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• MVC 4 Authentication

  - by Aligned

  First: After searching for awhile to figure out what’s new/different with MVC 4 and forms authentication, this is the best article I've found on the subject: http://weblogs.asp.net/jgalloway/archive/2012/08/29/simplemembership-membership-providers-universal-providers-and-the-new-asp-net-4-5-web-forms-and-asp-net-mvc-4-templates.aspx Some quotes from the article: “The ASP.NET Web Pages team designed SimpleMembership to (wait for it) simplify the task of dealing with membership” "WSAT is built to work with ASP.NET Membership, and is not compatible with Simple Membership. There are two main options there: Use the WebSecurity and OAuthWebSecurity API to manage the users and roles Create a web admin using the above APIs Since SimpleMembership runs on top of your database, you can update your users as you would any other data - via EF or even in direct database edits (in development, of course)" “If you want to use an existing ASP.NET Membership Provider in ASP.NET MVC 4, you can't use the new AccountController. You can do a few things:” “Universal Providers do not work with Simple Membership.” ~ this post (look for Bob.at.SBS’s answer) says Universal Providers is not needed for MVC 4 to work in Azure)   I've been trying to figure out the Forms Authentication in MVC4. It's different than the past approach (aspnet_regsql). If you do file new project -> MVC 4 -> internet application, you get a really nice template with the controller and model setup for you. However, the tables are different than using aspnet_regsql and the ASP.Net Configuration tool (WSAT) wasn’t connecting to the data I had (it was creating an App_Data/aspnet.mdf file, which I didn’t see right away). Points of Note The database tables are created in the SimpleMembershipInitializer class, when you first run your app using Entity Framework 5 migration functionality. The tables created are webpages_Membership, webpages_OAuthMembership, webpages_Roles, webpages_UsersInRoles, UserProfile. Web.config settings don’t seem to be needed.   Scott Hanselman on Universal Providers was also useful if not somewhat out dated. Universal Providers and SimpleMembership are not compatible. http://www.asp.net/web-pages/tutorials/security/16-adding-security-and-membership – walk-through

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• What Every Developer Should Know About MSI Components

