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  • Pinterest Gridview implementation on iOS

    - by Amal
    I want to implement a grid view like the one in Pinterest I thought about implementing as 3 table views. But I was not able to scroll them together well. When I implemented the scrollViewDidScroll and set the contentOffset for the table views other the scrollView , the scrolling became slow and unusable. Another implementation I did was of was having a set of images to load and calling the viewDraw function in scrollViewDidScroll. THe ViewDraw function just draws the necessary images and removes the rest of the images from the memory which were already drawn but wont be visible . this too makes the ScrollView Scrolling slow. And another issue with it is that there are white(background color) patches before the images are drawn. What should be the best way to implement this grid view ?

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  • Show them the default, and allow them to press escape or Ctrl-Z

    - by cf_PhillipSenn
    I have a table cell, and when the user clicks on it, I replace the contents of the table cell with an input tag with the current contents as the default. But I don't like it's behavior because there's a chance that the user can delete the contexts on the input simply by clicking on it a second time. $('.LastName').live('click', function() { var myText = $(this).text(); $(this).empty().append('<input name="LastName" id="LastName" value="' + myText + '" />'); document.myForm.LastName.focus(); }); Q: How do I give the user a default, plus allow them to press the escape key or Ctrl-Z while in the middle of an edit?

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  • Nhibernate multilevel hierarchy save error?

    - by nisbus
    Hi, I have a database with a 6 level hierarchy and a domain model on top of that. something like this: Category -SubCategory -Container -DataDescription | Meta data -Data The mapping I'm using follows the following pattern: <class name="Category, Sample" table="Categories"> <id name="Id" column="Id" type="System.Int32" unsaved-value="0"> <generator class="native"/> </id> <property name="Name" access="property" type="String" column="Name"/> <property name="Metadata" access="property" type="String" column="Metadata"/> <bag name="SubCategories" cascade="save-update" lazy="true" inverse="true"> <key column="Id" foreign-key="category_subCategory_fk"/> <one-to-many class="SubCategory, Sample" /> </bag> </class> <class name="SubCategory, Sample" table="SubCategories"> <id name="Id" column="Id" type="System.Int32" unsaved-value="0"> <generator class="native"/> </id> <many-to-one name="Category" class="Category, Sample" foreign-key="subCat_category_fk"/> <property name="Name" access="property" type="String"/> <property name="Metadata" access="property" type="String"/> <bag name="Containers" inverse="true" cascade="save-update" lazy="true"> <key column="Id" foreign-key="subCat_container_fk" /> <one-to-many class="Container, Sample" /> </bag> </class> <class name="Container, Sample" table="Containers"> <id name="Id" column="Id" type="System.Int32" unsaved-value="0"> <generator class="assigned"/> </id> <many-to-one name="SubCategory" class="SubCategory,Sample" foreign-key="container_subCat_fk"/> <property name="Name" access="property" type="String" column="Name"/> <bag name="DataDescription" cascade="all" lazy="true" inverse="true"> <key column="Id" foreign-key="container_ DataDescription_fk"/> <one-to-many class="DataDescription, Sample" /> </bag> <bag name="MetaData" cascade="all" lazy="true" inverse="true"> <key column="Id" foreign-key="container_metadata_cat_fk"/> <one-to-many class="MetaData, Sample" /> </bag> </class> For some reason when I try to save the category (with the subcategory, container etc. attached) I get a foreign key violation from the database. The code is something like this (Pseudo). var category = new Category(); var subCategory = new SubCategory(); var container = new Container(); var dataDescription = new DataDescription(); var metaData = new MetaData(); category.AddSubCategory(subCategory); subCategory.AddContainer(container); container.AddDataDescription(dataDescription); container.AddMetaData(metaData); Session.Save(category); Here is the log from this test : DEBUG NHibernate.SQL - INSERT INTO Categories (Name, Metadata) VALUES (@p0, @p1); select SCOPE_IDENTITY(); @p0 = 'Unit test', @p1 = 'unit test' DEBUG NHibernate.SQL - INSERT INTO SubCategories (Category, Name, Metadata) VALUES (@p0, @p1, @p2); select SCOPE_IDENTITY(); @p0 = '1', @p1 = 'Unit test', @p2 = 'unit test' DEBUG NHibernate.SQL - INSERT INTO Containers (SubCategory, Name, Frequency, Scale, Measurement, Currency, Metadata, Id) VALUES (@p0, @p1, @p2, @p3, @p4, @p5, @p6, @p7); @p0 = '1', @p1 = 'Unit test', @p2 = '15', @p3 = '1', @p4 = '1', @p5 = '1', @p6 = 'unit test', @p7 = '0' ERROR NHibernate.Util.ADOExceptionReporter - The INSERT statement conflicted with the FOREIGN KEY constraint "subCat_container_fk". The conflict occurred in database "Sample", table "dbo.SubCategories", column 'Id'. The methods for adding items to objects is always as follows: public void AddSubCategory(ISubCategory subCategory) { subCategory.Category = this; SubCategories.Add(subCategory); } What am I missing?? Thanks, nisbus

