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• Can I clone an IQueryable in linq? For UNION purposes?

  - by user169867

  I have a table of WorkOrders. The table has a PrimaryWorker & PrimaryPay field. It also has a SecondaryWorker & SecondaryPay field (which can be null). I wish to run 2 very similar queries & union them so that it will return a Worker Field & Pay field. So if a single WorkOrder record had both the PrimaryWorker and SecondaryWorker field populated I would get 2 records back. The "where clause" part of these 2 queries is very similar and long to construct. Here's a dummy example var q = ctx.WorkOrder.Where(w => w.WorkDate >= StartDt && w.WorkDate <= EndDt); if(showApprovedOnly) { q = q.Where(w => w.IsApproved); } //...more filters applied Now I also have a search flag called "hideZeroPay". If that's true I don't want to include the record if the worker was payed $0. But obviously for 1 query I need to compare the PrimaryPay field and in the other I need to compare the SecondaryPay field. So I'm wondering how to do this. Can I clone my base query "q" and make a primary & secondary worker query out of it and then union those 2 queries together? I'd greatly appreciate an example of how to correctly handle this. Thanks very much for any help.

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• delete vs execSQL commands android

  - by erik

  so i have a databas, SQLiteDatabase db I am writing a couple private methods in my manager class that will be called by a public method: public void updateData (MakeabilityModel newData){ SQLiteDatabase db = this.getWritableDatabase(); db.beginTransaction(); try { reWriteSVTable(db, list); db.setTransactionSuccessful(); } catch (Exception e){ //TODO through rollback message? e.printStackTrace(); } finally { db.endTransaction(); } } //Private Methods private void clearTable(SQLiteDatabase db, String table){ db.delete(table, null, null); } private void reWriteSVTable(SQLiteDatabase db, List<MakeabilityLens> lenses){ clearTable(db, singleVision); ContentValues cv; for(int i=0; i<lenses.size(); i++){ cv = new ContentValues(); cv.put(colScreenID, hsID); cv.put(colIconID, id); cv.put(colRank, hsTotal); db.insert(isLookUp, colID, cv); } } My question is this.. i want to be able to throw sql exceptions back to the public method so that if there is an exception, it will kill the transaction and rollback ALL data.. it appears that using delete() and insert() methods are cleaner than execSQL() but don't throw sqlExceptions. execSQL() on the other hand does? do i need to uses execSQL and how do i insure that hsould it throws an exception in any of the private methods that it will catch it and roll it back in the private method

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• Editable, growable DataGrid that retains values on postback and updates underlying DataTable

  - by jlstrecker

  I'm trying to create an ASP.NET/C# page that allows the user to edit a table of data, add rows to it, and save the data back to the database. For the table of data, I'm using a DataGrid whose cells contain TextBoxes or CheckBoxes. I have a button for adding rows (which works) and a button for saving the data. However, I'm quite stuck on two things: The TextBoxes and CheckBoxes should retain their values on postback. So if the user edits a TextBox and clicks the button to add more rows, the edits should be retained when the page reloads. However, the edits should not be saved to the database at this point. When the user clicks the save button, or anytime before, the DataTable underlying the DataGrid needs to be updated with the values of the TextBoxes and CheckBoxes so that the DataTable can be sent to the database. I have a method that does this, but I can't figure out when to call it. Any help getting this to work, or suggestions of alternative user interfaces that would behave similarly, would be appreciated.

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• mysql row locking via php

  - by deezee

  I am helping a friend with a web based form that is for their business. I am trying to get it ready to handle multiple users. I have set it up so that just before the record is displayed for editing I am locking the record with the following code. $query = "START TRANSACTION;"; mysql_query($query); $query = "SELECT field FROM table WHERE ID = \"$value\" FOR UPDATE;"; mysql_query($query); (okay that is greatly simplified but that is the essence of the mysql) It does not appear to be working. However, when I go directly to mysql from the command line, logging in with the same user and execute START TRANSACTION; SELECT field FROM table WHERE ID = "40" FOR UPDATE; I can effectively block the web form from accessing record "40" and get the timeout warning. I have tried using BEGIN instead of START TRANSACTION. I have tried doing SET AUTOCOMMIT=0 first and starting the transaction after locking but I cannot seem to lock the row from the PHP code. Since I can lock the row from the command line I do not think there is a problem with how the database is set up. I am really hoping that there is some simple something that I have missed in my reading. FYI, I am developing on XAMPP version 1.7.3 which has Apache 2.2.14, MySQL 5.1.41 and PHP 5.3.1. Thanks in advance. This is my first time posting but I have gleaned alot of knowledge from this site in the past.