  - by Alois Kraus

  Hopefully nothing. But if you have to do more than simple XCopy deployment and you need to support updates, upgrades and perhaps side by side scenarios there is no way around MSI. You can create Msi files with a Visual Studio Setup project which is severely limited or you can use the Windows Installer Toolset. I cannot talk about WIX with my German colleagues because WIX has a very special meaning. It is funny to always use the long name when I talk about deployment possibilities. Alternatively you can buy commercial tools which help you to author Msi files but I am not sure how good they are. Given enough pain with existing solutions you can also learn the MSI Apis and create your own packaging solution. If I were you I would use either a commercial visual tool when you do easy deployments or use the free Windows Installer Toolset. Once you know the WIX schema you can create well formed wix xml files easily with any editor. Then you can “compile” from the wxs files your Msi package. Recently I had the “pleasure” to get my hands dirty with C++ (again) and the MSI technology. Installation is a complex topic but after several month of digging into arcane MSI issues I can safely say that there should exist an easier way to install and update files as today. I am not alone with this statement as John Robbins (creator of the cool tool Paraffin) states: “.. It's a brittle and scary API in Windows …”. To help other people struggling with installation issues I present you the advice I (and others) found useful and what will happen if you ignore this advice. What is a MSI file? A MSI file is basically a database with tables which reference each other to control how your un/installation should work. The basic idea is that you declare via these tables what you want to install and MSI controls the how to get your stuff onto or off your machine. Your “stuff” consists usually of files, registry keys, shortcuts and environment variables. Therefore the most important tables are File, Registry, Environment and Shortcut table which define what will be un/installed. The key to master MSI is that every resource (file, registry key ,…) is associated with a MSI component. The actual payload consists of compressed files in the CAB format which can either be embedded into the MSI file or reside beside the MSI file or in a subdirectory below it. To examine MSI files you need Orca a free MSI editor provided by MS. There is also another free editor called Super Orca which does support diffs between MSI and it does not lock the MSI files. But since Orca comes with a shell extension I tend to use only Orca because it is so easy to right click on a MSI file and open it with this tool. How Do I Install It? Double click it. This does work for fresh installations as well as major upgrades. Updates need to be installed via the command line via msiexec /i <msi> REINSTALL=ALL REINSTALLMODE=vomus   This tells the installer to reinstall all already installed features (new features will NOT be installed). The reinstallmode letters do force an overwrite of the old cached package in the %WINDIR%\Installer folder. All files, shortcuts and registry keys are redeployed if they are missing or need to be replaced with a newer version. When things did go really wrong and you want to overwrite everything unconditionally use REINSTALLMODE=vamus. How To Enable MSI Logs? You can download a MSI from Microsoft which installs some registry keys to enable full MSI logging. The log files can be found in your %TEMP% folder and are called MSIxxxx.log. Alternatively you can add to your msiexec command line the option msiexec …. /l*vx <LogFileName> Personally I find it rather strange that * does not mean full logging. To really get all logs I need to add v and x which is documented in the msiexec help but I still find this behavior unintuitive. What are MSI components? The whole MSI logic is bound to the concept of MSI components. Nearly every msi table has a Component column which binds an installable resource to a component. Below are the screenshots of the FeatureComponents and Component table of an example MSI. The Feature table defines basically the feature hierarchy.  To find out what belongs to a feature you need to look at the FeatureComponents table where for each feature the components are listed which will be installed when a feature is installed. The MSI components are defined in the  Component table. This table has as first column the component name and as second column the component id which is a GUID. All resources you want to install belong to a MSI component. Therefore nearly all MSI tables have a Component_ column which contains the component name. If you look e.g. a the File table you see that every file belongs to a component which is true for all other tables which install resources. The component table is the glue between all other tables which contain the resources you want to install. So far so easy. Why is MSI then so complex? Most MSI problems arise from the fact that you did violate a MSI component rule in one or the other way. When you install a feature the reference count for all components belonging to this feature will increase by one. If your component is installed by more than one feature it will get a higher refcount. When you uninstall a feature its refcount will drop by one. Interesting things happen if the component reference count reaches zero: Then all associated resources will be deleted. That looks like a reasonable thing and it is. What it makes complex are the strange component rules you have to follow. Below are some important component rules from the Tao of the Windows Installer … Rule 16: Follow Component Rules Components are a very important part of the Installer technology. They are the means whereby the Installer manages the resources that make up your application. The SDK provides the following guidelines for creating components in your package: Never create two components that install a resource under the same name and target location. If a resource must be duplicated in multiple components, change its name or target location in each component. This rule should be applied across applications, products, product versions, and companies. Two components must not have the same key path file. This is a consequence of the previous rule. The key path value points to a particular file or folder belonging to the component that the installer uses to detect the component. If two components had the same key path file, the installer would be unable to distinguish which component is installed. Two components however may share a key path folder. Do not create a version of a component that is incompatible with all previous versions of the component. This rule should be applied across applications, products, product versions, and companies. Do not create components containing resources that will need to be installed into more than one directory on the user’s system. The installer installs all of the resources in a component into the same directory. It is not possible to install some resources into subdirectories. Do not include more than one COM server per component. If a component contains a COM server, this must be the key path for the component. Do not specify more than one file per component as a target for the Start menu or a Desktop shortcut. … And these rules do not even talk about component ids, update packages and upgrades which you need to understand as well. Lets suppose you install two MSIs (MSI1 and MSI2) which have the same ComponentId but different component names. Both do install the same file. What will happen when you uninstall MSI2?   Hm the file should stay there. But the component names are different. Yes and yes. But MSI uses not use the component name as key for the refcount. Instead the ComponentId column of the Component table which contains a GUID is used as identifier under which the refcount is stored. The components Comp1 and Comp2 are identical from the MSI perspective. After the installation of both MSIs the Component with the Id {100000….