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• WPF DataGrid default column types

  - by Trindaz

  Hi, I'm using a DataGrid to display 2 possible types of DataRow in a DataTable. One type has the column Parent = NULL and the other has Parent set to another DataRow in the same DataTable. The list of column in the DataTable is always different, so explicitly describing each column is not possible. I want to display a UserControl in every cell of the Parent = DataRow rows, and default Text / Check boxes for the Parent = NULL rows. My first strategy is to try and set the default Column type for all automatically generated columns to be a DataGridTemplateColumn, regardless of datatype, so that I can use styles to then use either my UserControl or CheckBox or TextBox where required. How can I do this? More importantly, though, is there a better strategy than this? Cheers, Dave

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• Trend analysis using iterative value increments

  - by Dave Jarvis

  We have configured iReport to generate the following graph: The real data points are in blue, the trend line is green. The problems include: Too many data points for the trend line Trend line does not follow a Bezier curve (spline) The source of the problem is with the incrementer class. The incrementer is provided with the data points iteratively. There does not appear to be a way to get the set of data. The code that calculates the trend line looks as follows: import java.math.BigDecimal; import net.sf.jasperreports.engine.fill.*; /** * Used by an iReport variable to increment its average. */ public class MovingAverageIncrementer implements JRIncrementer { private BigDecimal average; private int incr = 0; /** * Instantiated by the MovingAverageIncrementerFactory class. */ public MovingAverageIncrementer() { } /** * Returns the newly incremented value, which is calculated by averaging * the previous value from the previous call to this method. * * @param jrFillVariable Unused. * @param object New data point to average. * @param abstractValueProvider Unused. * @return The newly incremented value. */ public Object increment( JRFillVariable jrFillVariable, Object object, AbstractValueProvider abstractValueProvider ) { BigDecimal value = new BigDecimal( ( ( Number )object ).doubleValue() ); // Average every 10 data points // if( incr % 10 == 0 ) { setAverage( ( value.add( getAverage() ).doubleValue() / 2.0 ) ); } incr++; return getAverage(); } /** * Changes the value that is the moving average. * @param average The new moving average value. */ private void setAverage( BigDecimal average ) { this.average = average; } /** * Returns the current moving average average. * @return Value used for plotting on a report. */ protected BigDecimal getAverage() { if( this.average == null ) { this.average = new BigDecimal( 0 ); } return this.average; } /** Helper method. */ private void setAverage( double d ) { setAverage( new BigDecimal( d ) ); } } How would you create a smoother and more accurate representation of the trend line?

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• JQuery Autocomplete - format listing and only return a part to the text box

  - by Jason

  I'm using the JQuery Autocomplete and it's working just fine. I'm using it to allow someone to search for users out of a database by searching on last name or id number. Right now the drop down list that is created is the resultes of a SQL query and looks something like: $row_rst['lName'] . ', ' . $row_rst['fName'] . " - " . $row_rst['user'] . "|" . $row_rst['id'] which outputs something like: Jones, Henry - hjones Gibbons, Peter - pgibbons When I pick Henry the text box gets Jones, Henry - hjones and the hidden field gets his id. I'd like to format the drop down in columns if possible and only return Jones, Henry to the text box if possible. Are either of those options possible? I'm thinking it has to do with either formatItem(row) or formatResult(row) but I'm not sure and I can't seem to find how to go about this.

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• Hash of unique value = unique hash?

  - by Nebs

  Theoretically does hashing a unique value yield a unique value? Let's say I have a DB table with 2 columns: id and code. id is an auto-incrementing int and code is a varchar. If I do ... $code = sha1($id); ... and then store $code into the same row as $id. Will my code column be unique as well? What about if I append the current time? eg: $code = sha1($id . time()); Thanks.

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• [Cocoa] NSTableView bound to NSArrayController

  - by ndg

  Within Interface Builder I've got an NSTableView with two columns bound to a vanilla NSArrayController. The NSArrayController has its Content Array bound to an NSMutableArray in my application delegate. I've used further bindings to setup the addition and removal of rows via bindings (magic!). The issue I'm running into now is that I'd like to grab the currently selected NSTableView row and use its index to look-up the object stored in my NSArrayControllers associated array. The problem I'm running into is trying to access the NSTableView. Within my application delegate, using the following code will cause my application to crash: NSLog(@"%@", [timersTableView selectedRow]); Similarly, this also causes my application to crash: NSLog(@"%@", [timersController selectionIndex]); Given the simplicity of the code above, I must be doing something fundamentally wrong?

