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  • Entity Framework: insert with one-to-one reference

    - by bomortensen
    Hi 'overflow! I'm having a bit trouble inserting into a mssql database using Entity Framework. There's two tables that I want to insert into, where one of table 1s fields is a foreign key in table2. This is the code I have so far: Media media = null; foreach(POI p in poiList) { media = new Media() { Path = p.ImagePath, Title = p.Title }; if (media != null && !context.Media.Any(me => me.Title == p.ImageTitle)) { context.AddToMedia(media); context.SaveChanges(); } PointOfInterest poi = new PointOfInterest() { Altitude = 2000.0, ID = p.ID, Latitude = p.Latitude, Longitude = p.Longitude, LatitudeRoute = p.LatitudeRoute, LongitudeRoute = p.LongitudeRoute, Description = p.Description, Title = p.Title, DefaultImageID = media.ID, }; context.AddToPointOfInterest(poi); } context.SaveChanges(); The following gives me this error: An object with the same key already exists in the ObjectStateManagerAn object with the same key already exists in the ObjectStateManager I'm still learning how to use the entity framework, so I don't even know if this would be the right approach to insert into two referenced tables. Can anyone enlighten me on this? :) Any help would be greatly appreciated! Thanks!

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  • C# WPF XAML binding to DataTable

    - by LnDCobra
    I have the following tables: Company {CompanyID, CompanyName} Deal {CompanyID, Value} And I have a listbox: <ListBox Name="Deals" Height="100" Width="420" Margin="0,20,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" Visibility="Visible" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding}" SelectionChanged="Deals_SelectionChanged"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal"> <TextBlock Text="{Binding companyRowByBuyFromCompanyFK.CompanyName}" FontWeight="Bold" /> <TextBlock Text=" -> TGS -> " /> <TextBlock Text="{Binding BuyFrom}" FontWeight="Bold" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> As you can see, I want to display the CompanyName rather then the ID which is a foreign Key. The relation "companyRowByBuyFromCompanyFK" exists, as in Deals_SelectionChanged I can access companyRowByBuyFromCompanyFK property of the Deals row, and I also can access the CompanyName propert of that row. Is the reason why this is not working because XAML binding uses the [] indexer? Rather than properties on the CompanyRows in my DataTable? At the moment im getting values such as - TGS - 3 - TGS - 4 What would be the best way to accomplish this? Make a converter to convert foreign keys using Table being referenced as custom parameter. Create Table View for each table? This would be long winded as I have quite a large number of tables that have foreign keys.

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  • UML class diagram vs ER database diagram

    - by salva84
    Hi, I'm a little confused, I'm developing a program, the program consist in two parts, the server and the clients, there are groups, places, messages... stored in the server, and the clients has to connect with it. I've design the use cases diagram, the activity diagrams, and I have design the class diagram too. The thing is that I want to implement the server in a mysql tables for storing the users, groups, places... users in groups... so I've designed a E-R diagram consisting in 6 tables, but the problem is that I think that my class diagram and my ER diagram looks too similar, I mean, I think I'm not doing things right because I have a class for each table practically, and when I have to extract all the users on my system, do I have to convert all the rows into objects at first and write in the database for each object modified? The easy choice for me would be to base my whole application only in the database, and making a class to extract and insert data in it, but I have to follow the UML specification and I'm a little confused what to do with the class diagram, because the books I have read say that I have to create a class for each "entity" of my program. Sorry for my bad English. Thank you.

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  • Find Port Number and Domain Name to connect to Hive Table

    - by user1419563
    I am new to Hive, MapReduce and Hadoop. I am using Putty to connect to hive table and access records in the tables. So what I did is- I opened Putty and in the host name I typed- ares-ingest.vip.host.com and then I click Open. And then I entered my username and password and then few commands to get to Hive sql. Below is the list what I did $ bash bash-3.00$ hive Hive history file=/tmp/rjamal/hive_job_log_rjamal_201207010451_1212680168.txt hive> set mapred.job.queue.name=hdmi-technology; hive> select * from table LIMIT 1; So my question is- I was trying to connect to Hive Tables using Squirrel SQL Client, so in that my Connection URL is- jdbc:hive://ares-ingest.vip.host.com:10000/default. So whenever I try to connect with these attributes, I always get Hive: Could not establish connection to ares-ingest.vip.host.com:10000/default: java.net.ConnectException: Connection timed out: connect. It might be possible I am using wrong port number or domain name here. Is there any way from the command prompt I can find out these two things, like what Domain Name and Port Number(where Hive server is running) should I use to connect to Hive table from Squirrel SQL Client. As I know host and port are determined by where the hive server is running

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  • Django: Unicode Filenames with ASCII headers?