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• Web Shop Schema - Document Db

  - by Maxem

  I'd like to evaluate a document db, probably mongo db in an ASP.Net MVC web shop. A little reasoning at the beginning: There are about 2 million products. The product model would be pretty bad for rdbms as there'd be many different kinds of products with unique attributes. For example, there'd be books which have isbn, authors, title, pages etc as well as dvds with play time, directors, artists etc and quite a few more types. In the end, I'd have about 9 different products with a combined column count (counting common columns like title only once) of about 70 to 100 whereas each individual product has 15 columns at most. The three commonly used ways in RDBMS would be: EAV model which would have pretty bad performance characteristics and would make it either impractical or perform even worse if I'd like to display the author of a book in a list of different products (think start page, recommended products etc.). Ignore the column count and put it all in the product table: Although I deal with somewhat bigger databases (row wise), I don't have any experience with tables with more than 20 columns as far as performance is concered but I guess 100 columns would have some implications. Create a table for each product type: I personally don't like this approach as it complicates everything else. C# Driver / Classes: I'd like to use the NoRM driver and so far I think i'll try to create a product dto that contains all properties (grouped within detail classes like book details, except for those properties that should be displayed on list views etc.). In the app I'll use BookBehavior / DvdBehaviour which are wrappers around a product dto but only expose the revelent Properties. My questions now: Are my performance concerns with the many columns approach valid? Did I overlook something and there is a much better way to do it in an RDBMS? Is MongoDb on Windows stable enough? Does my approach with different behaviour wrappers make sense?

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• how to get Contact database schema.

  - by kamiomar

  Dear, is there any link that provide me the Contact Schema. when i store new phone number in mobile, the informaion store in the database. so i need schema to create my own table for back purpose. i have alreay get People table column by the follwoing code. boolean displayFlag = false; String str = ""; Uri CONTACT_URI = People.CONTENT_URI; Cursor cursor = mContext.getContentResolver().query(CONTACT_URI, null, null, null, null); String columnNames = ""; if (cursor != null) { try { cursor.getCount(); if (cursor.moveToFirst()) { String[] columns = cursor.getColumnNames(); for (int i = 0; i < columns.length; i++) { columnNames += "colName" + cursor.getColumnName(i) + " : " + cursor.getString(i) + "colValue"; } } } finally { cursor.close(); } } createImage(columnNames); if (displayFlag) { Toast.makeText(mContext, str, Toast.LENGTH_SHORT).show(); } } Thanks

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• Most efficient way to make an activity log

  - by Nathan

  I am making a "recent activity" tab to profiles on my site and I also am going to have a log for moderators to see everything that happens on the site. This would require making an activity log of some sort. I just don't know what would be better. I have 2 options: Make a table called "activity" and then every time someone does something, add a record to it with the type of action, user id, timestamp, etc. Problem: table could get very long. Join all 3 tables (questions, answers, answer_comments) and then somehow show all these on the page in the order in which the action was taken. Problem: this would be extremely hard because I have no clue how I could make it say "John commented on an answer on Question Title Here" by just joining 3 tables. Does anyone know of a better way of making an activity log in this situation? I am using PHP and MySQL. If this is either too inefficient or hard I will probably just forget the Recent Activity tab on profiles but I still need an activity log for moderators. Here's some SQL that I started making for option 2, but this would not work because there is no way of detecting whether the action is a comment, question, or answer when I echo the info in a while loop: SELECT q.*, a.*, ac.* FROM questions q JOIN answers a ON a.questionid = q.qid JOIN answer_comments ac ON c.answerid = a.ans_id WHERE q.user = $userid AND a.userid = $userid AND ac.userid = $userid ORDER BY q.created DESC, a.created DESC, ac.created DESC Thanks in advance for any help!

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• How to access view items inside a ListView android?

  - by Yasir Khan

  I have ListView. i am successfully able to populate that ListView but what is want now is when user long press on ListItem it should make a button visible which i made invisible when i am populating ListView. here is snippet i have tried. mItemListView.setOnItemLongClickListener(new OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView<?> adapterview, View arg1, int arg2, long arg3) { LinearLayout view=(LinearLayout) mItemListView.getChildAt(arg2); view.getChildAt(0).setVisibility(View.VISIBLE); return false; } }); My adapter is extending BaseAdapter

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• World's Most Challening MySQL SQL Query (least I think so...)