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  • current_date casting

    - by Armen Mkrtchyan
    Hi. string selectSql = "update " + table + " set state_" + mode + "_id=1 WHERE stoping_" + mode + " < current_date;"; when i call current_date, it return yyyy-MM-dd format, but i want to return dd.MM.yyyy format, how can i do that. please help. my program works fine when i am trying string selectSql = "update " + table + " set state_" + mode + "_id=1 WHERE stoping_" + mode + " < '16.04.2010';";

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  • Alert on gridview edit based on permission

    - by Vicky
    I have a gridview with edit option at the start of the row. Also I maintain a seperate table called Permission where I maintain user permissions. I have three different types of permissions like Admin, Leads, Programmers. These all three will have access to the gridview. Except admin if anyone tries to edit the gridview on clicking the edit option, I need to give an alert like This row has important validation and make sure you make proper changes. When I edit, the action with happen on table called Application. The table has a column called Comments. Also the alert should happen only when they try to edit rows where the Comments column have these values in them. ManLog datas Funding Approved Exported Applications My try so far. public bool IsApplicationUser(string userName) { return CheckUser(userName); } public static bool CheckUser(string userName) { string CS = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString(); DataTable dt = new DataTable(); using (SqlConnection connection = new SqlConnection(CS)) { SqlCommand command = new SqlCommand(); command.Connection = connection; string strquery = "select * from Permissions where AppCode='Nest' and UserID = '" + userName + "'"; SqlCommand cmd = new SqlCommand(strquery, connection); SqlDataAdapter da = new SqlDataAdapter(cmd); da.Fill(dt); } if (dt.Rows.Count >= 1) return true; else return true; } protected void Details_RowCommand(object sender, GridViewCommandEventArgs e) { string currentUser = HttpContext.Current.Request.LogonUserIdentity.Name; string str = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString(); string[] words = currentUser.Split('\\'); currentUser = words[1]; bool appuser = IsApplicationUser(currentUser); if (appuser) { DataSet ds = new DataSet(); using (SqlConnection connection = new SqlConnection(str)) { SqlCommand command = new SqlCommand(); command.Connection = connection; string strquery = "select Role_Cd from User_Role where AppCode='PM' and UserID = '" + currentUser + "'"; SqlCommand cmd = new SqlCommand(strquery, connection); SqlDataAdapter da = new SqlDataAdapter(cmd); da.Fill(ds); } if (e.CommandName.Equals("Edit") && ds.Tables[0].Rows[0]["Role_Cd"].ToString().Trim() != "ADMIN") { int index = Convert.ToInt32(e.CommandArgument); GridView gvCurrentGrid = (GridView)sender; GridViewRow row = gvCurrentGrid.Rows[index]; string strID = ((Label)row.FindControl("lblID")).Text; string strAppName = ((Label)row.FindControl("lblAppName")).Text; Response.Redirect("AddApplication.aspx?ID=" + strID + "&AppName=" + strAppName + "&Edit=True"); } } } Kindly let me know if I need to add something. Thanks for any suggestions.

