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• DB design abbreviations

  - by CChriss

  I know PK means primary key and FK means foreign key, but what do "rK" (in section 3) and "PF" (in sections 3, 4, 6, 7, and 8) mean on this page? http://www.databaseanswers.org/tutorial4_data_modelling/index.htm And what does "FF" mean (in the Customer_Addresses table) on this page? -I'm new so it would only let me put in one hyperlink, so copy/paste this to go to the page I'm asking about: databaseanswers.org/tutorial4_db_schema/tutorial_slide_7.htm Thanks. Edit: also, I understand the concepts of primary keys and foreign keys, but what are these other ones used for?

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• Rails ActiveRecord- has_many through and belongs_to a related model

  - by Nick

  I have 3 models sites, user_favorites and users. Relevant relationships: class Site < ActiveRecord::Base has_many :users, :through => :user_favorites class UserFavorite < ActiveRecord::Base belongs_to :user, :counter_cache => true belongs_to :site end class User < ActiveRecord:Base has_many :user_favorites has_many :sites, :through => :user_favorites All of that works just fine. I'd like to add a new attribute to the Site model to indicate which user created it. I don't believe this constitutes a has_and_belongs_to_many scenario. A site has many users through user_favorites but I want it to belong to a single user reflecting the owner/creator. I'm wondering what the ORM best practice is for this. SQL wise I'd just use different joins depending on what I was trying to query with a created_by FK in Site. Sorry if I'm missing something basic here. Thanks

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• What Database to distribute as part of a C# app backend

  - by jez

  I am planning on writing and commercialising a C# app which will store data in an underlying database I use MySQL on my environment for my own development and this is what I would have used to write the application for myself (no need to use FK - MyISAM engine would be fine). I am concerned about how easy it will be to distribute the app together with the database engine. Would using MySQL allow me for easy packaging of the app for a "one-click" install on the client side? (ie I do not want them to have to install MySQL by themselves) and also is it feasible from a licensing point of view? Are there other Database systems which would make the process more straight-forward

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• Handling auto-incrementing IDENTITY SQL Server fields with LINQ to SQL in C#

  - by Maxim Z.

  I'm building an ASP.NET MVC site that uses LINQ to SQL to connect to SQL Server, where I have a table that has an IDENTITY bigint primary key column that represents an ID. In one of my code methods, I need to create an object of that table to get its ID, which I will place into another object based on another table (FK-to-PK relationship). At what point is the IDENTITY column value generated and how can I obtain it from my code? Is the right approach to: Create the object that has the IDENTITY column Do an InsertOnSubmit() and SubmitChanges() to submit the object to the database table Get the value of the ID property of the object

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• Select distinct users with referrals

  - by Mark

  I have a bunch of Users. Since Django doesn't really let me extend the default User model, they each have Profiles. The Profiles have a referred_by field (a FK to User). I'm trying to get a list of Users with = 1 referral. Here's what I've got so far Profile.objects.filter(referred_by__isnull=False).values_list('referred_by', flat=True) Which gives me a list of IDs of the users who have referrals... but I need it to be distinct, and I want the User object, not their ID. Or better yet, it would be nice if it could return the number of referrals a user has. Any ideas?

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• Wrong SQLServer syntax: need help!

  - by user512602

  Hi, this is what I want to achieve: 4 tables are involved: Players with PlayerID as PK, Competitions with CompetID as PK Results with ResultID as PK and CompetID as FK And the 4th table: PlayerResultts with ResultID + PlayerID as PK and CompetID as new column I created. Competitions, results and PlayerResults are already populated and quite large (300000 PlayerResults so far). In order to populate the PlayerResults.CompetID column, I try a Update ... (Select....) request but I'm not aware of the right syntax and it fails. Here is my feeble attempt: update PlayerResults set competid = (select distinct(r.competid) from results r, playerresults p where r.resultID = p.resultid) Error is (of course): "Msg 512, Level 16, State 1, Line 1 Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , , = or when the subquery is used as an expression." Can someone put me in the right direction? TIA