} has a refcount of two. After uninstallation of one MSI there is still a refcount of one which drops to zero just as expected when we uninstall the last msi. Then the file which was the same for both MSIs is deleted. You should remember that MSI keeps a refcount across MSIs for components with the same component id. MSI does manage components not the resources you did install. The resources associated with a component are then and only then deleted when the refcount of the component reaches zero.   The dependencies between features, components and resources can be described as relations. m,k are numbers >= 1, n can be 0. Inside a MSI the following relations are valid Feature    1  –> n Components Component    1 –> m Features Component      1  –>  k Resources These relations express that one feature can install several components and features can share components between them. Every (meaningful) component will install at least one resource which means that its name (primary key to stay in database speak) does occur in some other table in the Component column as value which installs some resource. Lets make it clear with an example. We want to install with the feature MainFeature some files a registry key and a shortcut. We can then create components Comp1..3 which are referenced by the resources defined in the corresponding tables.   Feature Component Registry File Shortcuts MainFeature Comp1 RegistryKey1     MainFeature Comp2   File.txt   MainFeature Comp3   File2.txt Shortcut to File2.txt   It is illegal that the same resource is part of more than one component since this would break the refcount mechanism. Lets illustrate this:            Feature ComponentId Resource Reference Count Feature1 {1000-…} File1.txt 1 Feature2 {2000-….} File1.txt 1 The installation part works well but what happens when you uninstall Feature2? Component {20000…} gets a refcount of zero where MSI deletes all resources belonging to this component. In this case File1.txt will be deleted. But Feature1 still has another component {10000…} with a refcount of one which means that the file was deleted too early. You just have ruined your installation. To fix it you then need to click on the Repair button under Add/Remove Programs to let MSI reinstall any missing registry keys, files or shortcuts. The vigilant reader might has noticed that there is more in the Component table. Beside its name and GUID it has also an installation directory, attributes and a KeyPath. The KeyPath is a reference to a file or registry key which is used to detect if the component is already installed. This becomes important when you repair or uninstall a component. To find out if the component is already installed MSI checks if the registry key or file referenced by the KeyPath property does exist. When it does not exist it assumes that it was either already uninstalled (can lead to problems during uninstall) or that it is already installed and all is fine. Why is this detail so important? Lets put all files into one component. The KeyPath should be then one of the files of your component to check if it was installed or not. When your installation becomes corrupt because a file was deleted you cannot repair it with the Repair button under Add/Remove Programs because MSI checks the component integrity via the Resource referenced by its KeyPath. As long as you did not delete the KeyPath file MSI thinks all resources with your component are installed and never executes any repair action. You get even more trouble when you try to remove files during an upgrade (you cannot remove files during an update) from your super component which contains all files. The only way out and therefore best practice is to assign for every resource you want to install an extra component. This ensures painless updatability and repairs and you have much less effort to remove specific files during an upgrade. In effect you get this best practice relation Feature 1  –> n Components Component   1  –>  1 Resources MSI Component Rules Rule 1 – One component per resource Every resource you want to install (file, registry key, value, environment value, shortcut, directory, …) must get its own component which does never change between versions as long as the install location is the same. Penalty If you add more than one resources to a component you will break the repair capability of MSI because the KeyPath is used to check if the component needs repair. MSI ComponentId Files MSI 1.0 {1000} File1-5 MSI 2.0 {2000} File2-5 You want to remove File1 in version 2.0 of your MSI. Since you want to keep the other files you create a new component and add them there. MSI will delete all files if the component refcount of {1000} drops to zero. The files you want to keep are added to the new component {2000}. Ok that does work if your upgrade does uninstall the old MSI first. This will cause the refcount of all previously installed components to reach zero which means that all files present in version 1.0 are deleted. But there is a faster way to perform your upgrade by first installing your new MSI and then remove the old one.  If you choose this upgrade path then you will loose File1-5 after your upgrade and not only File1 as intended by your new component design.   Rule 2 – Only add, never remove resources from a component If you did follow rule 1 you will not need Rule 2. You can add in a patch more resources to one component. That is ok. But you can never remove anything from it. There are tricky ways around that but I do not want to encourage bad component design. Penalty Lets assume you have 2 MSI files which install under the same component one file   MSI1 MSI2 {1000} - ComponentId {1000} – ComponentId File1.txt File2.txt   When you install and uninstall both MSIs you will end up with an installation where either File1 or File2 will be left. Why? It seems that MSI does not store the resources associated with each component in its internal database. Instead Windows will simply query the MSI that is currently uninstalled for all resources belonging to this component. Since it will find only one file and not two it will only uninstall one file. That is the main reason why you never can remove resources from a component!   Rule 3 Never Remove A Component From an Update MSI. This is the same as if you change the GUID of a component by accident for your new update package. The resulting update package will not contain all components from the previously installed package. Penalty When you remove a component from a feature MSI will set the feature state during update to Advertised and log a warning message into its log file when you did enable MSI logging. SELMGR: ComponentId '{2DCEA1BA-3E27-E222-484C-D0D66AEA4F62}' is registered to feature 'xxxxxxx, but is not present in the Component table.  Removal of components from a feature is not supported! MSI (c) (24:44) [07:53:13:436]: SELMGR: Removal of a component from a feature is not supported Advertised means that MSI treats all components of this feature as not installed. As a consequence during uninstall nothing will be removed since it is not installed! This is not only bad because uninstall does no longer work but this feature will also not get the required patches. All other features which have followed component versioning rules for update packages will be updated but the one faulty feature will not. This results in very hard to find bugs why an update was only partially successful. Things got better with Windows Installer 4.5 but you cannot rely on that nobody will use an older installer. It is a good idea to add to your update msiexec call MSIENFORCEUPGRADECOMPONENTRULES=1 which will abort the installation if you did violate this rule.