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  • Array within Form collecting multiple values with the same name possible?

    - by JM4
    Good afternoon, I will first start with the goal I am trying to accomplish and then give a very basic sample of what I need to do. Goal Instead of collecting several variables and naming them with keys individually, I have decided to give in and use an array structure to handle all inputs of the same type and rules. Once I have the variables, I will validate against them and if 'ok' store them in a MySQL table. The table will hold consumer information and will need to store multiple rows of the same type of information. First Pass I will leave out the validation portion of this question because I feel I need to first understand the basics. <form action="?" method="POST" name="Form"> Member 1 First Name:<input type="text" name="MemberFirstName[]" /><br /> Member 1 Last Name: <input type="text" name="MemberLastName[]" /><br /> Member 1 Email: <input type="text" name="MemberEmail[]" /><br /> Member 2 First Name:<input type="text" name="MemberFirstName[]" /><br /> Member 2 Last Name: <input type="text" name="MemberLastName[]" /><br /> Member 2 Email: <input type="text" name="MemberEmail[]" /><br /> Member 3 First Name:<input type="text" name="MemberFirstName[]" /><br /> Member 3 Last Name: <input type="text" name="MemberLastName[]" /><br /> Member 3 Email: <input type="text" name="MemberEmail[]" /><br /> <input type="submit" name="submit" value="Continue" /> </form> I am hoping that each input given for First Name (a required field) will generate a unique key for that particular entry and not overwrite any data entered. Because I am carrying information from page to page (checkout form), I am turning the POST variables into SESSION variables then storing in a mysql database in the end. My hope is to have: <?php $conn = mysql_connect("localhost", "username", "password"); mysql_select_db("DBname",$conn); $sql = "INSERT INTO tablename VALUES ('$_SESSION[Member1FirstName]', '$_SESSION[Member1LastName]', '$_SESSION[Member1Email]', '$_SESSION[Member2FirstName]', '$_SESSION[Member2LastName]', '$_SESSION[Member2Email]', '$_SESSION[Member1FirstName]', '$_SESSION[Member3LastName]', '$_SESSION[Member3Email]')"; $result = mysql_query($sql, $conn) or die(mysql_error()); Header ("Location: completed.php"); ?> Where Member1, Member2, and Member3 values will appear on their own row within the table. I KNOW my code is wrong but I am giving a first shot at the overall business purpose I am trying to achieve and trying to learn how to code the right way. I am very, very new to programming so any 'baby advice' is greatly appreciated.

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  • Need to map classes to different databases at runtime in Hibernate

    - by serg555
    I have MainDB database and unknown number (at compile time) of UserDB_1, ..., UserDB_N databases. MainDB contains names of those UserDB databases in some table (new UserDB can be created at runtime). All UserDB have exactly the same table names and fields. How to handle such situation in Hibernate? (database structure cannot be changed). Currently I am planning to create generic User classes not mapped to anything and just use native SQL for all queries: session.createSQLQuery("select * from " + db + ".user where id=1") .setResultTransformer(Transformers.aliasToBean(User.class)); Is there anything better I can do? Ideally I would want to have mappings for UserDB tables and relations and use HQL on required database.

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  • problem with select boxes - second options based on first selection