    - by TheLizardKing
    I have a list of strangely encoded files: 02 - Charlie, Woody and You/Study #22.mp3 which I suppose isn't so bad but there are a few particular characters which Django OR nginx seem to be snagging on. >>> test = u'02 - Charlie, Woody and You/Study #22.mp3' >>> test u'02 - Charlie, Woody and You\uff0fStudy #22.mp3' I am using nginx as a reverse proxy to connect to django's built in webserver (still in development stages) and postgresql for my database. My database and tables are all en_US.UTF-8 and I am using pgadmin3 to view my tables outside of django. My issue goes a little beyond my title, firstly how should I be saving possibly whacky filenames in my database? My current method is 'path': smart_unicode(path.lstrip(MUSIC_PATH)), 'filename': smart_unicode(file) and when I pprint out the values they do show u'whateverthecrap' I am not sure if that is how I should be doing it but assuming it is now I have issues trying to spit out the download. My download view looks something like this: def song_download(request, song_id): song = get_object_or_404(Song, pk=song_id) url = u'/static_music/%s/%s' % (song.path, song.filename) print url response = HttpResponse() response['X-Accel-Redirect'] = url response['Content-Type'] = 'audio/mpeg' response['Content-Disposition'] = "attachment; filename=test.mp3" return response and most files will download but when I get to 02 - Charlie, Woody and You/Study #22.mp3 I receive this from django: 'ascii' codec can't encode character u'\uff0f' in position 118: ordinal not in range(128), HTTP response headers must be in US-ASCII format. How can I use an ASCII acceptable string if my filename is out of bounds? 02 - Charlie, Woody and You\uff0fStudy #22.mp3 doesn't seem to work... EDIT 1 I am using Ubuntu for my OS.

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  • Good DB Migrations for CakePHP?

    - by Martin Westin
    Hi, I have been trying a few migration scripts for CakePHP but I ran into problems with all of the in some form or another. Please advice me on a migration option for Cake that you use live and know works. I'd like the following "features": -Support CakePHP 1.2(e.g. CakeDCs migrations will only be an option when 1.3 is stable and my app migrated to the new codebase) -Support for (or at least not halt on) Models with a different database config. -Support Models in sub-folders of app/models -Support Models in plugins -Support tables that do not conform to Cake conventions (I have a few special tables that do not have a single primary key field and need to keep them) -Plays well with automated deployment via Capistrano and Git. I do not need rails-style versioned files a git versioned schema file that is compared live to the existing schema will do. That is: I like the SchemaShell in Cake apart from it not being compatible with most of my requirements above. I have looked at and tested: CakePHP Schema Shell http://book.cakephp.org/view/734/Schema-management-and-migrations CakeDC migrations http://cakedc.com/downloads/view/cakephp_migrations_plugin YAML migrations http://github.com/georgious/cakephp-yaml-migrations-and-fixtures joelmoss migrations http://code.google.com/p/cakephp-migrations

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  • Oracle command hangs when using view for "WHERE x IN..." subquery