  - by keruilin

  Whoever answers this question can claim credit for solving the world's most challenging SQL query, according to yours truly. Working with 3 tables: users, badges, awards. Relationships: user has many awards; award belongs to user; badge has many awards; award belongs to badge. So badge_id and user_id are foreign keys in the awards table. The business logic at work here is that every time a user wins a badge, he/she receives it as an award. A user can be awarded the same badge multiple times. Each badge is assigned a designated point value (point_value is a field in the badges table). For example, BadgeA can be worth 500 Points, BadgeB 1000 Points, and so on. As further example, let's say UserX won BadgeA 10 times and BadgeB 5 times. BadgeA being worth 500 Points, and BadgeB being worth 1000 Points, UserX has accumulated a total of 10,000 Points ((10 x 500) + (5 x 1000)). The end game here is to return a list of top 50 users who have accumulated the most badge points. Can you do it?

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• Using jQuery with Windows 8 Metro JavaScript App causes security error

  - by patridge

  Since it sounded like jQuery was an option for Metro JavaScript apps, I was starting to look forward to Windows 8 dev. I installed Visual Studio 2012 Express RC and started a new project (both empty and grid templates have the same problem). I made a local copy of jQuery 1.7.2 and added it as a script reference. <!-- SomeTestApp references --> <link href="/css/default.css" rel="stylesheet" /> <script src="/js/jquery-1.7.2.js"></script> <script src="/js/default.js"></script> Unfortunately, as soon as I ran the resulting app it tosses out a console error: HTML1701: Unable to add dynamic content ' a' A script attempted to inject dynamic content, or elements previously modified dynamically, that might be unsafe. For example, using the innerHTML property to add script or malformed HTML will generate this exception. Use the toStaticHTML method to filter dynamic content, or explicitly create elements and attributes with a method such as createElement. For more information, see http://go.microsoft.com/fwlink/?LinkID=247104. I slapped a breakpoint in a non-minified version of jQuery and found the offending line: div.innerHTML = " <link/><table></table><a href='/a' style='top:1px;float:left;opacity:.55;'>a</a><input type='checkbox'/>"; Apparently, the security model for Metro apps forbids creating elements this way. This error doesn't cause any immediate issues for the user, but given its location, I am worried it will cause capability-discovery tests in jQuery to fail that shouldn't. I definitely want jQuery $.Deferred for making just about everything easier. I would prefer to be able to use the selector engine and event handling systems, but I would live without them if I had to. How does one get the latest jQuery to play nicely with Metro development?

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• SQL Server 2008 spatial index and CPU utilization with MapGuide Open Source 2.1

  - by Antonio de la Peña

  I have a SQL Server table with hundreds of thousands of geometry type parcels. I have made indexes on them trying different combinations of density and objects per cell settings. So far I'm settiling for LOW, LOW, MEDIUM, MEDIUM and 16 objects per cell and I made a SP that sets the bounding box according to the extents of the entities in the table. There is an incredible performance boost from queries taking almost minutes without index to less than seconds, it gets faster when the zoom is closer thus less objects are displayed. Yet the CPU utilization gets to 100% when querying for features, even when the queries themselves are fast. I'm worrying this will not fly in a production environment. I am using MapGuide Open Source 2.1 for this project, but I am positive the CPU load is caused by SQL Server. I wonder if my indexes are set properly. I haven't found any clear documentation on how to properly set them up. Every article I've read basically says "it depends..." but nothing specific. Do you have any recommendations for me, including books, articles? Thank you.

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• abstract class MouseAdapter vs. interface

  - by Stefano Borini

  I noted this (it's a java.awt.event class). public abstract class MouseAdapter implements MouseListener, MouseWheelListener, MouseMotionListener { .... } Then you are clearly forced to extend from this adapter public class MouseAdapterImpl extends MouseAdapter {} the class is abstract and implements no methods. Is this a strategy to combine different interfaces into a single "basically interface" ? I assume in java it's not possible to combine different interfaces into a single one without using this approach. In other words, it's not possible to do something like this in java public interface MouseAdapterIface extends MouseListener, MouseWheelListener, MouseMotionListener { } and then eventually public class MouseAdapterImpl implements MouseAdapterIface {} Is my understanding of the point correct ? what about C# ?

