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• Virtual Function Implementation

  - by Gokul

  Hi, I have kept hearing this statement. Switch..Case is Evil for code maintenance, but it provides better performance(since compiler can inline stuffs etc..). Virtual functions are very good for code maintenance, but they incur a performance penalty of two pointer indirections. Say i have a base class with 2 subclasses(X and Y) and one virtual function, so there will be two virtual tables. The object has a pointer, based on which it will choose a virtual table. So for the compiler, it is more like switch( object's function ptr ) { case 0x....: X->call(); break; case 0x....: Y->call(); }; So why should virtual function cost more, if it can get implemented this way, as the compiler can do the same in-lining and other stuff here. Or explain me, why is it decided not to implement the virtual function execution in this way? Thanks, Gokul.

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• SQL Server 2008 automated database drop, create and fill

  - by lox

  For the database in my project I have a drop/create script for the database, a script for creating tables and SPs and an Access 2003 .mdb file with some exported values. To set up the database from scratch I can use my SQL management studio to first run one script, then the other and lastly manually run the sort of tedious import task. But I would like to do this as automated as possible. Hopefully something like putting the three files in a folder along with a fourth script to execute. Looking something like: run script "dropcreate.sql" run script "createtables.sql" import "values.mdb" How is this done? I hope to avoid using SSIS and the like. The tricky this is of course the import of data, where I can't seem to find a simple way. It is also important that the files a left as they are and not embedded into anything.

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• Should I specify both INDEX and UNIQUE INDEX?

  - by Matt Huggins

  On one of my PostgreSQL tables, I have a set of two fields that will be defined as being unique in the table, but will also both be used together when selecting data. Given this, do I only need to define a UNIQUE INDEX, or should I specify an INDEX in addition to the UNIQUE INDEX? This? CREATE UNIQUE INDEX mytable_col1_col2_idx ON mytable (col1, col2); Or this? CREATE UNIQUE INDEX mytable_col1_col2_uidx ON mytable (col1, col2); CREATE INDEX mytable_col1_col2_idx ON mytable (col1, col2);

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• Preview result of update/insert query whithout comitting changes to database in MySQL?

  - by Camsoft

  I am writing a script to import CSV files into existing tables within my database. I decided to do the insert/update operations myself using PHP and INSERT/UPDATE statements, and not use MySQL's LOAD INFILE command, I have good reasons for this. What I would like to do is emulate the insert/update operations and display the results to the user, and then give them the option of confirming that this is OK, and then committing the changes to the database. I'm using InnoDB database engine with support for transactions. Not sure if this helps but was thinking down the line of insert/update, query data, display to user, then either commit or rollback transaction? Any advise would be appreciated.

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• SQL server 2005 remote connection problem, cannot solve it help please thank you

  - by user287745

  note:- if this question does not fit this site please do not just close it but also redirect the question to the fitting sister site, thank you" the steps taken and the error are mentioned please help, i am stuck here! installed sql server 2005 express on both computers installed sql server management studio express on both computers ran each management studio and connect to instance sqlserver using windows authentication ( one computer connection example "A-63A9D4D7E7834\SQLEXPRESS" ) created a database in the databases named as "test1" created a few tables with data saved and exit. did everything what this site says " How to configure SQL Server 2005 to allow remote connections" [add h t t p here as spam prevention] ://support.microsoft.com/kb/914277/en-us" but i have just disable the firewalls completely :turn off connecting to A-63A9D4D7E7834 started "SQL Server Management Studio Express" on computer A-63A9D4D7E7834 sever name: "ALL-E425BE6C41D\SQLEXPRESS" authentication: "windows authentication" and CONNECT I GET THE FOLLOWING ERROR Cannot connect to ALL-E425BE6C41D\SQLEXPRESS. ADDITIONAL INFORMATION: Login failed for user 'ALL-E425BE6C41D\Guest'. (Microsoft SQL Server, Error: 18456) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=18456&LinkId=20476 BUTTONS: OK HELP