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• Tutorials for .NET database app using SQLite

  - by ChrisC

  I have some MS Access experience, and had a class on console c++ apps, now I am trying to develop my first program. It's a little C# db app. I have the db tables and columns planned and keyed into VS, but that's where I'm stuck. I'm needing C#/VS tutorials that will guide me on configuring relationships, datatyping, etc, on the db so I can get it ready for testing of the schema. The only tutorials I've been able to find either talk about general db basics (ie, not helping me with VS/C#), or about C# communications with an existing SQL db. Thank you. (In case it matters, I'm using the open source System.Data.SQLite (sqlite.phxsoftware.com) for the db. I chose it over SQL Server CE after seeing a comparison between the two. Also I wanted a server-less version of SQL because this little app will be on other people's computers and I want to to do as little support as possible.)

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• Select query 2-3 times faster than view

  - by Richard Knop

  This query run alone: SELECT -- lots of columns FROM (((((((((((`table1` `t1` LEFT JOIN `table2` `t2` ON(( `t2`.`userid` = `t1`.`userid` ))) LEFT JOIN `table3` `t3` ON(( `t1`.`orderid` = `t3`.`orderid` ))) LEFT JOIN `table4` `t4` ON(( `t4`.`orderitemlicenseid` = `t3`.`orderitemlicenseid` ))) LEFT JOIN `table5` `t5` ON(( `t1`.`orderid` = `t5`.`orderid` ))) LEFT JOIN `table6` `t6` ON(( `t5`.`transactionid` = `t6`.`transactionid` ))) LEFT JOIN `table7` `t7` ON(( `t7`.`transactionid` = `t5`.`transactionid` ))) LEFT JOIN `table8` `t8` ON(( `t8`.`voucherid` = `t7`.`voucherid` ))) LEFT JOIN `table9` `t9` ON(( `t8`.`voucherid` = `t9`.`voucherid` ))) LEFT JOIN `table10` `t10` ON(( ( `t10`.`vouchergroupid` = `t9`.`vouchergroupid` ) AND ( `t2`.`territoryid` = `t10`.`territoryid` ) ))) LEFT JOIN `table11` `t11` ON(( `t11`.`voucherid` = `t8`.`voucherid` ))) LEFT JOIN `table12` `t12` ON(( `t12`.`orderid` = `t1`.`orderid` ))) GROUP BY `t5`.`transactionid` Takes about 2.5 seconds to finish. When I save it to a view and run it as: SELECT * FROM viewName; It takes 7 seconds to finish. What is the reason and how can I make the view faster?

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• Maths Question: number of different permutations

  - by KingCong

  This is more of a maths question than programming but I figure a lot of people here are pretty good at maths! :) My question is: Given a 9 x 9 grid (81 cells) that must contain the numbers 1 to 9 each exactly 9 times, how many different grids can be produced. The order of the numbers doesn't matter, for example the first row could contain nine 1's etc. This is related to Sudoku and we know the number of valid Sudoku grids is 6.67×10^21, so since my problem isn't constrained like Sudoku by having to have each of the 9 numbers in each row, column and box then the answer should be greater than 6.67×10^21. My first thought was that the answer is 81! however on further reflection this assume that the 81 number possible for each cell are different, distinct number. They are not, there are 81 possible numbers for each cell but only 9 possible different numbers. My next thought was then that each of the cells in the first row can be any number between 1 and 9. If by chance the first row happened to be all the same number, say all 1s, then each cell in the second row could only have 8 possibilites, 2-9. If this continued down until the last row then number of different permutations could be calculated by 9^2 * 8^2 * 7^2 ..... * 1^2. However this doesn't work if each row doesn't contain 9 of the same number. It's been quite a while since I studied this stuff and I can't think of a way to work it out, I'd appreciate any help anyone can offer.