    - by Calvin Fisher
    I'm working on a web service that fetches data from an oracle data source in chunks and passes it back to an indexing/search tool in XML format. I'm the C#/.NET guy, and am kind of fuzzy on parts of Oracle. Our Oracle team gave us the following script to run, and it works well: SELECT ROWID, [columns] FROM [table] WHERE ROWID IN ( SELECT ROWID FROM ( SELECT ROWID FROM [table] WHERE ROWID > '[previous_batch_last_rowid]' ORDER BY ROWID ) WHERE ROWNUM <= 10000 ) ORDER BY ROWID 10,000 rows is an arbitrary but reasonable chunk size and ROWID is sufficiently unique for our purposes to use as a UID since each indexing run hits only one table at a time. Bracketed values are filled in programmatically by the web service. Now we're going to start adding views to the indexing, each of which will union a few separate tables. Since ROWID would no longer function as a unique identifier, they added a column to the views (VIEW_UNIQUE_ID) that concatenates the ROWIDs from the component tables to construct a UID for each union. But this script does not work, even though it follows the same form as the previous one: SELECT VIEW_UNIQUE_ID, [columns] FROM [view] WHERE VIEW_UNIQUE_ID IN ( SELECT VIEW_UNIQUE_ID FROM ( SELECT VIEW_UNIQUE_ID FROM [view] WHERE ROWID > '[previous_batch_last_view_unique_id]' ORDER BY VIEW_UNIQUE_ID ) WHERE ROWNUM <= 10000 ) ORDER BY VIEW_UNIQUE_ID It hangs indefinitely with no response from the Oracle server. I've waited 20+ minutes and the SQLTools dialog box indicating a running query remains the same, with no progress or updates. I've tested each subquery independently and each works fine and takes a very short amount of time (<= 1 second), so the view itself is sound. But as soon as the inner two SELECT queries are added with "WHERE VIEW_UNIQUE_ID IN...", it hangs. Why doesn't this query work for views? In what important way are they not interchangeable here?

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  • Ado JobStore use!

    - by aleo
    well i'm new in Quartz i'm following this tutorial and i configured my scheduler instance and quartz to use this properties: properties["quartz.jobStore.lockHandler.type"] = "Quartz.Impl.AdoJobStore.UpdateLockRowSemaphore, Quartz"; properties["quartz.jobStore.driverDelegateType"] = "Quartz.Impl.AdoJobStore.SqlServerDelegate, Quartz"; properties["quartz.jobStore.dataSource"] = "default"; properties["quartz.dataSource.default.connectionString"] = "Server=loclahost;Initial Catalog=aleo;Persist Security Info=True;User ID=userid;Password=password"; properties["quartz.dataSource.default.provider"] = "SqlServer-20"; properties["quartz.jobStore.type"] = "Quartz.Impl.AdoJobStore.JobStoreTX, Quartz"; properties["quartz.jobStore.useProperties"] = "true"; properties["quartz.jobStore.tablePrefix"] = "QRTZ_"; ISchedulerFactory schedFact = new Quartz.Impl.StdSchedulerFactory(properties); IScheduler sched = schedFact.GetScheduler(); sched.Start(); but what's next? i am new on C# but if someone explain to can understand :) and my question are how i will add jobs and triggers and stuff to the database? i also created the tables given in the Database/tables folder that comes with Quartz API thanks.

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  • is it possible to add DataRelation to DataSet if child table contains rows that have no parent in pa

    - by matti
    If I fill the DataSet with DataAdapters that select all rows from Orders and Customers and call: private void CreateRelation() { // Get the DataColumn objects from two DataTable objects // in a DataSet. Code to get the DataSet not shown here. DataColumn parentColumn = DataSet1.Tables["Customers"].Columns["CustID"]; DataColumn childColumn = DataSet1.Tables["Orders"].Columns["CustID"]; // Create DataRelation. DataRelation relCustOrder; relCustOrder = new DataRelation("CustomersOrders", parentColumn, childColumn); // Add the relation to the DataSet. DataSet1.Relations.Add(relCustOrder); } (from http://msdn.microsoft.com/en-us/library/system.data.datarelation.aspx) there will be a runtime error if there is orders that do not have customers. This might happen when a buggy program has not deleted customer's orders when customer was deleted. What can I do except put Orders select string a additional where-condition: CUSTID IN (SELECT DISTINCT CUSTID FROM CUSTOMERS) OR: is it really that way (that all children have to have parents)? My code might have a bug also. The exception occurs when IN MY CODE I add the relation to filled DataSet. The exception is: An unhandled exception of type 'System.ArgumentException' occurred in System.Data.dll Additional information: This constraint cannot be enabled as not all values have corresponding parent values. Thanks & Best Regards - Matti

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  • Need Advice on building the database. all in one table or split?