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• NHibernate Criteria Transform Result

  - by isuruceanu

  Hi I have an SecurityGroup entity witch has Memebers and Application properties. Application is a lookup. So securityGroups is in many-to-many relationship with User table and one-to-many with LookupApplciation (FK) Now I want to select all application linked to a specific user. I have follow criteria: public IList<LookupApplication> GetApplicationByUser(User user) { return this.Session.CreateCriteria(typeof(SecurityGroup), "sg") .CreateAlias("Members", "u") .CreateAlias("Application", "al") .Add(Restrictions.Eq("u.Id", user.Id)) .List<LookupApplication>(); } It trows an exception The value "Edi.Advance.Core.Model.Security.SecurityGroup" is not of type "Edi.Advance.Core.Model.Lookups.LookupApplication" and cannot be used in this generic collection. Parameter name: value and it is right. How can I transform the result to IList<LookupApplication>? Thanks

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• Query multiple currencies

  - by TiuTalk

  I need store multiple currencies on my database... Here's the problem: Example Tables: [ Products ] id (INT, PK) name (VARCHAR) price (DECIMAL) currency (INT, FK) [ Currencies ] id (INT, PK) name (VARCHAR) conversion (DECIMAL) # To U$ I'll store the product price with the currency selected by the user... Later I need to search the products using a price interval like "Search products with price from U$ 50 to U$ 100" and I need the system convert these values "on the fly" to run the SQL Query and filter the products. And I really don't know how to make this query... :/

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• Help needed with Linq To Sql Query

  - by fearofawhackplanet

  I have the concept of valid/ordered transitions. So for example, it's not possible to move to status In progress from status Complete. Current and Next in table StatusTransition are FK (StatusType.Id). The Linq generator has created the following relations: Child Property Name: StatusTransitions1 Parent Property Name: StatusType1 Participating Properties: StatusType.Id -> StatusTransition.Next Child Property Name: StatusTransitions Parent Property Name: StatusType Participating Properties: StatusType.Id -> StatusTransition.Current I'm normally ok with Linq but I'm having difficulty getting the list of valid Next StatusTypes from the Current status. public List<StatusType> GetValidStatusTransitions(int statusId) { // trying to write something like the following // (obviously not correct) return _statusRepository .Where(s => s.Id == statusId) .Next.StatusTypes; }

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• How to convert full outer join query to O-R query?

  - by Kugel

  I'm converting relational database into object-relational in Oracle. I have a query that uses full outer join in the old one. Is it possible to write the same query for O-R database without explicitly using full outer join? For normal inner join it simple, I just use dot notation together with ref/deref. I'm interested in this in general so let's say the relational query is: select a.attr, b.attr from a full outer join b on (a.fk = b.pk); I want to know if it's a good idea to do it this way: select a.attr, b.attr from a_obj a full outer join b_obj b on (a.b_ref = ref(b));

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• Store data in file system rather than SQL or Oracle database.

  - by nunu

  Hi All, As I am working on Employee Management system, I have two table (for example) in database as given below. EmployeeMaster (DB table structure) EmployeeID (PK) | EmployeeName | City MonthMaster (DB table structure) Month | Year | EmployeeID (FK) | PrenentDays | BasicSalary Now my question is, I want to store data in file system rather than storing data in SQL or ORACLE. I want my data in file system storage for Insert, Edit and Delete opration with keeping relation with objects too. I am a C# developer, Could anybody have thoughts or idea on it. (To store data in file system with keeping relations between them) Thanks in advance. Any ideas on it?