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• grouping data from two dataset

  - by Garcia Julien

  hi, i've got a problem with dataset: I've got two dataset from two different server but they have the same columns. so it's like that: First DataSet : asset description make jobtype jan feb ... dec 0001 mine ik Acc 0 0 10 0002 yours ic Over 0 0 10 Second dataset : asset description make jobtype jan feb ... dec 0001 mine ik Acc 10 0 10 0002 yours ic Gen 0 0 0 But i would like to merge the 2 dataset into one like that: asset description make jobtype lhjan imjan lhfeb lhfeb ... lhdec imdec 0001 mine ik Acc 0 10 0 0 10 10 0002 yours ic Over 0 0 0 0 10 0 so all the data from one is combine with the second with the same asset and the same jobtype. I try linq but i can't arrive to make it like i want. I'm working on vb.net framework 3.5. could you help me? Julien

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• how to do this in shell

  - by user150674

  I have a very large file, named 'ColCheckMe', tab-delimited, that you are asked to process. You are told that each line in 'ColCheckMe' has 7 columns, and that the values in the 5th column are integers. Using shell functions indicate how you would verify that these conditions are satisfied in 'ColCheckMe' if In the same file, each value in column 1 is unique. How would I verify that? Also how to write a shell function that counts the number of occurrences of the word “SpecStr” in the file 'ColCheckMe' I tried the first part which checks for the valid number of field and checks the 5th field being integer field. nawk ' NF != 7 { printf("[%d] has invalid [%d] number of fields\n", FNR, NF) } $5 !~ /^[0-9]+$/ { printf("[%d] 5th field is invalid [%s]\n", FNR, $5) }' ColCheckMe now i wanna verify in the same file if the value in column 1 is unique. Also is there a way to write a shell function to count the occurrences of the world "SpecStr" in the file 'ColCheckMe' Thanks a lot

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• MDX equivalent to SQL subqueries with aggregation

  - by James Lampe

  I'm new to MDX and trying to solve the following problem. Investigated calculated members, subselects, scope statements, etc but can't quite get it to do what I want. Let's say I'm trying to come up with the MDX equivalent to the following SQL query: SELECT SUM(netMarketValue) net, SUM(CASE WHEN netMarketValue > 0 THEN netMarketValue ELSE 0 END) assets, SUM(CASE WHEN netMarketValue < 0 THEN netMarketValue ELSE 0 END) liabilities, SUM(ABS(netMarketValue)) gross someEntity1 FROM ( SELECT SUM(marketValue) netMarketValue, someEntity1, someEntity2 FROM <some set of tables> GROUP BY someEntity1, someEntity2) t GROUP BY someEntity1 In other words, I have an account ledger where I hide internal offsetting transactions (within someEntity2), then calculate assets & liabilities after aggregating them by someEntity2. Then I want to see the grand total of those assets & liabilities aggregated by the bigger entity, someEntity1. In my MDX schema I'd presumably have a cube with dimensions for someEntity1 & someEntity2, and marketValue would be my fact table/measure. I suppose i could create another DSV that did what my subquery does (calculating net), and simply create a cube with that as my measure dimension, but I wonder if there is a better way. I'd rather not have 2 cubes (one for these net calculations and another to go to a lower level of granularity for other use cases), since it will be a lot of duplicate info in my database. These will be very large cubes.

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• What is so bad about using SQL INNER JOIN

  - by Stephen B. Burris Jr.

  Everytime a database diagram gets looked out, one area people are critical of is inner joins. They look at them hard and has questions to see if an inner join really needs to be there. Simple Library Example: A many-to-many relationship is normally defined in SQL with three tables: Book, Category, BookCategory. In this situation, Category is a table that contains two columns: ID, CategoryName. In this situation, I have gotten questions about the Category table, is it need? Can it be used as a lookup table, and in the BookCategory table store the CategoryName instead of the CategoryID to stop from having to do an additional INNER JOIN. (For this question, we are going to ignore the changing, deleting of any CategoryNames) The question is, what is so bad about inner joins? At what point is doing them a negative thing (general guidelines like # of transactions, # of records, # of joins in a statement, etc)?

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• How to Pass parameter to SQlDataSource from gridview?