    - by Charles Marsh
    Hello All, I just posted a question about opening in a new window but if I use window.location it doesn't work?? is there a problem with my javascript? <script type="text/javascript"> function setOptions(chosen){ var selbox = document.formName.table; selbox.options.length = 0; if (chosen == " ") { selbox.options[selbox.options.length] = new Option('No diploma selected',' '); } if (chosen == "1") { selbox.options[selbox.options.length] = new Option('first choice - option one','http://www.pitman-training.com'); selbox.options[selbox.options.length] = new Option('first choice - option two','onetwo'); } if (chosen == "2") { selbox.options[selbox.options.length] = new Option('second choice - option one','twoone'); selbox.options[selbox.options.length] = new Option('second choice - option two','twotwo'); selbox.options[selbox.options.length] = new Option('second choice - option three','twothree'); selbox.options[selbox.options.length] = new Option('second choice - option four','twofour'); } if (chosen == "3") { selbox.options[selbox.options.length] = new Option('third choice - option one','threeone'); selbox.options[selbox.options.length] = new Option('third choice - option two','threetwo'); } } </script> Its a little messy I know... <form name="formName" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>"> <select name="optone" size="1" onchange="setOptions(document.formName.optone.options[document.formName.optone.selectedIndex].value);"> <option value=" " selected="selected">Please select a diploma</option> <option value="1">First Choice</option> <option value="2">Second Choice</option> <option value="3">Third Choice</option> </select> <select name="table" size="1" > <option value=" " selected="selected">No diploma selected</option> </select> <input type="submit" onclick="ob=this.form.table;window.location(ob.options[ob.selectedIndex].value)"/> </form> to be honest I'm not happy with this anyway I want a way to hide the Submit button until the second selected box has been selected...but I'm no java expert! Can anyone point me in the right direction?

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  • Custom editor in QAbstractTableModel

    - by Martin Beckett
    Does anyone have an example of using a QWidget as an editor in a QAbstractTableModel? I have a column which when edited should create a QCombobox with the list of choices. The docs seem to suggest I need to write a QAbstractItemDelegate and a custom paint function but that seems overkill to simply pop-up a standard QCombobox in Qt::EditRole. Note - the combo box contents are the same for every row and it only needs to be shown when somebody clicks in the cell. I know this should be simple but I can't get it to work. It's easy for a QTableWidget based table - but I need it for a very large data table.

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  • How to retrieve Aggregate objects?

    - by Jebb
    In DDD, Repository takes care of saving and retrieving domain objects and also serves as collection of Aggregate Roots. My question is how do you retrieve the information for those child entities (let's say from DB) of an Aggregate where basic rule is Repository should just hold collection of Aggregate Roots (parent object) and not child objects? For example: User (parent object) Orders (child object) User domain object is stored in user table and Orders are stored in another table. Basically, retrieving a Domain Object could be like this: <?php $userRepos = new UserRepository(); $user = $userRepos->find($userId); ?> How then the child object (Orders) of User entity be retrieve to be as part of the User aggregate?

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  • Problem writing HTML content to Word document in ASP.NET

    - by saran
    I am trying to export the HTML page contents to Word. My Html display page is: What is your favourite color? NA List the top three school ? one National two Devs three PS And a button for click event. The button click event will open MS word and paste the page contents in word. The word page contains the table property of html design page. It occurs only in Word 2003. But in word 2007 the word document contains the text with out table property. How can I remove this table property in word 2003. I am not able to add the snapshots. Else i will make you clear. I am designing the web page by aspx. I am exporting the web page content by the following code. protected void Button1_Click(object sender, EventArgs e) { Response.ContentEncoding = System.Text.Encoding.UTF7; System.Text.StringBuilder SB = new System.Text.StringBuilder(); System.IO.StringWriter SW = new System.IO.StringWriter(); System.Web.UI.HtmlTextWriter htmlTW = new System.Web.UI.HtmlTextWriter(SW); tbl.RenderControl(htmlTW); string strBody = "<html>" + "<body>" + "<div><b>" + htmlTW.InnerWriter.ToString() + "</b></div>" + "</body>" + "</html>"; Response.AppendHeader("Content-Type", "application/msword"); Response.AppendHeader("Content-disposition", "attachment; filename=" + fileName); Response.ContentEncoding = System.Text.Encoding.UTF7; string fileName1 = "C://Temp/Excel" + DateTime.Now.Millisecond.ToString(); BinaryWriter writer = new BinaryWriter(File.Open(fileName1, FileMode.Create)); writer.Write(strBody); writer.Close(); FileStream fs = new FileStream(fileName1, FileMode.Open, FileAccess.Read); byte[] renderedBytes; // Create a byte array of file stream length renderedBytes = new byte[fs.Length]; //Read block of bytes from stream into the byte array fs.Read(renderedBytes, 0, System.Convert.ToInt32(fs.Length)); //Close the File Stream fs.Close(); FileInfo TheFile = new FileInfo(fileName1); if (TheFile.Exists) { File.Delete(fileName1); } Response.BinaryWrite(renderedBytes); Response.Flush(); Response.End(); }