    - by Ibrahim Azhar Armar
    hello, i am developing an application for a real-estate company. the problem i am facing is about implementing the database. however i am just confused on which way to adopt i would appreciate if you could help me out in reasoning the database implementation. here is my situation. a) i have to store the property details in the database. b) the properties have approximately 4-5 categories to which it will belong for ex : resedential, commnercial, industrial etc. c) now the categories have sub-categories. for example. a residential category will have sub category such as. Apartment / Independent House / Villa / Farm House/ Studio Apartment etc. and hence same way commercial and industrial or agricultural will too have sub-categories. d) each sub-categories will have to store the different values. like a resident will have features like Bedrooms/ kitchens / Hall / bathroom etc. the features depends on the sub categories. for an example on how i would want to implement my application you can have a look at this site. http://www.magicbricks.com/bricks/postProperty.html i could possibly think of the solution like this. a) create four to five tables depending upon the categories which will be existing(the problem is categories might increase in the future). b) create different tables for all the features, location, price, description and merge the common property table into one. for example all the property will have the common entity such as location, total area, etc. what would you advice for me given the current situation. thank you

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  • Factory pattern vs ease-of-use?

    - by Curtis White
    Background, I am extending the ASP.NET Membership with custom classes and extra tables. The ASP.NET MembershipUser has a protected constructor and a public method to read the data from the database. I have extended the database structure with custom tables and associated classes. Instead of using a static method to create a new member, as in the original API: I allow the code to instantiate a simple object and fill the data because there are several entities. Original Pattern #1 Protected constructor > static CreateUser(string mydata, string, mydata, ...) > User.Data = mydata; > User.Update() My Preferred Pattern #2 Public constructor > newUser = new MembershipUser(); > newUser.data = ... > newUser.ComplextObject.Data = ... > newUser.Insert() > newUser.Load(string key) I find pattern #2 to be easier and more natural to use. But method #1 is more atomic and ensured to contain proper data. I'd like to hear any opinions on pros/cons. The problem in my mind is that I prefer a simple CRUD/object but I am, also, trying to utilize the underlying API. These methods do not match completely. For example, the API has methods, like UnlockUser() and a readonly property for the IsLockedOut

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  • MySQL Connector for .NET - Is it REALLY mature?

    - by effkay
    After spending a miserable month with MySQL/.NET/EntityFramework, my findings: Support for Entity Framework is VERY primitive, please use it for student-subjects type of database. Kindly do not consider it using for serious development as they ARE STILL unable to sort out VERY BASIC things like: it DOES NOT support unsigned stuff it DOES NOT support unsigned columns as FK; if you try, it gives you a beautiful exception; "The specified value is not an instance of a valid constant type\r\nParameter name: value" [http://bugs.mysql.com/bug.php?id=44801] blob cannot store more then few KB; cannot compare null object with a column with a LEGAL null value [http://bugs.mysql.com/bug.php?id=49936] they are unable to write VERY PRIMITIVE check to return date as null if value in column is 0000-00-00 00:00:00 if you use Visual Studio; sorry; mysql/sun guys hate Microsoft, they will NOT LET you import more then two or three tables (for Micky Mouse type of tables, they allow five; but thats it) - if you try, it will throw TIME OUT error on your face ... unless you are smart enough to change the connection time in connection string Anyone who would like to add in above list? WISH I would have seen a list like this before I selected MySQL :(

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  • Modeling a Generic Relationship in a Database