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• How to Specify Columntype in fluent nHibernate?

  - by Bipul

  I have a class CaptionItem public class CaptionItem { public virtual int SystemId { get; set; } public virtual int Version { get; set; } protected internal virtual IDictionary<string, string> CaptionValues {get; private set;} } I am using following code for nHibernate mapping Id(x => x.SystemId); Version(x => x.Version); Cache.ReadWrite().IncludeAll(); HasMany(x => x.CaptionValues) .KeyColumn("CaptionItem_Id") .AsMap<string>(idx => idx.Column("CaptionSet_Name"), elem => elem.Column("Text")) .Not.LazyLoad() .Cascade.Delete() .Table("CaptionValue") .Cache.ReadWrite().IncludeAll(); So in database two tables get created. One CaptionValue and other CaptionItem. In CaptionItem table has three columns 1. CaptionItem_Id int 2. Text nvarchar(255) 3. CaptionSet_Name nvarchar(255) Now, my question is how can I make the columnt type of Text to nvarchar(max)? Thanks in advance.

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• Writing csv file in asp.net

  - by Keith

  Hello, I'm trying to export data to a csv file, as there are chinese characters in the data i had to use unicode.. but after adding the preamble for unicode, the commas are not recognized as delimiters and all data are now written to the first column. I'm not sure what is wrong. Below is my code which i wrote in a .ashx file. DataView priceQuery = (DataView)context.Session["priceQuery"]; String fundName = priceQuery.Table.Rows[0][0].ToString().Trim().Replace(' ', '_'); context.Response.Clear(); context.Response.ClearContent(); context.Response.ClearHeaders(); context.Response.ContentType = "text/csv"; context.Response.ContentEncoding = System.Text.Encoding.Unicode; context.Response.AddHeader("Content-Disposition", "attachment; filename=" + fundName + ".csv"); context.Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble()); String output = fundName + "\n"; output += "Price, Date" + "\n"; foreach (DataRow row in priceQuery.Table.Rows) { string price = row[2].ToString(); string date = ((DateTime)row[1]).ToString("dd-MMM-yy"); output += price + "," + date + "\n"; } context.Response.Write(output);

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• How to pass data from selected rows using checkboxes from JSP to the server

  - by eddy

  Hi, I'd like to know if there's any way to send data to the server for the selected rows using the checkboxes I've put on those rows? I mean , how can I send only the data (in this case mileage ) of those selected rows (selected with the checkboxes) to the server ? see the image Here's the html code I use: <table> <thead> <tr class="tableheader"> <td width="10%"></td> <td width="30%">Vehicle</td> <td width="40%">Driver</td> <td width="10%">Mileage</td> </tr> </thead> <tbody> <c:forEach items="${list}" var="item"> <tr> <td align="center"> <input type="checkbox" name="selectedItems" value="c:out value="${item.numberPlate}"/>"/> </td> <td align="left"><c:out value="${item.numberPlate}"/></td> <td align="left"><c:out value="${item.driver.fullName}" /></td> <td align="left"><input type="text" name="mileage" value="" /></td> </tr> </c:forEach> </tbody> </table> I really hope you can give some guidance on this. Thanks in beforehand.

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• Hibernate not saving foreign key, but with junit it's ok

  - by Leonardo

  Hi All, I have this strange problem. In a J2ee webapp with spring, smartgwt and hibernate, it happens that I have a class A wich has a set of class B, both of them mapped to table A and table B. I wrote a simple test case for testing the service manager which is supposed to do insert, update, delete and everything work as expected especially during insert. In the end I have one record in A and records in B with foreign key to A. But when I try to call the service from the web app, the entity in B are saved without a foreign key reference. I am sure that the service is the same. One thing I noticed is that enabling hibernate logging, seems that when the service is called from the application, one more update is made: insert A insert B update A update B update B (foreign key only) update A <--- ??? update B <--- ??? Instead, when junit test case is run, the update is as follows: insert A insert B update A update B update B (foreign key only) I suppose the latest update is what is causing the erroe, maybe it is overwriting values. Considering that the app is using spring, with the well known mechanism of DAO + Manager, where can I investigate to solve this issue ? Someone told me that the session is not closed, so hibernate would do one more update before release the objects by itself. I am pretty sure that all the configuration hbm, xml, and the rest are fine...but I maybe wrong. thanks