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• SQL Complicated Group / Join by Category

  - by Mike Silvis

  I currently have a database structure with two important tables. 1) Food Types (Fruit, Vegetables, Meat) 2) Specific Foods (Apple, Oranges, Carrots, Lettuce, Steak, Pork) I am currently trying to build a SQL statement such that I can have the following. Fruit < Apple, Orange Vegetables < Carrots, Lettuce Meat < Steak, Port I have tried using a statement like the following Select * From Food_Type join (Select * From Foods) as Foods on Food_Type.Type_ID = Foods.Type_ID but this returns every Specific Food, while I only want the first 2 per category. So I basically need my subquery to have a limit statement in it so that it finds only the first 2 per category. However if I simply do the following Select * From Food_Type join (Select * From Foods LIMIT 2) as Foods on Food_Type.Type_ID = Foods.Type_ID My statement only returns 2 results total.

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• How to optimise MySQL query containing a subquery?

  - by aidan

  I have two tables, House and Person. For any row in House, there can be 0, 1 or many corresponding rows in Person. But, of those people, a maximum of one will have a status of "ACTIVE", the others will all have a status of "CANCELLED". e.g. SELECT * FROM House LEFT JOIN Person ON House.ID = Person.HouseID House.ID | Person.ID | Person.Status 1 | 1 | CANCELLED 1 | 2 | CANCELLED 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | 4 | CANCELLED I want to filter out the cancelled rows, and get something like this: House.ID | Person.ID | Person.Status 1 | 3 | ACTIVE 2 | 1 | ACTIVE 3 | NULL | NULL 4 | NULL | NULL I've achieved this with the following sub select: SELECT * FROM House LEFT JOIN ( SELECT * FROM Person WHERE Person.Status != "CANCELLED" ) Person ON House.ID = Person.HouseID ...which works, but breaks all the indexes. Is there a better solution that doesn't? I'm using MySQL and all relevant columns are indexed. EXPLAIN lists nothing in possible_keys. Thanks.

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• DataGridView's SelectionChange event firing more than once on DataBinding

  - by Shantanu Gupta

  This Code triggers selection change event twice. how can I prevent it ? Currently i m using a flag or focused property to prevent this. But what is the actual way ? I am using it on winfoms EDIT Mistake in writing Question, here is the correct code that i wanted to ask private void frmGuestInfo_Load(object sender, EventArgs e) { this.dgvGuestInfo.SelectionChanged -= new System.EventHandler(this.dgvGuestInfo_SelectionChanged); dgvGuestInfo.DataSource=dsFillControls.Tables["tblName"]; this.dgvGuestInfo.SelectionChanged += new System.EventHandler(this.dgvGuestInfo_SelectionChanged); } private void dgvGuestInfo_SelectionChanged(object sender, EventArgs e) { }

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• Can I combine values from multiple rows in another table into multiple columns of one row using SQL?

  - by Jordi

  I have two tables: T1: | M_ID | P_ID1 | P_ID2 | rest of T1 columns | | 0 | 0 | 1 | ... | | 1 | 2 | 3 | ... | T2: | P_ID | Type | A | B | | 0 | 1 | a | e | | 1 | 2 | b | f | | 2 | 1 | c | g | | 3 | 2 | d | h | Now, I want to have a query that selects this: | M_ID | P_1a | P_1b | P_2a | P_2b | rest of T1 columns | | 0 | a | e | b | f | ... | | 1 | c | g | c | h | ... | So, in words: I want to select all columns from T1, but I want to replace P_ID1 with the columns from T2, where the P_ID is equal to P_ID1, and the type is 1, and basically the same for P_ID2. I can obviously get the information I need with multiple queries, but I was wondering if there is a way that I can do this with one query. Any ideas? I'm currently using SQL Server 2008r2, but I'd also be interested in solutions for other database software. Thanks for the help!