    - by StevenH
    This is most likely one for all you sexy DBAs out there: How would I effieciently model a relational database whereby I have a field in an "Event" table which defines a "SportType". This "SportsType" field can hold a link to different sports tables E.g. "FootballEvent", "RubgyEvent", "CricketEvent" and "F1 Event". Each of these Sports tables have different fields specific to that sport. My goal is to be able to genericly add sports types in the future as required, yet hold sport specific event data (fields) as part of my Event Entity. Is it possible to use an ORM such as NHibernate / Entity framework which would reflect such a relationship? I have thrown together a quick C# example to express my intent at a higher level: public class Event<T> where T : new() { public T Fields { get; set; } public Event() { EventType = new T(); } } public class FootballEvent { public Team CompetitorA { get; set; } public Team CompetitorB { get; set; } } public class TennisEvent { public Player CompetitorA { get; set; } public Player CompetitorB { get; set; } } public class F1RacingEvent { public List<Player> Drivers { get; set; } public List<Team> Teams { get; set; } } public class Team { public IEnumerable<Player> Squad { get; set; } } public class Player { public string Name { get; set; } public DateTime DOB { get; set;} }

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  • NHibernate HiLo generation and SQL 2005/8 Schemas

    - by Kirk Clawson
    I have an issue on my hands that I've spent several days searching for an answer to no avail... We're using HiLo Id generation, and everything seems to be working fine, as long as the entity table is in the same schema as the hibernate_unique_key table. The table structure is pretty simple. I have my hi value table in the db as dbo.hibernate_unique_key. Several entity table are also in the dbo schema, and they work without issue. Then we have tables under the "Contact" schema (such as Contact.Person and Contact.Address). In the Person Mapping file: <class name="Person" table="Person" schema="Contact"> <id name="Id" unsaved-value="0"> <generator class="hilo"> <param name="max_lo">100</param> </generator> </id> ... When I try to insert a Person entity, I get an error of "Invalid object name 'Contact.hibernate_unique_key'. That error is certainly clear enough. So I add: <param name="schema">dbo</param> to my mapping file/generator element. Now, when the SessionFactory is built, I get a "An item with the same key has already been added." error. So now I'm a bit stuck. I can't leave the HiLo generator without a schema, because it picks up the schema from the Class, and I can't specify the schema because it's already been added (presumably because it's my "default_schema" as identified in my XML cfg file). Am I completely hosed here? Must I either A) Keep all my tables in the dbo schema or B) Create a separate HiLo Key table for each unique schema in the DB? Neither of those scenarios is particularly palatable for my application, so I'm hoping that I can "fix" my mapping files to address this issue.

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  • What is your best-practice advice on implementing SQL stored procedures (in a C# winforms applicatio

    - by JYelton
    I have read these very good questions on SO about SQL stored procedures: When should you use stored procedures? and Are Stored Procedures more efficient, in general, than inline statements on modern RDBMS’s? I am a beginner on integrating .NET/SQL though I have used basic SQL functionality for more than a decade in other environments. It's time to advance with regards to organization and deployment. I am using .NET C# 3.5, Visual Studio 2008 and SQL Server 2008; though this question can be regarded as language- and database- agnostic, meaning that it could easily apply to other environments that use stored procedures and a relational database. Given that I have an application with inline SQL queries, and I am interested in converting to stored procedures for organizational and performance purposes, what are your recommendations for doing so? Here are some additional questions in my mind related to this subject that may help shape the answers: Should I create the stored procedures in SQL using SQL Management Studio and simply re-create the database when it is installed for a client? Am I better off creating all of the stored procedures in my application, inside of a database initialization method? It seems logical to assume that creating stored procedures must follow the creation of tables in a new installation. My database initialization method creates new tables and inserts some default data. My plan is to create stored procedures following that step, but I am beginning to think there might be a better way to set up a database from scratch (such as in the installer of the program). Thoughts on this are appreciated. I have a variety of queries throughout the application. Some queries are incredibly simple (SELECT id FROM table) and others are extremely long and complex, performing several joins and accepting approximately 80 parameters. Should I replace all queries with stored procedures, or only those that might benefit from doing so? Finally, as this topic obviously requires some research and education, can you recommend an article, book, or tutorial that covers the nuances of using stored procedures instead of direct statements?

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  • How do you determine subtype of an entity using Inheritance with Entity Framework 4?