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• display tag query

  - by sarah

  I have code: <display:table name="sessionScope.allUserslist" id="userList" export="false" pagesize="1"> <display:column title="Select" style="width: 90px;"> <input type="checkbox" name="optionSelected" value="<c:out value='${userList.loginName}'/>"/> </display:column> <display:column property="loginName" sortable="false" title="UserName" paramId="loginName" style="width: 150px; text-align:center" href="./editUser.do?method=editUser"/> <display:column property="role" sortable="false" title="UserRole" paramId="role" style="width: 150px; text-align:center"/> </display:table> On click of login name, I am moving to a new page where I need to get all the of user, I am just getting the name not the role, on click of link I am calling an action where in the method I am trying to read the data from the form using User u=(User)form; u.getRole(); but it's null. Where am I going wrong ?

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• Hibernate saveorUpdate method problem

  - by umesh awasthi

  Hi all, i am trying to work on with Hibernate (Database side for first time) and some how struck in choosing best possible way to use saveOrUpdate or Save.Update i have a destination POJO class and its other attributes which needs to be updated along with the Destination entity. i am getting an XML file to be imported and i am using the following code to update/save the destination entity along with its attribute classes. try{ getSessionFactory().getCurrentSession().beginTransaction(); getSessionFactory().getCurrentSession().saveOrUpdate(entity); getSessionFactory().getCurrentSession().getTransaction().commit(); } catch(Exception e){ getSessionFactory().getCurrentSession().getTransaction().rollback(); } finally{ getSessionFactory().close(); } everything is working fine untill i am using the same session instance.but later on when i am using the same XML file to update the destination PO for certain attributes it giving me the following error. SEVERE: Duplicate entry 'MNLI' for key 'DESTINATIONID' 9 Jan, 2011 4:58:11 PM org.hibernate.event.def.AbstractFlushingEventListener performExecutions SEVERE: Could not synchronize database state with session org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:94) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:275) at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:114) at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:109) at org.hibernate.jdbc.AbstractBatcher.prepareBatchStatement(AbstractBatcher.java:244) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2242) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2678) at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:79) i am using UUID as primary key for the Destination table and in destination table i have a destination id which is unique.but i can understand that in the secodn case hibernate is not able to find if there is already an entry for the same destination in the DB and trying to execute insert statement rather than update. one possible solution is i can user destinationid to check if there is already a destination inplace with the given id and based on the results i can issue save or update command. my question is can this be achieve by any other good way..? Thanks in advance

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• NHibernate listener/event to replace object before insert/update

  - by vIceBerg

  Hi! I have a Company class which have a collection of Address. Here's my Address class:(written top of my head): public class Address { public string Civic; public string Street; public City City; } This is the City class: public class City { public int Id; public string Name; public string SearchableName{ get { //code } } } Address is persisted in his own table and have a reference to the city's ID. City are also persisted in is own table. The City's SearchableName is used to prevent some mistakes in the city the user type. For example, if the city name is "Montréal", the searchable name will be "montreal". If the city name is "St. John", the searchable name will be "stjohn", etc. It's used mainly to to search and to prevent having multiple cities with a typo in it. When I save an address, I want an listener/event to check if the city is already in the database. If so, cancel the insert and replace the user's city with the database one. I would like the same behavior with updates. I tried this: public bool OnPreInsert(PreInsertEvent @event) { City entity = (@event.Entity as City); if (entity != null) { if (entity.Id == 0) { var city = (from c in @event.Session.Linq<City>() where c.SearchableName == entity.SearchableName select c).SingleOrDefault(); if (city != null) { //don't know what to do here return true; } } } return false; } But if there's already a City in the database, I don't know what to do. @event.Entity is readonly, if I set @event.Entity.Id, I get an "null identifier" exception. I tried to trap insert/update on Address and on Company, but the City if the first one to get inserted (it's logic...) Any thoughts? Thanks

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• Need help with a SQL CTE Query