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• Core Data => Adding a related object always nil

  - by mongeta

  Hello, I have two tables related: DataEntered and Model DataEntered -currentModel Model One DataEntered can have only ONE Model, but a Model can stay into many DataEntered. The relationship is from DataEntered to Model (No To Many-relathionship) and no inverse relation. XCode generates the setters for DataEnteredModel: @property (nonatomic, retain) NSSet * current_model; - (void)addCurrent_modelObject:(CarModel *)value; - (void)addCurrent_model:(NSSet *)value; I have a Table and when I select a model, I want to store it to DataEntered: Model *model = [fetchedResultsController objectAtIndexPath:indexPath]; NSLog(@"Model %@",model.name); // ==> gives me the correct model name [dataEntered addCurrent_modelObject:model]; // ==> always nil [dataEntered setCurrent_model:[fetchedResultsController objectAtIndexPath:indexPath]]; // the same, always nil what I'm doing wrong ????? thanks, r.

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• Recommendations for an in memory database vs thread safe data structures

  - by yx

  TLDR: What are the pros/cons of using an in-memory database vs locks and concurrent data structures? I am currently working on an application that has many (possibly remote) displays that collect live data from multiple data sources and renders them on screen in real time. One of the other developers have suggested the use of an in memory database instead of doing it the standard way our other systems behaves, which is to use concurrent hashmaps, queues, arrays, and other objects to store the graphical objects and handling them safely with locks if necessary. His argument is that the DB will lessen the need to worry about concurrency since it will handle read/write locks automatically, and also the DB will offer an easier way to structure the data into as many tables as we need instead of having create hashmaps of hashmaps of lists, etc and keeping track of it all. I do not have much DB experience myself so I am asking fellow SO users what experiences they have had and what are the pros & cons of inserting the DB into the system?

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• Complex Join - involving date ranges and sum...

  - by calumbrodie

  I have two tables that I need to join... I want to join table1 and table2 on 'id' - however in table two id is not unique. I only want one value returned for table two, and this value represents the sum of a column called 'total_sold' - within a specified date range (say one month).. SELECT ta.id, tb.total_sold as total_sold_this_week FROM table_a as ta LEFT JOIN table_b as tb ON ta.id=tb.id AND tb.date_sold BETWEEN ADDDATE(NOW(),INTERVAL -3 WEEK) AND NOW() this works but does not SUM the rows - only returning one row for each id... how do I get the sum from table b instead of only one row??? Please criticise if format of question could use more work - I can rewrite and provide sample data if required - this is a trivialised version of a much larger problem. -Thanks

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• Listing mysql row entries from tags into one single row

  - by Derrick

  Hi guys, Ive got two tables, one a listings and another representing a list of tags for the listing table. In the listings table the tag ids are stored in a field called tags as 1-2-3- this has worked out very well for me regular expressions and joins to seperate and display the data, BUT... I now need to pull the titles of those tags into a single row. See below. listings table id tags 1 1-2-3- 2 4-5-6- tags table id title 1 pig 2 dog 3 cat 4 mouse 5 elephant 6 duck And what I need to produce out of the listings table is: id tags 2 mouse, elephant, duck any suggestions?

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• How can I Export a Table in Access using VBA into a specific sheet in an Excel spreadsheet?

  - by Bryan

  I have a some tables, we will call them Table1,Table2.... and I need them to be Exported into specific spreadsheets in a macro enabled Excel File (.xlsm) that already exists. So I would need to put Table1 into Sheet2, Table2 into Sheet3... and so on. I had been doing this manually by going to the export menu in Access but it is getting monotonous so I would like to automate the process. The Excel file will already have code in each spreadsheet which would need to still be intact.