    - by KallDrexx
    I am just starting to use the Entity Framework 4 for the first time ever. So far I am liking it but I am a bit confused on how to correctly do inheritance. I am doing a model-first approach, and I have my Person entity with two subtype entities, Employee and Client. EF is correctly using the table per type approach, however I can't seem to figure out how to determine what type of a Person a specific object is. For example, if I do something like var people = from p in entities.Person select p; return people.ToList<Person>(); In my list that I form from this, all I care about is the Id field so i don't want to actually query all the subtype tables (this is a webpage list with links, so all I need is the name and the Id, all in the Persons table). However, I want to form different lists using this one query, one for each type of person (so one list for Clients and another for Employees). The issue is if I have a Person entity, I can't see any way to determine if that entity is a Client or an Employee without querying the Client or Employee tables directly. How can I easily determine the subtype of an entity without performing a bunch of additional database queries?

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  • Joining on a common table, how do you get a FULL OUTER JOIN to expand on another table?

    - by stimpy77
    I've scoured StackOverflow and Google for an answer to this problem. I'm trying to create a Microsot SQL Server 2008 view. Not a stored procedure. Not a function. Just a query (i.e. a view). I have three tables. The first table defines a common key, let's say "CompanyID". The other two tables have a sometimes-common field, let's say "EmployeeName". I want a single table result that, when my WHERE clause says "WHERE CompanyID = 12" looks like this: CompanyID | TableA | TableB 12 | John Doe | John Doe 12 | Betty Sue | NULL 12 | NULL | Billy Bob I've tried a FULL OUTER JOIN that looks like this: SELECT Company.CompanyID, TableA.EmployeeName, TableB.EmployeeName FROM Company FULL OUTER JOIN TableA ON Company.CompanyID = TableA.CompanyID FULL OUTER JOIN TableB ON Company.CompanyID = TableB.CompanyID AND (TableA.EmployeeName IS NULL OR TableB.EmployeeName IS NULL OR TableB.EmployeeName = TableA.EmployeeName) I'm only getting the NULL from one matched table, I'm not getting the expansion for the other table. In the above sample, I'm basically only getting the first and third rows and not the second. Can someone help me create this query and show me how this is done correctly? BTW I already have a stored procedure that looks very clean and populates an in-memory table, but that isn't what I want. Thanks.

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  • SQL Server 2008 Running trigger after Insert, Update locks original table

    - by Polity
    Hi Folks, I have a serious performance problem. I have a database with (related to this problem), 2 tables. 1 Table contains strings with some global information. The second table contains the string stripped down to each individual word. So the string is like indexed in the second table, word by word. The validity of the data in the second table is of less important then the validity of the data in the first table. Since the first table can grow like towards 1*10^6 records and the second table having an average of like 10 words for 1 string can grow like 1*10^7 records, i use a nolock in order to read the second this leaves me free for inserting new records without locking it (Expect many reads on both tables). I have a script which keeps on adding and updating rows to the first table in a MERGE statement. On average, the data beeing merged are like 20 strings a time and the scripts runs like ones every 5 seconds. On the first table, i have a trigger which is beeing invoked on a Insert or Update, which takes the newly inserted or updated data and calls a stored procedure on it which makes sure the data is indexed in the second table. (This takes some significant time). The problem is that when having the trigger disbaled, Reading the first table happens in a few ms. However, when enabling the trigger and your in bad luck of trying to read the first table while this is beeing updated, Our webserver gives you a timeout after 10 seconds (which is way to long anyways). I can quess from this part that when running the trigger, the first table is kept (partially) in a lock untill the trigger is completed. What do you think, if i'm right, is there a easy way around this? Thanks in advance! Cheers, Koen

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  • Easy way to observe user activity - how improve my database structure.