  - by Chuck

  I have a table that I need to get some specific data from for a view. Here's the base table structure with some sample data: | UserID | ReportsToUserID | Org ID | ------------------------------------- | 1 | NULL | 1 | ------------------------------------- | 2 | 1 | 1 | ------------------------------------- | 3 | 2 | 1 | ------------------------------------- | 4 | 3 | 1 | ------------------------------------- The users will be entering reports and users can see the reports of users who report to them and any users who report to those users. Users who report to no one can see everything in their organization Given my sample data above, user 1 can see the reports of 2, 3, & 4; user 2 can see the reports of 3 & 4; and user 3 can see the reports of 4. For the view, I'd like to have the data returned as follows: | UserID | CanSeeUserID | OrgID | -------------------------------------------- | 1 | 2 | 1 | -------------------------------------------- | 1 | 3 | 1 | -------------------------------------------- | 1 | 4 | 1 | -------------------------------------------- | 2 | 3 | 1 | -------------------------------------------- etc... Below is my current code, any help is greatly appreciated. WITH CTEUsers (UserID, CanSeeUserID, OrgID) AS ( SELECT e.ID, e.ReportsToUserID, e.OrgID FROM Users e WITH(NOLOCK) WHERE COALESCE(ReportsToUserID,0) = 0 --ReportsToUserID can be NULL or 0 UNION ALL SELECT e.ReportsToUserID, e.ID,e.OrgID FROM Users e WITH(NOLOCK) JOIN CTEUsers c ON e.ID = c.UserID ) SELECT * FROM CTEUsers

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• How can I get the rank of rows relative to total number of rows based on a field?

  - by Arms

  I have a scores table that has two fields: user_id score I'm fetching specific rows that match a list of user_id's. How can I determine a rank for each row relative to the total number of rows, based on score? The rows in the result set are not necessarily sequential (the scores will vary widely from one row to the next). I'm not sure if this matters, but user_id is a unique field. Edit @Greelmo I'm already ordering the rows. If I fetch 15 rows, I don't want the rank to be 1-15. I need it to be the position of that row compared against the entire table by the score property. So if I have 200 rows, one row's rank may be 3 and another may be 179 (these are arbitrary #'s for example only). Edit 2 I'm having some luck with this query, but I actually want to avoid ties SELECT s.score , s.created_at , u.name , u.location , u.icon_id , u.photo , (SELECT COUNT(*) + 1 FROM scores WHERE score > s.score) AS rank FROM scores s LEFT JOIN users u ON u.uID = s.user_id ORDER BY s.score DESC , s.created_at DESC LIMIT 15 If two or more rows have the same score, I want the latest one (or earliest - I don't care) to be ranked higher. I tried modifying the subquery with AND id > s.id but that ended up giving me an unexpected result set and different ties.

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• How to model has_many with polymorphism?

  - by Daniel Abrahamsson

  I've run into a situation that I am not quite sure how to model. Suppose I have a User class, and a user has many services. However, these services are quite different, for example a MailService and a BackupService, so single table inheritance won't do. Instead, I am thinking of using polymorphic associations together with an abstract base class: class User < ActiveRecord::Base has_many :services end class Service < ActiveRecord::Base validates_presence_of :user_id, :implementation_id, :implementation_type belongs_to :user belongs_to :implementation, :polymorphic = true delegate :common_service_method, :name, :to => :implementation end #Base class for service implementations class ServiceImplementation < ActiveRecord::Base validates_presence_of :user_id, :on => :create has_one :service, :as => :implementation has_one :user, :through => :service after_create :create_service_record #Tell Rails this class does not use a table. def self.abstract_class? true end #Default name implementation. def name self.class.name end protected #Sets up a service object def create_service_record service = Service.new(:user_id => user_id) service.implementation = self service.save! end end class MailService < ServiceImplementation #validations, etc... def common_service_method puts "MailService implementation of common service method" end end #Example usage MailService.create(..., :user_id => user.id) BackupService.create(...., :user_id => user.id) user.services.each do |s| puts "#{user.name} is using #{s.name}" end #Daniel is using MailService, Daniel is using BackupService So, is this the best solution? Or even a good one? How have you solved this kind of problem?