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• how to read the txt file from the database(line by line)

  - by Ranjana

  i have stored the txt file to sql server database . i need to read the txt file line by line to get the content in it. my code : DataTable dtDeleteFolderFile = new DataTable(); dtDeleteFolderFile = objutility.GetData("GetTxtFileonFileName", new object[] { ddlSelectFile.SelectedItem.Text }).Tables[0]; foreach (DataRow dr in dtDeleteFolderFile.Rows) { name = dr["FileName"].ToString(); records = Convert.ToInt32(dr["NoOfRecords"].ToString()); bytes = (Byte[])dr["Data"]; } FileStream readfile = new FileStream(Server.MapPath("txtfiles/" + name), FileMode.Open); StreamReader streamreader = new StreamReader(readfile); string line = ""; line = streamreader.ReadLine(); but here i have used the FileStream to read from the Particular path. but i have saved the txt file in byt format into my Database. how to read the txt file using the byte[] value to get the txt file content, instead of using the Path value.

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• Entity Framework doesn't like 0..1 to * relationships.

  - by Orion Adrian

  I have a database framework where I have two tables. The first table has a single column that is an identity and primary key. The second table contains two columns. One is a nvarchar primary key and the other is a nullable foreign key to the first table. On the default import of the database I get the following error: Condition cannot be specified for Column member 'ForeignKeyId' because it is marked with a 'Computed' or 'Identity' StoreGeneratedPattern. where ForeignKeyId is the second foreign key reference in the second table. Is this just something the entity model doesn't do? Or am I missing something?

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• Domain-driven design with Zend

  - by mik

  This question is a continuation of my previous question here http://stackoverflow.com/questions/2122850/zend-models-architecture (big thanks to Bill Karwin). I've made some reading including this article http://weierophinney.net/matthew/archives/202-Model-Infrastructure.html and this question http://stackoverflow.com/questions/373054/how-to-properly-create-domain-using-zend-framework Now I understand, what domain driven design is. But examples are still very simple and poor. They are based on one table and one model. Now, my question is: do they use Domain Model Design in real-world PHP projects? I've been looking for some good documentation about this, but I haven't found anything good enough, that explains how to manage several tables and transfer them to Domain Objects. As long as I know, there is Hibernate library, that has this features in Java, but what should I use in PHP (Zend Framework)?

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• How to run a loop of queries in access?

  - by tksy

  Hi I have a database with a table which is full of conditions and error messages for checking another database. I want to run a loop such that each of these conditions is checked against all the tables in the second database and generae a report which gives the errors. Is this possible in ms access. For example, querycrit table id query error 1 speed<25 and speed>56 speed above limit 2 dist<56 or dist >78 dist within limit I have more than 400 queries like this of different variables. THe table against which I am running the queries is records table id speed dist accce decele aaa bbb ccc 1 33 34 44 33 33 33 33 2 45 44 55 55 55 22 23 regards ttk

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• MySQL: Count two things in one query?

  - by Nebs

  I have a "boolean" column in one of my tables (value is either 0 or 1). I need to get two counts: The number of rows that have the boolean set to 0 and the number of rows that have it set to 1. Currently I have two queries: One to count the 1's and the other to count the 0's. Is MySQL traversing the entire table when counting rows with a WHERE condition? I'm wondering if there's a single query that would allow two counters based on different conditions? Or is there a way to get the total count along side the WHERE conditioned count? This would be enough as I'd only have to subtract one count from the other (due to the boolean nature of the column). There are no NULL values. Thanks.

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• Groupby in relationtable

  - by Dofs

  I am creating some tag functionality for a forum using linq2sql, and I have two tables [Tag] TagId TagName [ForumTagRelation] TagId ForumId I would like to retrieve, like SO, the most popular tags. I have tried to do this by: List<Tag> popularTags = db.Tags.Select(x => x.ForumTagRelations.GroupBy(y => y.TagId).OrderByDescending(z => z.Count())).Take(count).ToList(); But this just returns the following error: Error 1 Cannot implicitly convert type 'System.Collections.Generic.List<System.Linq.IOrderedEnumerable<System.Linq.IGrouping<System.Guid?,SampleWebsite.ForumTagRelation>>>' to 'System.Collections.Generic.IEnumerable<SampleWebsite.Tag>'. An explicit conversion exists (are you missing a cast?) The question is how I easily can return a list of tags which has the most counts in the ForumTagRelation table?