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• Any simple approaches for managing customer data change requests for global reference files?

  - by Kelly Duke

  For the first time, I am developing in an environment in which there is a central repository for a number of different industry standard reference data tables and many different customers who need to select records from these industry standard reference data tables to fill in foreign key information for their customer specific records. Because these industry standard reference files are utilized by all customers, I want to reserve Create/Update/Delete access to these records for global product administrators. However, I would like to implement a (semi-)automated interface by which specific customers could request record additions, deletions or modifications to any of the industry standard reference files that are shared among all customers. I know I need something like a "data change request" table specifying: user id, user request datetime, request type (insert, modify, delete), a user entered text explanation of the change request, the user request's current status (pending, declined, completed), admin resolution datetime, admin id, an admin entered text description of the resolution, etc. What I can't figure out is how to elegantly handle the fact that these data change requests could apply to dozens of different tables with differing table column definitions. I would like to give the customer users making these data change requests a convenient way to enter their proposed record additions/modifications directly into CRUD screens that look very much like the reference table CRUD screens they don't have write/delete permissions for (with an additional text explanation and perhaps request priority field). I would also like to give the global admins a tool that allows them to view all the outstanding data change requests for the users they oversee sorted by date requested or user/date requested. Upon selecting a data change request record off the list, the admin would be directed to another CRUD screen that would be populated with the fields the customer users requested for the new/modified industry standard reference table record along with customer's text explanation, the request status and the text resolution explanation field. At this point the admin could accept/edit/reject the requested change and if accepted the affected industry standard reference file would be automatically updated with the appropriate fields and the data change request record's status, text resolution explanation and resolution datetime would all also be appropriately updated. However, I want to keep the actual production reference tables as simple as possible and free from these extraneous and typically null customer change request fields. I'd also like the data change request file to aggregate all data change requests across all the reference tables yet somehow "point to" the specific reference table and primary key in question for modification & deletion requests or the specific reference table and associated customer user entered field values in question for record creation requests. Does anybody have any ideas of how to design something like this effectively? Is there a cleaner, simpler way I am missing? Thank you so much for reading.

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• How to create Query syntax for multiple DataTable for implementing IN operator of Sql Server

  - by Shantanu Gupta

  I have fetched 3-4 tables by executing my stored procedure. Now they resides on my dataset. I have to maintain this dataset for multiple forms and I am not doing any DML operation on this dataset. Now this dataset contains 4 tables out of which i have to fetch some records to display data. Data stored in tables are in form of one to many relationship. i.e. In case of transactions. N records per record. Then these N records are further mapped to M records of 3rd table. Table 1 MAP_ID GUEST_ID DEPARTMENT_ID PARENT_ID PREFERENCE_ID -------------------- -------------------- -------------------- -------------------- -------------------- 19 61 1 1 5 14 61 1 5 15 15 61 2 4 10 18 61 2 13 23 17 61 2 20 26 16 61 40 40 41 20 62 1 5 14 21 62 1 5 15 22 62 1 6 16 24 62 2 3 4 23 62 2 4 9 27 62 2 13 23 25 62 2 20 24 26 62 2 20 25 28 63 1 1 5 29 63 1 1 8 34 63 1 5 15 30 63 2 4 10 33 63 2 4 11 31 63 2 13 23 32 63 40 40 41 35 65 1 NULL 1 36 65 1 NULL 1 38 68 2 13 22 37 68 2 20 25 39 68 2 23 27 40 92 1 NULL 1 Table 2 Department_ID Department_Name Parent_Id Parent_Name -------------------- ----------------------- --------------- ---------------------------------------------------------------------------------- 1 Food 1, 5, 6 Food, North Indian, South Indian 2 Lodging 3, 4, 13, 20, 23 Room, Floor, Non Air Conditioned, With Balcony, Without Balcony 40 New 40 SubNew TABLE 3 Parent_Id Parent_Name Preference_ID Preference_Name -------------------- ----------------------------------------------- ----------------------- ------------------- NULL NULL NULL NULL 1 Food 5, 8 North Indian, Italian 3 Room 4 Floor 4 Floor 9, 10, 11 First, Second, Third 5 North Indian 14, 15 X, Y 6 South Indian 16 Dosa 13 Non Air Conditioned 22, 23 With Balcony, Without Balcony 20 With Balcony 24, 25, 26 Mountain View, Ocean View, Garden View 23 Without Balcony 27 Mountain View 40 New 41 SubNew I have these 3 tables that are related in some fashion like this. Table 1 will be the master for these 2 tables i.e. table 2 and table 3. I need to query on them as SELECT Department_Id, Department_Name, Parent_Name FROM Table2 WHERE Department_Id in ( SELECT Department_Id FROM Table1 WHERE guest_id=65 ) SELECT Parent_Id, Parent_Name, Preference_Name FROM Table3 WHERE PARENT_ID in ( SELECT parent_id FROM Table1 WHERE guest_id=65 ) Now I need to use these queries on DataTables. So I am using Query Syntax for this and reached up to this point. var dept_list= from dept in DtMapGuestDepartment.AsEnumerable() where dept.Field<long>("PK_GUEST_ID")==long.Parse(63) select dept; This should give me the list of all departments that has guest id =63 Now I want to select all departments_name and parent_name from Table 2 where guest_id=63 i.e. departments that i fetched above. This same case will be followed for Table3. Please suggest how to do this. Thanks for keeping up patience for reading my question.