  - by user144842

  Gridview has many columns and a Delete button as well. Delete button is a control as TemplateField <asp:TemplateField> <ItemTemplate> <asp:LinkButton ID="btnDelete" CommandName="Delete" Text='<%# Eval("disabled").ToString()=="False" ? "Disabled" : "Enabled" %>' OnClientClick="return confirm('Are you sure you want to take this action?');" runat="server"></asp:LinkButton> </ItemTemplate> </asp:TemplateField> Now associated SQLDataSource's Delete command's stored procedure is expecting two parameters. One is going from DataKeyNames (RowID), other one i wanna pass is the Text of btnDelete (True or False). How can i achieve it?

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• Foreign key onto weak entity set in MS SQL Server 2008?

  - by Nic Waller

  I'm using Microsoft SQL Server 2008 Management Studio to create a relational schema by following an Entity-Relationship diagram. (included below; unrelated details removed) Until now, primary and foreign keys have been working as expected. But when I try to create a foreign key from the entity relationship takes onto the weak entity set section, I get an error. Section is identified by a composite primary key in the context of course, which has course_id as a primary key. Therefore, the primary key of section is a 4-way composite key. The entity relationship takes needs to refer to section, so it includes all 4 primary attributes from section in it's own primary key. When trying to establish a foreign key relationship from takes to section, Studio gives the following error: The columns in table 'section' do not match an existing primary key or UNIQUE constraint. Am I doing something wrong, or is this an unsupported configuration? I can provide more details or the SQL schema if necessary.

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• Database structure - To join or not to join

  - by Industrial

  Hi! We're drawing up the database structure with the help of mySQL Workbench for a new app and the number of joins required to make a listing of the data is increasing drastically as the many-to-many relationships increases. The application will be quite read-heavy and have a couple of hundred thousand rows per table. The questions: Is it really that bad to merge tables where needed and thereby reducing joins? Should we start looking at horizontal partitioning? (in conjunction with merging tables) Is there a better way then pivot tables to take care of many-to-many relationships? We discussed about instead storing all data in serialized text columns and having the application make the sorting instead of the database, but this seems like a very bad idea, even though that the database will be heavily cached. What do you think? Thanks!

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• DataBinding to ListView

  - by Neir0

  Hi, I have a class public class Foo { public List<string> list1 { get; set;} public List<string> list2 { get; set; } public string url; } and a ListView with two columns <ListView Name="listview" ItemsSource="{Binding}"> <ListView.View> <GridView> <GridViewColumn Header="list1" DisplayMemberBinding="{Binding Path=list1}" /> <GridViewColumn Header="list2" DisplayMemberBinding="{Binding Path=list2}" /> </GridView> </ListView.View> </ListView> How i can to bind instance of Foo class to ListView? Here i set DataContext listview.DataContext = new Foo() { list1 = new[] { "dsfasd", "asdfasdf", "asdf", "asdfasd" }.ToList(), list2 = new[] { "dsfasd", "asdfasdf", "asdf", "asdfasd" }.ToList() }; But it's not work.

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• SPGridView current item in Sharepoint

  - by pistacchio

  Hi, I'm making a custom webpart. I takes some items from a list and display them with a SPGridView. I bound the fields like this: // Grab data from a SP List into dvwTickets SPGridView grdMyTickets = new SPGridView(); grdMyTickets.DataSource = dvwTickets; [..] BoundField colTicketTypology = new BoundField(); colTicketTypology.DataField = "ID"; colTicketTypology.HeaderText = ticketList.Fields.GetFieldByInternalName("ID").Title; grdMyTickets.Columns.Add(colTicketTypology); [..] This works. Now, what a grid does behind the scene when binding data to it is cycling through the binded data. How can I access the "Current Item" to make operations on each item while binding? Thanks

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• SP Gridview link button column not working