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• How to set width of textbox to be same as MaxLength in ASP.NET

  - by John Galt

  Is there a way I can limit the width of a textbox to be equal to the MaxLength property? In my case right now, the textbox control is placed in a table cell as in this snippet: <td class=TDSmallerBold style="width:90%"> <asp:textbox id="txtTitle" runat="server" CausesValidation="true" Text="Type a title here..be concise but descriptive. Include price." ToolTip="Describe the item with a short pithy title (most important keywords first). Include the price. The title you provide here will be the primary text found by search engines that index Zipeee content." MaxLength="60" Width="100%"> </asp:textbox> (I know I should not use HTML tables to control layout..another subject for sure) but is there a way to constrain the actual width to the max number of characters allowed in the typed box?

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• Hibernate -using Table per subclass - how to link an existing superclass object to a sibclass object

  - by Chandni

  Hi, I have a User hibernate class, Clerk class and Consumer class. All these maps to their own tables in database. The User PK also acts as Clerk's and Consumer's PK. So now my problem is that if a user is initially a Clerk, he has a record in Users table and Clerks table. If that user wants to become a consumer, I want to link that User's record to the new Consumer's record. So even if I pass the userId to the consumer's record, it treats it as a new User to be persisted and gives a duplicate_key exception. How do I tell Hiernate to link the same user object with this new Consumer object. Thanks in advance, -Chandni

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• Getting mysql row that doesn't conflict with another row

  - by user939951

  I have two tables that link together through an id one is "submit_moderate" and one is "submit_post" The "submit_moderate" table looks like this id moderated_by post 1 James 60 2 Alice 32 3 Tim 18 4 Michael 60 Im using a simple query to get data from the "submit_post" table according to the "submit_moderate" table. $get_posts = mysql_query("SELECT * FROM submit_moderate WHERE moderated_by!='$user'"); $user is the person who is signed in. Now my problem is when I run this query, with the user 'Michael' it will retrieve this 1 James 60 2 Alice 32 3 Tim 18 Now technically this is correct however I don't want to retrieve the first row because 60 is associated with Michael as well as James. Basically I don't want to retrieve that value '60'. I know why this is happening however I can't figure out how to do this. I appreciate any hints or advice I can get.

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• Reading from a oracle temp table in a separate procedure than the one it was populted in

  - by Bob

  I have a 2 stored procedures, the first creates an oracle temp table and the second reads from it. The temp table only has scope for that session. I'm calling the procedures from .Net and the second procedure never returns any results. However if I use the same sprocs and parameters in SQL*Plus it works fine. I've tried creating an Oracle Transaction object and had hoped I'd be able to read the tables in while still using the same transaction - trying to emulate an SQL Plus type of single connection environment. Any ideas what I'm doing wrong??

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• Useful ways for multilanguage navigation and static content on your site?

  - by vitto

  Hi, I have a big site running under Apache and PHP and in few mounths I should consider to add some different language version of it, but I'm not sure about the right way (or ways). My problem it isn't the user data, because I can use db tables with different languages (en, de, it, etc.) so I want concentrate my answer on navigation and static content. For now I can't use gettext because I don't have a dedicated server and I can't reboot it every time I want, but surely will be a future choice. So my main problems are these: In the site, I have classical XHTML elements like the menus, lists, div and various static texts in various pages (should be perferct for gettext, but I need a alternative) The other part of the sites has XHTML elements which are dynamically created via AJAX and jQuery, and here I haven't any idea of what can I do... So does exists some example I can see in some link to solve it (or some useful tecnique)?

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