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• Ruby on Rails Associations

  - by Eef

  Hey all, I am starting to create my sites in Ruby on Rails these days instead of PHP. I have picked up the language easily but still not 100% confident with associations :) I have this situation: User Model has_and_belongs_to_many :roles Roles Model has_and_belongs_to_many :users Journal Model has_and_belongs_to_many :roles So I have a roles_users table and a journals_roles table I can access the user roles like so: user = User.find(1) User.roles This gives me the roles assigned to the user, I can then access the journal model like so: journals = user.roles.first.journals This gets me the journals associated with the user based on the roles. I want to be able to access the journals like so user.journals In my user model I have tried this: def journals self.roles.collect { |role| role.journals }.flatten end This gets me the journals in a flatten array but unfortunately I am unable to access anything associated with journals in this case, e.g in the journals model it has: has_many :items When I try to access user.journals.items it does not work as it is a flatten array which I am trying to access the has_many association. Is it possible to get the user.journals another way other than the way I have shown above with the collect method? Hope you guys understand what I mean, if not let me know and ill try to explain it better. Cheers Eef

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• Update or Insert Row depending on whether row is present in Microsoft SQL Server 2005

  - by Srikanth

  Hi, I am passing a XML document as a input to a stored procedure in Microsoft SQL Server 2005. This is the sample XML being passed as input <Strategy StrategyID="0" TOStrategyID="8" ShutdownQtySell="1" ShutdownQtyBuy="1"> <ParameterRange ParameterSetID="6" ParameterRangeID="1" ParameterRangeFrom="0" ParameterRangeTo="20" ParameterAutoTakeOut="False"> </ParameterRange> <ParameterRange ParameterSetID="6" ParameterRangeID="4" ParameterRangeFrom="21" ParameterRangeTo="40" ParameterAutoTakeOut="False"> </ParameterRange> <ParameterRange ParameterSetID="6" ParameterRangeID="5" ParameterRangeFrom="41" ParameterRangeTo="60" ParameterAutoTakeOut="False"> </ParameterRange> <ParameterRange ParameterSetID="6" ParameterRangeID="6" ParameterRangeFrom="61" ParameterRangeTo="80" ParameterAutoTakeOut="False"> </ParameterRange> <ParameterRange ParameterSetID="6" ParameterRangeID="7" ParameterRangeFrom="81" ParameterRangeTo="100" ParameterAutoTakeOut="False"> </ParameterRange> </Strategy> I am able to retrieve the data using OpenXML functionality in SQL server I am using this to get the data corresponding to ParameterRange rows SELECT ParameterRangeID as iRangeID, ParameterSetID as iSetID, ParameterRangeFrom as fRangeFrom, ParameterRangeTo as fRangeTo, ParameterAutoTakeOut as bTakeoutEnabled FROM OPENXML(@idoc, '/Strategy/ParameterRange', 1) WITH (ParameterSetID int,ParameterRangeID int,ParameterRangeFrom float,ParameterRangeTo float,ParameterAutoTakeOut bit) Now, I need to insert/update these rows into a table TempRanges which has (iRangeID,iSetID) as the primary key. If there is a row with the primary key, I want to update it the latest values and If there is no row with that primary key, I need to insert into the table. How can I accomplish this inside the Stored Procedure ? Thanks, Sri

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• MYSQL JOIN WHERE ISSUES - need some kind of if condition

  - by Breezer

  Hi Well this will be hard to explain but ill do my best The thing is i have 4 tables all with a specific column to relate to eachother. 1 table with users(agent_users) , 1 with working hours(agent_pers), 1 with sold items(agent_stat),1 with project(agent_pro) the user and the project table is irrelevant in the issue at hand but to give you a better understanding why certain tables is included in my query i decided to still mention them =) The thing is that I use 2 pages to insert data to the working hour and the sold items during that time tables, then i have a third page to summarize everything for current month, the query for that is as following: SELECT *, SUM(sv_p_kom),SUM(sv_p_gick),SUM(sv_p_lunch) FROM (( agent_users LEFT JOIN agent_pers ON agent_users.sv_aid = agent_pers.sv_p_uid) LEFT JOIN agent_stat ON agent_pers.sv_p_uid = agent_stat.sv_s_uid) LEFT JOIN agent_pro ON agent_pers.sv_p_pid=agent_pro.p_id WHERE MONTH(agent_pers.sv_p_datum) =7 GROUP BY sv_aname so the problem is now that i dont want sold items from previous months to get included in the data received, i know i could solve that by simple adding in the WHERE part MONTH(agent_stat.sv_s_datum) =7 but then if no items been sold that month no data at all will show up not the time or anything. Any aid on how i could solve this is greatly appreciated. if there's something that's not so clear dont hesitate to ask and ill try my best to answer. after all my english isn't the best out there :P regards breezer

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