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• Doctrine 1.2 Column Naming Conventions for Many To Many Relationships

  - by Alan Storm

  I'm working with an existing database schema, and trying to setup two Doctrine models with a Many to Many relationship, as described in this document When creating tables from scratch, I have no trouble getting this working. However, the existing join tables use a different naming convention that what's described in the Doctrine document. Specifically Table 1 -------------------------------------------------- table_1_id ....other columns.... Table 2 -------------------------------------------------- table_2_id ....other columns.... Join Table -------------------------------------------------- fktable1_id fktable_2_id Basically, the previous developers prefaced all forign keys with an fk. From the examples I've seen and some brief experimenting with code, it appears that Doctrine 1.2 requires that the join table use the same column names as the tables it's joining in Is my assumption correct? If so, has the situation changed in Doctrine 2? If the answers to either of the above are true, how do you configure the models so that all the columns "line up"

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• SQL Find duplicate sets

  - by Aheho

  given this Schema: table tblSET SetID int PK SetName nvarchar(100) Table tblSetItem SetID int PK ItemID int PK tblSetItem.SetID is a FK into the tblSet Table. Some data: tblSet SetID SetName 1 Red 2 Blue 3 Maroon 4 Yellow 5 Sky tblSetItem SetID ItemID 1 100 1 101 2 100 2 108 2 109 3 100 3 101 4 101 4 108 4 109 4 110 5 100 5 108 5 109 I'd like a way to identify which sets contain the same items. In the example above Red and Maroon contain the same items (100,101) and Blue and Sky contain the same values (100,108,109) Is there a sql query which would provide this answer?

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• integrity Constraints on a table.

  - by Dinesh

  See this sample schema Passenger(id PK, Name) Plane(id PK, capacity, type); Flight(id PK, planeId FK(Plane), flightDate, StartLocation, destination) CREATE TABLE Reservation(PassengerId, flightId, PRIMARY KEY (passengerId, flightId), FOREIGN KEY (passengerId) REFERENCES Passenger, FOREIGN KEY (flightId) REFERENCES Flight); I need to define an integrity constraint that enforces the restriction that the number of passengers on a plane cannot exceed the plane’s capacity. I have tried and achieved so far is this. CREATE TABLE Reservation( passengerId INTEGER, flightId INTEGER, PRIMARY KEY (passengerId, flightId), FOREIGN KEY (passengerId) REFERENCES Passenger, FOREIGN KEY (flightId) REFERENCES Flight, Constraint check1 check(Not Exists(select * from Flight s, (select count(*) as totalRes from Reservation group by flightId) t where t.totalRes > s.capacity ) ) ); I am not sure i am doing in right way or not. Any suggestions?

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• What is the fastest way to compare 2 rows in SQL?

  - by Swoosh

  I have 2 different databases. Upon changing something in the big one (i don't have access to), i get some rows imported in my databases in a similar HUGE table. I have a job checking for records in this table, and if any, execute a stored procedure, process and delete from table. Performance. (Huge amount of data) I would like to know what is the fastest way to know if something has changed using let's say 2 imported rows with 100 columns each. Don't have FK-s, don't need. Chances are, that even though I have records in my table, nothing has actually changed. Also. Let's say there is actually changed something. Is it possible for example to check only for changes inside datetime columns? Thanks

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• Single SQL Server Result Set from Query

  - by JamesC

  Hi Please advise on how to merge two results in to one using SQL Server 2005. I have the situation where an Account can have up to two Settlement Instructions and this have been modeled like so: The slim-ed down schema: Account --------------------- Id AccountName PrimarySettlementId (nullable) AlternateSettlementId (nullable) SettlementInstruction ---------------------- Id Name The output I want is a single result set with a select statement something along the lines of this which will allow me to construct some java objects in my Spring row mapper: select Account.Id as accountId, Account.AccountName as accountName, s1.Id as primarySettlementId, s1.Name as primarySettlementName, s2.Id as alternateSettlementId, s2.Name as alternateSettlementName I've tried various things but cannot find a way to get the result set merged in to one where the primary and alternate FK's are not null. Finally I have searched the forum, but nothing quite seems to fit with what I need.