  - by Dilse Naaz

  Hi I have one sharepoint custom page application which is rendering from a user control. In the user control page, i had used SPGridview for displaying data. My first column is Title Column (link button column), when the user click on the link, then one popup window will open with corresponding data. But the problem is the link button is not working properly. But this application is working as fine in asp.net application. My code is shown below.. <asp:UpdatePanel runat="server" ID="UpdatePanel2"> <ContentTemplate> <SharePoint:SPGridView ID="dgApplicationBox" CellPadding="0" Height="100%" runat="server" ForeColor="Black" Font-Size="10px" Font-Names="Verdana" AutoGenerateColumns="False" AllowPaging="True" Width="100%" BorderStyle="None" BorderWidth="0px" PageSize="10" BorderColor="White" BackColor="White" OnRowDataBound="dgApplicationBox_RowDataBound" DataKeyNames="ApplicationID" OnSelectedIndexChanged="dgApplicationBox_SelectedIndexChanged" OnPageIndexChanging="dgApplicationBox_PageIndexChanging" CssClass="ms-listviewtable" AlternatingRowStyle-CssClass="ms-alternating"> <SelectedRowStyle Font-Bold="True" ForeColor="Black" BackColor="#CE5D5A"></SelectedRowStyle> <EditRowStyle Font-Size="10px" Font-Names="Verdana,Arial,Helvetica,sans-serif"></EditRowStyle> <HeaderStyle Font-Size="11px" Height="20px" Font-Bold="True" ForeColor="Black" BackColor="#E7E8EC"> </HeaderStyle> <PagerStyle HorizontalAlign="Center" ForeColor="#414E61" Font-Size="5px" Font-Names="arial" Height="10px" BackColor="#EBF3FF"></PagerStyle> <RowStyle /> <Columns> <asp:TemplateField HeaderText="Title" HeaderStyle-CssClass="ms-vb"> <ItemTemplate> <asp:LinkButton ID="lbtnSubject" Text='<%# Bind("UDF5") %>' runat="server" OnClick="lbtnSubject_Click"></asp:LinkButton> </ItemTemplate> <HeaderStyle HorizontalAlign="Left" CssClass="ms-vh2" Font-Bold="true" /> <ItemStyle HorizontalAlign="Left" CssClass="ms-vb2" /> </asp:TemplateField> <asp:TemplateField HeaderText="Request No."> <ItemTemplate> <asp:Label ID="lblReqNo" Text='<%# Bind("UDF1") %>' runat="server" /> </ItemTemplate> <HeaderStyle HorizontalAlign="Left" CssClass="ms-vh2" Font-Bold="true" /> <ItemStyle HorizontalAlign="Left" CssClass="ms-vb2" /> </asp:TemplateField> <asp:BoundField DataField="CreatedOn" HeaderText="Created On" DataFormatString="{0:MM/dd/yyyy}" HeaderStyle-HorizontalAlign="Left" ItemStyle-HorizontalAlign="Left"> <HeaderStyle CssClass="ms-vh2" Font-Bold="true"></HeaderStyle> <ItemStyle CssClass="ms-vb2"></ItemStyle> </asp:BoundField> <asp:BoundField DataField="Name" HeaderText="Form Type" HeaderStyle-HorizontalAlign="Left" ItemStyle-HorizontalAlign="Left"> <HeaderStyle CssClass="ms-vh2" Font-Bold="true"></HeaderStyle> <ItemStyle CssClass="ms-vb2"></ItemStyle> </asp:BoundField> <asp:TemplateField HeaderText="History"> <HeaderStyle CssClass="ms-vh2" Font-Bold="true"></HeaderStyle> <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" Width="21px" CssClass="ms-vb2"> </ItemStyle> <ItemTemplate> <asp:LinkButton ID="lbtnView" runat="server" OnClick="lbtnView_Click" >View</asp:LinkButton> </ItemTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Application Id" Visible="False"> <ItemTemplate> <asp:Label ID="lblApplicationId" runat="server" Text='<%# Bind("ApplicationId") %>'></asp:Label> </ItemTemplate> <HeaderStyle HorizontalAlign="Left" CssClass="ms-vh2" Font-Bold="true" /> <ItemStyle HorizontalAlign="Left" CssClass="ms-vb2" /> </asp:TemplateField> </Columns> </SharePoint:SPGridView> </ContentTemplate> </asp:UpdatePanel> when the user click on the link button, this code will works.. try { clearSession(); Session["DigitalSignature"] = null; Button btnDetails = sender as Button; DataTable dt = (DataTable)dgApplicationBox.DataSource; GridViewRow gvRow = (GridViewRow)(sender as LinkButton).Parent.Parent; Session["AppId"] = ((Label)gvRow.FindControl("lblApplicationId")).Text; string subject = ((LinkButton)gvRow.FindControl("lbtnSubject")).Text; WFInfo objWFInfo = new WFInfo(); objWFInfo.InitWorkflowProperty(Convert.ToInt32(Session["AppId"].ToString()), Session["CurrentUser"].ToString()); Session["FormId"] = objWFInfo.FormID.ToString(); string strFilname = objWFInfo.GetFormName(objWFInfo.ApplicationCategoryID.ToString()); string WindowName = strFilname; strFilname += ".aspx"; Session["CategoryId"] = objWFInfo.ApplicationCategoryID.ToString(); //pnlSubmitModal_ModalPopupExtender.Show(); ScriptManager.RegisterStartupScript(this, this.GetType(), "starScript", "popUpWindow('" + strFilname + "?tittle=" + subject + "', 800, 690,'" + WindowName + "');", true); this.Controls.Add(new LiteralControl("<script>alert('hi');</script>")); if (Session["CurrentUser"] != null) { ApplicationForm objApplication = new ApplicationForm(); objApplication.markRead(Convert.ToInt32(Session["AppId"].ToString()), Session["CurrentUser"].ToString()); } bindFolderData(); } If i click on the link button, there will be only post back occuring. but not the popup window open.. Please help me for resolving this problem. thanks in advance..

