would love to not have to write the CSV dumping detail or the SQL loader script, just say dump this view out to CSV on one side, and on the other truncate and insert into this table from CSV and not worry about mapping column names and all other arcane sqlldr voodoo... best practices? thoughts? comments? edit: I have about 50+ columns all of varying types and lengths in my dataset, which is why I'd prefer to not have to write out how to generate and map each single column...

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• ndarray field names for both row and column?

  - by Graham Mitchell

  I'm a computer science teacher trying to create a little gradebook for myself using NumPy. But I think it would make my code easier to write if I could create an ndarray that uses field names for both the rows and columns. Here's what I've got so far: import numpy as np num_stud = 23 num_assign = 2 grades = np.zeros(num_stud, dtype=[('assign 1','i2'), ('assign 2','i2')]) #etc gv = grades.view(dtype='i2').reshape(num_stud,num_assign) So, if my first student gets a 97 on 'assign 1', I can write either of: grades[0]['assign 1'] = 97 gv[0][0] = 97 Also, I can do the following: np.mean( grades['assign 1'] ) # class average for assignment 1 np.sum( gv[0] ) # total points for student 1 This all works. But what I can't figure out how to do is use a student id number to refer to a particular student (assume that two of my students have student ids as shown): grades['123456']['assign 2'] = 95 grades['314159']['assign 2'] = 83 ...or maybe create a second view with the different field names? np.sum( gview2['314159'] ) # total points for the student with the given id I know that I could create a dict mapping student ids to indices, but that seems fragile and crufty, and I'm hoping there's a better way than: id2i = { '123456': 0, '314159': 1 } np.sum( gv[ id2i['314159'] ] ) I'm also willing to re-architect things if there's a cleaner design. I'm new to NumPy, and I haven't written much code yet, so starting over isn't out of the question if I'm Doing It Wrong. I am going to be needing to sum all the assignment points for over a hundred students once a day, as well as run standard deviations and other stats. Plus, I'll be waiting on the results, so I'd like it to run in only a couple of seconds. Thanks in advance for any suggestions.

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• In mysql, is "explain ..." always safe?

  - by tye

  If I allow a group of users to submit "explain $whatever" to mysql (via Perl's DBI using DBD::mysql), is there anything that a user could put into $whatever that would make any database changes, leak non-trivial information, or even cause significant database load? If so, how? I know that via "explain $whatever" one can figure out what tables / columns exist (you have to guess names, though) and roughly how many records are in a table or how many records have a particular value for an indexed field. I don't expect one to be able to get any information about the contents of unindexed fields. DBD::mysql should not allow multiple statements so I don't expect it to be possible to run any query (just explain one query). Even subqueries should not be executed, just explained. But I'm not a mysql expert and there are surely features of mysql that I'm not even aware of. In trying to come up with a query plan, might the optimizer actual execute an expression in order to come up with the value that an indexed field is going to be compared against? explain select * from atable where class = somefunction(...) where atable.class is indexed and not unique and class='unused' would find no records but class='common' would find a million records. Might 'explain' evaluate somefunction(...)? And then could somefunction(...) be written such that it modifies data?

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• jQuery or CSS - How do you make a link in a table row appear underlined even when the cursor is in a

  - by adam

  I have a table of 3-4 columns, the central one being task names that are also links(yet another todo app..groan). Im trying to make it so that whenever the mouse hovers over any part of the table row - not just the link itself - the link will appear underlined. Its a small detail but its been annoying me like hell and i refuse to let it get the better of me now. At first i tried jQuery with a (forgive the obvious syntax errors but this is the jist) $('#row_in_question').hover( function(){ $(this).find(...the link..).toggleClass("highlighted") }, function(){ $(this).find(...the link..).toggleClass("highlighted") } ); with this as a styling for the a element in general .highlighted { text-decoration: underlined; } and it did indeed toggle the highlighted class on that link - however css inheritance got in the way and no visual changes made. Since i previously styled that link to have no underline when not hovered it wouldnt change the style. So how do i go about this? I dont want the whole row to become clickable, I just want the text to become underlined.

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• how does MySQL implement the "group by"?

  - by user188916

  I read from the MySQL Reference Manual and find that when it can take use of index,it just do index scan,other it will create tmp tables and do things like filesort. And I also read from other article that the "Group By" result will sort by group by columns by default,if "order by null" clause added,it won't don filesort. The difference can be found from the "explain ..." clause. so my problem is:what is the difference between "group by" clause that with "order by null" and which doesn't have? I try to use profiling to see what mysql do on the background,and only see result like: result for group clause without order by null: |preparing | 0.000016 | | Creating tmp table | 0.000048 | | executing | 0.000009 | | Copying to tmp table | 0.000109 | **| Sorting result | 0.000023 |** | Sending data | 0.000027 | result for clause with "order by null": preparing | 0.000016 | | Creating tmp table | 0.000052 | | executing | 0.000009 | | Copying to tmp table | 0.000114 | | Sending data | 0.000028 | So I guess what MySQL do when the "order by null" added,it does not use filesort algorithm,maybe when it creates the tmp table,it uses index as well,and then use the index to do group by operation,when completed,it just read result from the table rows and does not sort the result. But my original opinion is that MySQL can use quicksort to sort the items and then do group by,so the result will be sorted as well. Any opinion appreciated,thanks.

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• JAVA MySql multiple word search

  - by user1703849

  i have a database in MySql that has a name column in it which contains several words(description). I am connected to database with java through eclipse. I have a search, that returns results if only name field contains one word. id: name: info: type: 1 balloon big red balloon big 2 house expensive beautiful luxury 3 chicken wings deep fried wings tasty these are just random words but as an example my search can only see ex. balloon and then show info, but if i type chicken wings, it does nothing. so it possible somehow to search from columns with multiple words? this is my search code below import java.io.*; import java.sql.*; import java.util.*; class Search { public static void main(String[] args) { Scanner inp``ut = new Scanner(System.in); try { Connection con = DriverManager.getConnection( "jdbc:mysql://example/mydb", "user", "password"); Statement stmt = (Statement) con.createStatement(); System.out.print("enter search: "); String name = input.next(); String SQL = "SELECT * FROM menu where name LIKE '" + name + "'"; ResultSet rs = stmt.executeQuery(SQL); while (rs.next()) { System.out.println("Name: " +rs.getString("name")); System.out.println("Description: " + rs.getString("info") ); System.out.println("Price: " + rs.getString("Price")); } } catch (Exception e) { System.out.println("ERROR: " + e.getMessage()); } } }

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