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• Navigating by foreign keys in ADO.NET Entity Framework/MySQL

  - by Werg38

  I am using ASP.NET MVC2 on top of a MySQL database in VS2008. I am using the MySQL ADO.NET connector 6.2.3 to provide the connection for the ADO.NET Entity Data Model. This is mostly working ok, however navigating via foreign keys is causing me a real headache! Here is a simplified example.. Car (Table) CarID PK Colour Doors ManufacturerID FK Manufacturer (Table) ManufacturerID PK Name In the edmx file I can see the 1-many relationship shown as a navigation property in the both the Car and Manufacturer tables. I create a Models.CarRepository that allows me to returns a IQueryable. At the View I want to be able to display the Manufacturer.Name for each car. This is not accessible via the object I get returned. What is best way to implement this? Have I encountered a limitation of the Entity Framework/MySQL combination?

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• How to make my view better to save Django

  - by user558251

  Hy guys sorry for this post but i need help with my application, i need optimize my view. I have 5 models, how i can do this? def save(request): # get the request.POST in content if request.POST: content = request.POST dicionario = {} # create a dict to get the values in content for key,value in content.items(): # get my fk Course.objects if key == 'curso' : busca_curso = Curso.objects.get(id=value) dicionario.update({key:busca_curso}) else: dicionario.update({key:value}) #create the new teacher Professor.objects.create(**dicionario) my questions are? 1 - How i can do this function in a generic way? Can I pass a variable in a %s to create and get? like this way ? foo = "Teacher" , bar = "Course" def save(request, bar, foo): if request post: ... if key == 'course' : get_course = (%s.objects.get=id=value) %bar ... (%s.objects.create(**dict)) %foo ??? i tried do this in my view but don't work =/, can somebody help me to make this work ? Thanks

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• Database normalization and duplicate values

  - by bretddog

  Consider a Parent / Child / GrandChild structure in a database table schema, or even a deeper hierarchy. These being in the same aggregate. One table DAYS keeps a single row per day, and has a "Date" field. This is the root table, or maybe a child of the root. No row can ever be deleted in this table. In this case, however complex my table schema looks like, however far away in the hierarchy any other table is, is there any reason why any other table would hold a Date value? Can't it instead just have a FK to the DAYS table. I obviously assume that the creation of these date fields happen not before such datefield exist in the DAYS table. I'm now thinking just about the date part to be relevant, not the time part. Not sure if all databases can store these individually. That's maybe relevant, but not really the focus of the question.

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• Select all rows where there is not a specific value in a different table

  - by JMC Creative

  This is a wordpress installation, but I think the question is more of a general sql question. First off, my sql skills are not great (I don't even know if I'm following the correct format for illustrating the db). I've got two tables: wp_posts : ID (pk) | post_name | ... ---------------------------- 45 | "Hello" 91 | "Funny" 16 | "Wheat" wp_postmeta : post_id (fk) | meta_key | meta_value | ... ------------------------------------------------ 45 | "_edit_lock" | 5789789834 45 | "fizzbizz" | "foobar" 91 | "_something" | "teve" 16 | "_edit_lock" | 8798756 I would to select all rows in wp_posts where there is NO corresponding row in wp_postmeta where meta_key = "fizzbizz" I originally had this query, but someone pointed out that it would not retrive ID = '16' in the above case. How would I correctly write the query? $pageposts = $wpdb->get_results(" SELECT * FROM wp_posts p JOIN wp_postmeta m ON p.ID = m.post_id WHERE m.meta_key <> 'fizzbizz' ORDER BY p.post_date DESC; ");

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• Translate SQL to LINQ query - group/join/filter

  - by Paddy

  I have the following query: SELECT S.[FlowOrder], S.[DESCRIPTION], COUNT(I.ID) FROM WorkFlowStatus AS S INNER JOIN Item AS I ON S.ID = I.StatusID WHERE I.Installation = '1' GROUP BY S.[Description], S.[FlowOrder] ORDER BY S.[FlowOrder] Which gives me the count of an item, grouped by a foreign key to workflow, outputting the descriptive name from my FK table. I've go this far with the LINQ query (using LINQ-to-SQL) in the background: var items = from s in _entities.WorkflowStatus join i in _entities.Items on s.ID equals i.StatusId into Statuses orderby s.FlowOrder select new {s.Description, ItemCount = Statuses.Count() }; How do I get the where clause in the SQL into this LINQ query?