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  • Add blank cell at end of UITable

    - by Michael
    I'm trying to add an additional cell for custom content as the last cell in a tableView, without altering the dictionary that creates the other content of the table. I think the place to add it is in cellForRowAtIndexPath rather than adding one to the numberOfRowsInSection, which just crashes if I do. I get a cellCount from the dictionary that creates the data for the table, then in cellForRowAtIndexPath, I have: if (indexPath.row == cellCount) { ... stuff goes here return cell; } of course, this never gets called. If I do if (indexPath.row == cellCount -1) it overwrites the last cell with content. I can get this to work if I add a blank entry into the xml from which I am populating the dictionary, but that's ugly. Example code would be neat!

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  • Select data from three different tables with null data

    - by user3678972
    I am new in Sql. My question is how to get data from three different tables with null values. I have tried a query as below: SELECT * FROM [USER] JOIN [Location] ON ([Location].UserId = [USER].Id) JOIN [ParentChild] ON ([ParentChild].UserId = [USER].Id) WHERE ParentId=7 which I find from this link. Its working fine but, it not fetches all and each data associated with the ParentId Something like it only fetches data which are available in all tables, but also omits some data which not available in Location tables but it comes under the given ParentId. For example: UserId ParentId 1 7 8 7 For userId 8, there is data available in Location table,so it fetches all data. But there is no data for userId 1 available in Location table, so the query didn't work for this. But I want all and every data. If there is no data for userId then it can return only null columns. Is it possible ?? hope everyone can understand my problem.

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  • mysql: select ... where id = any value. is it possible?

    - by Syom
    look at this table please table |id| |name| |order| i must get the rows, where name = something and order = somevalue so i write select `id` from `table` where `name` = 'something' and `order` = 'somevalue' but depend on php logic, sometimes i need to get all rows, where name = somethimg, independently of order value. i don't want to change the query structure, because in practise there are many number of fields, and possible count of queries will became very big. so i want to save the structure of query, and when i need to select just by name, i want to write something like this select `id` from `table` where `name` = 'something' and `order` = any value is it possible? maybe the question is incomprehensible, at least i tried;) sorry for bad english thanks

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  • Implement subitem in SQLite

    - by Mohit Deshpande
    How could I implement a sub item where the item would have a parent to that of the same item. For example, I have a database that holds tasks/todos. Each todo has a title(TEXT), completed(INTEGER [1 if true, 0 if false]), and due date(TEXT) column. I would like to add functionality to have subtasks, where a task could possibly have a parent task. How would I implement this in SQLite for Android? NOT IN SQL! So no foreign keys (triggers are allow, though)! Could I just have a separate table (subtask) and have a foreign key trigger to link subtask(INTEGER parent) to task(INTEGER PRIMARY KEY AUTOINCREMENT _id)? Or should I add a column to my original task table(INTEGER parent)? How could I implement this?

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  • [Django] How to find out whether a model's column is a foreign key?

    - by codethief
    I'm dynamically storing information in the database depending on the request: // table, id and column are provided by the request table_obj = getattr(models, table) record = table_obj.objects.get(pk=id) setattr(record, column, request.POST['value']) The problem is that request.POST['value'] sometimes contains a foreign record's primary key (i.e. an integer) whereas Django expects the column's value to be an object of type ForeignModel: Cannot assign "u'122'": "ModelA.b" must be a "ModelB" instance. Now, is there an elegant way to dynamically check whether b is a column containing foreign keys and what model these keys are linked to? (So that I can load the foreign record by it's primary key and assign it to ModelA?) Or doesn't Django provide information like this to the programmer so I really have to get my hands dirty and use isinstance() on the foreign-key column?

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  • What is the best way to add categories to posts - Ruby on Rails blog...