    - by Thomas
    Welcome, I need some advise to improve perfomence my web application. In the begin I had this structure of database: USER -id (Primary Key) -name -password -email .... PROFILE -user Primary Key, Foreign Key (USER) -birthday -region -photoFile ... PAGES -id (Primary Key) -user Foreign Key(USER) -page -date COMMENTS -id (Primary Key) -user Foreign Key(USER) -page Foreign Key(PAGE) -comment -date FAVOURITES_PAGES -id (Primary Key) -user Foreign Key(USER) -favourite_page Foreign Key(PAGE) -date but now one of the most important page of website is observatory, when everyone can observe activity others users. So I need select all pages, comments and favourites pages some users and display it in one list, sorted by date. For better perfomance (I think) I changed my structure to this: table USER and PROFILE without changes ACTIVITY (additional table- have common fields: user,date) -id (Primary Key) -user Foreign Key(USER) -date -page Foreign Key(PAGE) -comment Foreign Key(COMMENTS) -favourite_page Foreign Key(FAVOURITES_PAGES) PAGES -id (Primary Key) -page COMMENTS -id (Primary Key) -page Foreign Key(PAGE) -comment FAVOURITES_PAGES -id (Primary Key) -favourite_page Foreign Key(PAGE) So now it is very easy get sorted records from all tables. But I have no only foreign key to PAGES, COMMENTS and FAVOURITES_PAGES in ACTIVITY table - there is about ten Foreign Key fields and in one record only one have value, others have None: ACTIVITY id user date page comment ... 1 2 2010-02-23 None 1 2 1 2010-02-21 1 None .... It is corect solution. When I display about 40 records in one page (pagination) I must wait about one secound, but database is almost emty (a few users and about 100 records in others tables). It is depends on amount records per page - I have checked it, but why it takes too long time, becouse of relationships? The website is built in Python/Django. Any advices/opinion?

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  • Complex SQL query... names of returned variables

    - by Andrew P.
    Excuse me for what I'm sure is an elementary question for most of you, but I have an issue with table columns from separate tables having the same name as one another, and trying to select from both tables in the same query. Okay, so this is my code: $q_value = $mdb2->quote($_POST['query']); $field = $_POST['field']; $sql = "SELECT m.*, l.name FROM memberlist m, mail_lists l WHERE m.$field=$q_value AND l.id = m.list ORDER BY m.id"; $l_list = $mdb2->queryAll($sql, '', 'MDB2_FETCHMODE_ASSOC'); The table memberlist has the following columns: id, email, list, sex, name and the table mail_lists has the following columns: id, name After running the query, I later loop through the results with a foreach like so: foreach ($l_list as $l){ //blahblah } The problem is that the column 'name' in mail_lists refers to the names of the list, while the column 'name' in memberlist refers to the name of the member. When I later access $l-name (within the foreach), will I get m.name, or l.name? Furthermore, how do I get access to the other? Or will I just have to do two separate queries?

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  • Retrieve 2 last posts for each category.

    - by Savageman
    Hello, Lets say I have 2 tables: blog_posts and categories. Each blog post belongs to only ONE category, so there is basically a foreign key between the 2 tables here. I would like to retrieve the 2 lasts posts from each category, is it possible to achieve this in a single request? GROUP BY would group everything and leave me with only one row in each category. But I want 2 of them. It would be easy to perform 1 + N query (N = number of category). First retrieve the categories. And then retrieve 2 posts from each category. I believe it would also be quite easy to perform M queries (M = number of posts I want from each category). First query selects the first post for each category (with a group by). Second query retrieves the second post for each category. etc. I'm just wondering if someone has a better solution for this. I don't really mind doing 1+N queries for that, but for curiosity and general SQL knowledge, it would be appreciated! Thanks in advance to whom can help me with this.

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  • Using datetime float representation as primary key

    - by devanalyst
    From my experience I have learn that using an surrogate INT data type column as primary key esp. an IDENTITY key column offers better performance than using GUID or char/varchar data type column as primary key. I try to use IDENTITY key as primary key wherever possible. But recently I came across a schema where the tables were horizontally partitioned and were managed via a Partitioned view. So the tables could not have an IDENTITY column since that would make the Partitioned View non updatable. One work around for this was to create a dummy 'keygenerator' table with an identity column to generate IDs for primary key. But this would mean having a 'keygenerator' table for each of the Partitioned View. My next thought was to use float as a primary key. The reason is the following key algorithm that I devised DECLARE @KEY FLOAT SET @KEY = CONVERT(FLOAT,GETDATE())/100000.0 SET @KEY = @EMP_ID + @KEY Heres how it works. CONVERT(FLOAT,GETDATE()) gives float representation of current datetime since internally all datetime are represented by SQL as a float value. CONVERT(FLOAT,GETDATE())/100000.0 converts the float representation into complete decimal value i.e. all digits are pushed to right side of ".". @KEY = @EMP_ID + @KEY adds the Employee ID which is an integer to this decimal value. The logic is that the Employee ID is guaranteed to be unique across sessions since an employee cannot connect to an application more than once at the same time. And for the same employee each time a key will be generated the current datetime will be unique. In all an unique key across all employee sessions and across time. So for Emp Ids 11 and 12, I have key values like 12.40046693321566357, 11.40046693542361111 But my concern whether float data type as primary key offer benefits compared to choosing GUID or char/varchar as primary keys. Also important thing is because of partitioning the float column is going to be part of a composite key.