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• iPhone - dequeueReusableCellWithIdentifier usage

  - by Jukurrpa

  Hi, I'm working on a iPhone app which has a pretty large UITableView with data taken from the web, so I'm trying to optimize its creation and usage. I found out that dequeueReusableCellWithIdentifier is pretty useful, but after seeing many source codes using this, I'm wondering if the usage I make of this function is the good one. Here is what people usually do: UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:@"Cell"]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:@"Cell"]; // Add elements to the cell return cell; And here is the way I did it: NSString identifier = [NSString stringWithFormat:@"Cell @d", indexPath.row]: // The cell row UITableViewCell* cell = [tableView dequeueReusableCellWithIdentifier:identifier]; if (cell != nil) return cell; cell = [[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:identifier]; // Add elements to the cell return cell; The difference is that people use the same identifier for every cell, so dequeuing one only avoids to alloc a new one. For me, the point of queuing was to give each cell a unique identifier, so when the app asks for a cell it already displayed, neither allocation nor element adding have to be done. In fine I don't know which is best, the "common" method ceils the table's memory usage to the exact number of cells it display, whislt the method I use seems to favor speed as it keeps all calculated cells, but can cause large memory consumption (unless there's an inner limit to the queue). Am I wrong to use it this way? Or is it just up to the developper, depending on his needs?

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• Cleanest RESTful design for purely "action" calls?

  - by Josh Handel

  Hello all, I am sticking my toe in the RESTful waters and I just can't find a "satisfactory" solution to how to handle truely "action" oriented calls on a RESTful service? My quandry can be broken down into two parts. 1) Transactional calls: I understand the idea of having an ActionTransactor that you get a resource too with a post, update the parameters and then commit with a PUT (as described all over the place and in the Orilly RESTful Web services book).. But I struggle with the idea of keeping URLs with states present for ever.. If we really honestly don't need to keep a transaction for ever can we kill the resource URI? do URIs need to be perminate or can they be transiant URIs that expire 2) Non transactional calls: these might be calls to perform some workflow that spans multiple resources but having a resource just doesn't make since.. An example might be to re-generating some calculated ans cached value like a large aggreget or re-indexing blog or some such "purely" action. Anyways, I'm curious about the communities thoughts on this... Thus far, I've read that Overloading Post is the cleanest way to handle part 2.. But there is an equal amount of argument against that approach as well. And (to me) its not self documenting which I though was one of the key design goals of RESTful APIs.

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• Does replace into have a where clause?