    - by bgadoci
    I am new to Ruby and Rails so bear with me please. I have created a very simple blog application with both posts and comments. Everything works great. My next question regarding adding categories. I am wondering the best way to do this. As I can't see too far in front of me yet when it comes to Rails I thought I would ask. To be clear, I would like that a single post can have multiple categories and a category can have multiple posts. Is the best way to do this to create a 'categories' table and then use the posts and categories models to do has_many :posts, has_many :categories? Would I also then set the routes.rb such that posts are embedded under categories? Or is there an easier way by simply adding a category column to the existing posts table? (in which case I would imagine having multiple categories would be difficult).

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  • Nhibernate: mapping two different properties between the same 2 entities

    - by Carlos Decas
    I have a Class A: public class ClassA { public int ID {get; private set;} public string Code {get; private set;} public ClassB B {get; private set;} public IList<ClassB> ListB {get; private set;} } And a ClassB: public class ClassB { public int ID {get; private set;} public string Code {get; private set;} public ClassA A {get; private set;} //some other attributes... } And the Mappings: public ClassAMap() { Table("ClassA"); Id(classA => classA .ID, "ID").GeneratedBy.Identity(); Map(classA => classA.Code, "Code").Unique().Not.Nullable(); //HERE IS THE PROBLEM: -------- References(classA => classA.B,"IDClassB").Cascade.SaveUpdate(); //----- HasMany(classA => classA.ListB).Table("ClassB").KeyColumn("IDClassA").AsBag().Not.LazyLoad().Inverse().Cascade.AllDeleteOrphan(); } ClassB Mappings: public ClassBMap() { Table("ClassB"); Id(classB => classB.ID).GeneratedBy.Identity(); References(classB => classB.A, "IDClassA").ForeignKey("ID").Cascade.SaveUpdate(); } The mappings for ListB in classA worked ok, because at first the was only ListB property and not B, when i had to map B i tried this: References(classA => classA.B,"IDClassB"); The mapping test failed because B wasn't saved, so i did this: References(classA => classA.B,"IDClassB").Cascade.SaveUpdate(); This time B was saved, but by saving B, classA was inserted two times, by A.B and by B.A. How can i solve this problem? Why does it work for the ListB property and not for the B property? Thanks

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  • How to programmatically set a data cell of database in VB.Net?

    - by manuel
    I have a Microsoft Access database file connected to VB.NET. In the database table, I have a 'No.' and a 'Status' column. Then I have a textbox where I can input an integer. I also have a button, which will change the data cell in 'Status' where 'No.' = textbox.Text(), when I click it. Let's say I want the 'Status' cell to be changed to "Low". What codes should I put in the button_Click event handler? Here is the codes I used to retrieve and display the database table. Public Class theForm Dim con As New OleDb.OleDbConnection Dim ds As New DataSet Dim daTitles As OleDb.OleDbDataAdapter Private Sub theForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load con.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=|DataDirectory|\db1.mdb" con.Open() daTitles = New OleDb.OleDbDataAdapter("SELECT * FROM Titles", con) daTitles.Fill(ds, "Titles") DataGridView1.DataSource = ds.Tables("Titles") DataGridView1.AutoResizeColumns() End Sub

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  • Difference in linq-to-sql query performance using GenericRespositry

    - by Neil
    Given i have a class like so in my Data Layer public class GenericRepository<TEntity> where TEntity : class { [System.ComponentModel.DataObjectMethod(System.ComponentModel.DataObjectMethodType.Select)] public IQueryable<TEntity> SelectAll() { return DataContext.GetTable<TEntity>(); } } I would be able to query a table in my database like so from a higher layer using (GenericRepositry<MyTable> mytable = new GenericRepositry<MyTable>()) { var myresult = from m in mytable.SelectAll() where m.IsActive select m; } is this considerably slower than using the usual code in my Data Layer using (MyDataContext ctx = new MyDataContext()) { var myresult = from m in ctx.MyTable where m.IsActive select m; } Eliminating the need to write simple single table selects in the Data layer saves a lot of time, but will i regret it?

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  • How do I add a one-to-one relationship in MYSQL?