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• How Do I Update a Table From Another Table Only If the Result Count is 1?

  - by Russ Bradberry

  I have a table of 2 tables in a one to many relationship. I want to run an update script that will update the table with the FK of the related table only if there is one result (because if there is multiple then we need to decide which one to use, in another method) Here is what I have so far: UPDATE import_hourly_event_reports i SET i.banner_id = b.banner_id FROM banner b JOIN plan p ON b.plan_id = p.id WHERE b.campain_id = i.campaign_id AND b.size_id = i.size_id AND p.site_id = i.site_id HAVING COUNT(b.banner_id) = 1 As you can see, the HAVING clause doesn't quite work as I'd expect it. I only want to update the row in the import table with the id of the banner from the banner table if the count is equal to 1.

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• SSAS OLAP MDX and relationships

  - by Sonic Soul

  I new to OLAP, and still not sure how to create a relationship between 2 or more entities. I am basing my cube on views. For simplicity sake let's call them like this: viewParent (ParentID PK) viewChild (ChildID PK, ParentID FK) these views have more fields, but they're not important for this question. in my data source, i defined a relationship between viewParent and viewChild using ParentID for the link. As for measures, i was forced to create separate measures for Parent and Child. in my MDX query however, the relationship does not seem to be enforced. If i select record count for parent, child, and add some filters for the parent, the child count is not reflecting it.. SELECT { [Measures].[ParentCount],[Measures].[ChildCount] } ON COLUMNS FROM [Cube] WHERE { ( {[Time].[Month].&[2011-06-01T00:00:00]} ,{[SomeDimension].&[Foo]} ) } the selected ParentCount is correct, but ChildCount is not affected by any of the filters (because they are parent filters). However, since i defined a relationship, how can i take advantage of that to filter children by parent filter?

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• Automatic form generation software

  - by Jonathan

  Hi! I'm using winforms. I spend a lot of time drawing forms (maybe not a lot, but it is a boring task). To sum up... I want to develop a simple aplication that connect to a sql server database, let the user to select a table, and put the controls in a form for me (generate the designer code), based on the tipe of each column. Then my app will name each control like the column of the table, set the maxlengh property (if the type is varchar), and create a label with the same text near the control. If the column is a FK, then the app will draw a combobox and so on. I saw that Telerik Open ORM make something like this, but I only need a simple app for the IU Generation. If the same day I finish my little application I discover a tool that make the same... I will feel myself stupid :D Are there any tool out there that do this work for me? Thanks

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• Error 1005 when adding a foreign key constraint on mysql table

  - by luc

  Hello, I have a problem when upgrading a django and mysql app with south. I've tried to make a sql-based upgrade with the code generated by the django sqlall command and I have a similar problem. Here is the sql code: CREATE TABLE `programmations_basissupport` ( `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY, `value` numeric(6, 0) NOT NULL ) ALTER TABLE `programmations_concert` ADD `basis_support_id` integer AFTER program_status_id; ALTER TABLE `programmations_concert` ADD CONSTRAINT `basis_support_id_refs_id_1e4ed8d7` FOREIGN KEY (`basis_support_id`) REFERENCES `programmations_basissupport` (`id`); An error is raised when adding the FK constraint: ERROR 1005 (HY000): Can't create table 'apidev_mnl.#sql-106e_632b00a' (errno: 150) Does anybody have an idea? Update: DEFAULT values where missing but even if I add the default='' in the django model, the creation of foreign keys fails. Thanks for your help

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