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  • edmx - The operation could not be completed - After adding Inheritance

    - by vdh_ant
    Hey guys I have an edmx model which I have draged 2 tables onto - One called 'File' and the other 'ApplicaitonFile'. These two tables have a 1 to 1 relationship in the database. If I stop here everything works fine. But in my model, I want 'ApplicaitonFile' to inherit from 'File'. So I delete the 1 to 1 relationship then configure 'ApplicaitonFile' from 'File' and then remove the FileId from 'ApplicaitonFile' which was the primary key. (Note I am following the instructions from here). If I leave the model open at this point everything is fine, but as soon as I close it, if I try and reopen it again I get the following error "The operation could not be completed". I have been searching for a solution and found this - http://stackoverflow.com/questions/944050/entity-model-does-not-load but as far as I can tell I don't have a duplicate InheritanceConnectors (although I don't know exactly what I'm looking for but I can't see anything out of the ordinary - like 2 connectors with the same name) and the relationship I originally have is a 1 to 1 not a 1 to 0..1 Any ideas???

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  • Using a .MDF SQL Server Database with ASP.NET Versus Using SQL Server

    - by Maxim Z.
    I'm currently writing a website in ASP.NET MVC, and my database (which doesn't have any data in it yet, it only has the correct tables) uses SQL Server 2008, which I have installed on my development machine. I connect to the database out of my application by using the Server Explorer, followed by LINQ to SQL mapping. Once I finish developing the site, I will move it over to my hosting service, which is a virtual hosting plan. I'm concerned about whether using the SQL Server setup that is currently working on my development machine will be hard to do on the production server, as I'll have to import all the database tables through the hosting control panel. I've noticed that it is possible to create a SQL Server database from inside Visual Studio. It is then stored in the App_Data directory. My questions are the following: Does it make sense to move my SQL Server DB out of SQL Server and into the App_Data directory as an .mdf file? If so, how can I move it? I believe this is called the Detach command, is it not? Are there any performance/security issues that can occur with a .mdf file like this? Would my intended setup work OK with a typical virtual hosting plan? I'm hoping that the .mdf database won't count against the limited number of SQL Server databases that can be created with my plan. I hope this question isn't too broad. Thanks in advance! Note: I'm just starting out with ASP.NET MVC and all this, so I might be completely misunderstanding how this is supposed to work.

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  • SQL Server 2005 standard filegroups / files for performance on SAN

    - by Blootac
    Ok so I've just been on a SQL Server course and we discussed the usage scenarios of multiple filegroups and files when in use over local RAID and local disks but we didn't touch SAN scenarios so my question is as follows; I currently have a 250 gig database running on SQL Server 2005 where some tables have a huge number of writes and others are fairly static. The database and all objects reside in a single file group with a single data file. The log file is also on the same volume. My interpretation is that separate data files should be used across different disks to lessen disk contention and that file groups should be used for partitioning of data. However, with a SAN you obviously don't really have the same issue of disk contention that you do with a small RAID setup (or at least we don't at the moment), and standard edition doesn't support partitioning. So in order to improve parallelism what should I do? My understanding of various Microsoft publications is that if I increase the number of data files, separate threads can act across each file separately. Which leads me to the question how many files should I have. One per core? Should I be putting tables and indexes with high levels of activity in separate file groups, each with the same number of data files as we have cores? Thank you

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