    - by alex
    +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | pid | varchar(99) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 1 row in set (0.00 sec) +-------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------+------+-----+---------+-------+ | pid | varchar(2000) | YES | | NULL | | | recid | varchar(2000) | YES | | NULL | | +-------+---------------+------+-----+---------+-------+ 2 rows in set (0.00 sec) This is my table. pid is just the id of the user. "recid" is a recommended song for that user. I hope to have a list of pid's, and then recommended songs for each person. Of course, in my 2nd table, (pid, recid) would be unique key. How do I do a one-to-one query for this ?

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  • In SQL, we can use "Union" to merge two tables. What are different ways to do "Intersection"?

    - by Jian Lin
    In SQL, there is an operator to "Union" two tables. In an interview, I was told that, say one table has just 1 field with 1, 2, 7, 8 in it, and another table also has just 1 field with 2, and 7 in it, how do I get the intersection. I was stunned at first, because I never saw it that way. Later on, I found that it is actually a "Join" (inner join), which is just select * from t1, t2 where t1.number = t2.number (although the name "join" feels more like "union" rather than "intersect") another solution seems to be select * from t1 INTERSECT select * from t2 but it is not supported in MySQL. Are there different ways to get the intersection besides these two methods?

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  • many to many query for ActiveRecord

    - by JP
    I have three data models, Users, Conversations and Lines, where each conversation has many lines and certain participating users, each line has one conversation and one user and each user has many conversations and many lines. I have arranged these in ActiveRecord like this: class Line < ActiveRecord::Base belongs_to :conversation belongs_to :user end class User < ActiveRecord::Base has_and_belongs_to_many :conversations has_many :lines end class Conversation < ActiveRecord::Base has_many :lines has_and_belongs_to_many :users end If I want to create a new conversation with 4 users, where the users are either found or created inside the users table, how would I go about doing this? I thought I could do: c = Conversation.new c.users.find_or_create_by_username('myUsername') c.save But this will create a new username in the Users table even if that username already exists! (ie. running the above code 3 times will result in Users having 3 rows with 'myUsername' as the username, one for each conversation, rather than three conversations all with the same 'myUsername' entry listed in their associated users) I'm not sure how to search for this kind of information with google - can anyone help?

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  • How to persist non-trivial fields in Play Framework

    - by AlexR
    I am trying to persist complex objects using Ebeans in Play Framework (2.03). In particular, I've created a class that contains a field of type weka.classifier.Classifier (Weka is a popular machine learning library - see http://weka.sourceforge.net/doc/weka/classifiers/Classifier.html). Classifier implements Serializeable so I hoped that I can get away with something like @Entity @Table(name = "classifiers") public class ClassifierData extends Model { @Id public Long id; public Classifier classifier; } However, the Evolutions script suggests the following database structure: create table classifiers ( id bigint auto_increment not null, constraint pk_classifiers primary key (id)) ) In other words, it ignores the field of type Classifier. (The database is MySQL if it makes any difference) What should I do to store complex serializeable objects using Ebean/Evolutions/PlayFramework?

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  • The use of GROUP BY in MySQL

    - by Gustav Bertram
    I'm fishing for a comprehensive and canonical answer for the typical "mysql group by?" question. Here is some sample data: TABLE A +------+------+----------+-----+ | id | foo | bar | baz | +------+------+----------+-----+ | 1 | 1 | hello | 42 | | 2 | 0 | apple | 96 | | 3 | 20 | boot | 11 | | 4 | 31 | unicorn | 99 | | 5 | 19 | pumpkin | 11 | | 6 | 88 | orange | 13 | +------+------+----------+-----+ TABLE B +------+------+ | id | moo | +------+------+ | 1 | 1 | | 2 | 99 | | 3 | 11 | +------+------+ Demonstrate and explain the correct use of the GROUP BY clause in MySQL. Touch upon the following points: The use of MIN, MAX, SUM, AVG The use of HAVING Grouping by date, and ranges of dates Grouping with an ORDER BY Grouping with a JOIN Grouping on multiple columns Bonus points for references to other great answers, the MySQL online manual, and online tutorials on GROUP BY.

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