  - by Lajos Arpad

  I'm writing an application and I'm using MySQL as DBMS, we are downloading property offers and there were some performance issues. The old architecture looked like this: A property is updated. If the number of affected rows is not 1, then the update is not considered successful, elseway the update query solves our problem. If the update was not successful, and the number of affected rows is more than 1, we have duplicates and we delete all of them. After we deleted duplicates if needed if the update was not successful, an insert happens. This architecture was working well, but there were some speed issues, because properties are deleted if they were not updated for 15 days. Theoretically the main problem is deleting properties, because some properties are alive for months and the indexes are very far from each other (we are talking about 500, 000+ properties). Our host told me to use replace into instead of deleting properties and all deprecated properties should be considered as DEAD. I've done this, but problems started to occur because of syntax error and I couldn't find anywhere an example of replace into with a where clause (I'd like to replace a DEAD property with the new property instead of deleting the old property and insert a new to assure optimization). My query looked like this: replace into table_name(column1, ..., columnn) values(value1, ..., valuen) where ID = idValue Of course, I've calculated idValue and handled everything but I had a syntax error. I would like to know if I'm wrong and there is a where clause for replace into. I've found an alternative solution, which is even better than replace into (using simply an update query) because deletes are happening behind the curtains if I use replace into, but I would like to know if I'm wrong when I say that replace into doesn't have a where clause. For more reference, see this link: http://dev.mysql.com/doc/refman/5.0/en/replace.html Thank you for your answers in advance, Lajos Árpád

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• best way to store 1:1 user relationships in relational database

  - by aharon

  What is the best way to store user relationships, e.g. friendships, that must be bidirectional (you're my friend, thus I'm your friend) in a rel. database, e.g. MYSql? I can think of two ways: Everytime a user friends another user, I'd add two rows to a database, row A consisting of the user id of the innitiating user followed by the UID of the accepting user in the next column. Row B would be the reverse. You'd only add one row, UID(initiating user) followed by UID(accepting user); and then just search through both columns when trying to figure out whether user 1 is a friend of user 2. Surely there is something better?

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• Convert a Mysql database from latin to UTF-8

  - by Matthieu

  I am converting a website from ISO to UTF-8, so I need to convert the Mysql database too. On internet, I read various solutions, I don't know wich one to choose. Do I really need to convert my varchar columns to binary, then to utf8 like that : ALTER TABLE t MODIFY col BINARY(150); ALTER TABLE t MODIFY col CHAR(150) CHARACTER SET utf8; This is long to do that for each column, of each table, of each database. I have 10 database, wich 20 tables each, wich around 2 - 3 varchar colums (2 queries each column), this gives me around 1000 queries to write ! How come ? How to do ?

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• Lost Update Anomaly in Sql Server Update Command

  - by Javed

  Hi, I am very much confused. I have a transaction in ReadCommitted Isolation level. Among other things I am also updating a counter value in it, something similar to below: Update tblCount set counter = counter + 1 My application is a desktop application and this transaction happens to occur quite frequently and concurrently. We recently noticed an error that sometimes the counter value doesn't get updated or is missed. We also insert one record on each counter update so we are sure that records have been inserted but somehow counter fails to update. This happens once in 2000 simulaneous transactions. I seriously doubt it is a lost update anomaly I am facing but if you look at the command above, it's just update the counter from its own value: if I have started a transaction and the transaction has reached this statement, it should have locked the row. This should not cause lost update, but it's happening somehow. Is the thing that this update command works in two parts? Like first it reads the counter value (during which it doesn't get the exclusive lock) and then writes the new calculated value (when it does get an exclusive lock)? Please help, I have got really confused.

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• Ordered many-to-many relationship in NHibernate

  - by Kristoffer

  Let's say I have two classes: Item and ItemCollection, where ItemCollection contains an ordered list of Item objects with an index, i.e. the list is ordered in a way specified by the user. Let's also say that they have a many-to-many relationship, an ItemCollection can contain many items and an Item can belong to several ItemCollections. That would, in my head, require three tables in the database. One for Item, one for ItemCollection and one for the ordered mapping. The mapping table would contain three columns: int ItemID int ItemCollectionID int ListIndex QUESTION: How would you design the ItemCollection class? Should the list of Item objects be a list, dictionary or other? What would the NHibernate mapping look like to get the ListIndex into the picture?

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