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• Rails / ActiveRecord Modeling Help

  - by JM

  I’m trying to model a relationship in ActiveRecord and I think it’s a little beyond my skill level. Here’s the background. This is a horse racing project and I’m trying to model a horses Connections over time. Connections are defined as the Horse’s Current: Owner, Trainer and Jockey. Over time, a horse’s connections can change for a lot of different reasons: The owner sells the horse in a private sale The horse is claimed (purchase in a public sale) The Trainer switches jockeys The owner switches trainers In my first attempt at modeling this, I created the following tables: Horses, Owners, Trainers, Jockeys and Connections. Essentially, the Connections table was the has-many-through join table and was structured as follows: Connections Table 1 Id Horse_id Owner_id Trainer_id Jockey_id Status_Code Status_Date Change_Code The Horse, Owner, Trainer and Jockey foreign keys are self explanatory. The status code is 1 or 0 (1 active, 0 inactive) and the status date is the date the status changed. Change_code is and integer or string value that represent the reason for the change (private sale, claim, jockey change, etc) The key benefit of this approach is that the Connection is represented as one record in the connections table. The downside is that I have to have a table for Owner (1), Trainer (2) and Jockey (3) when one table could due. In my second attempt at modeling this I created the following tables: Horses, Connections, Entities The Entities tables has the following structure Entities Table id First_name Last_name Role where Role represents if the entity is a Owner, Trainer or Jockey. Under this approach, my Connections table has the following structure Connections Table 2 id Horse_id Entity_id Role Status_Code Status_Date Change_Code 1 1 1 1 1 1/1/2010 2 1 4 2 1 1/1/2010 3 1 10 3 1 1/1/2010 This approach has the benefit of eliminating two tables, but on the other hand the Connection is now comprised of three different records as opposed to one in the first approach. What believe I’m looking for is an approach that allows me to capture the Connection in one record, but also uses an Entities table with roles instead of the Owner, Trainer and Jockey tables. I’m new to ActiveRecord and rails so any and all input would be greatly appreciated. Perhaps there are other ways that would even be better. Thanks!

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• ASP.NET Repeater and DataBinder.Eval

  - by Fernando

  I've got a <asp:Repeater> in my webpage, which is bound to a programatically created dataset. The purpose of this repeater is to create an index from A-Z, which, when clicked, refreshes the information on the page. The repeater has a link button like so: <asp:LinkButton ID="indexLetter" Text='<%#DataBinder.Eval(Container.DataItem,"letter")%>' runat="server" CssClass='<%#DataBinder.Eval(Container.DataItem, "cssclass")%>' Enabled='<%#DataBinder.Eval(Container.DataItem,"enabled")%>'></asp:LinkButton> The dataset is created the following way: protected DataSet getIndex(String index) { DataSet ds = new DataSet(); ds.Tables.Add("index"); ds.Tables["index"].Columns.Add("letter"); ds.Tables["index"].Columns.Add("cssclass"); ds.Tables["index"].Columns.Add("enabled"); char alphaStart = Char.Parse("A"); char alphaEnd = Char.Parse("Z"); for (char i = alphaStart; i <= alphaEnd; i++) { String cssclass="", enabled="true"; if (index == i.ToString()) { cssclass = "selected"; enabled = "false"; } ds.Tables["index"].Rows.Add(new Object[3] {i.ToString(),cssclass,enabled }); } return ds; } However, when I run the page, a "Specified cast is not valid exception" is thrown in Text='<%#DataBinder.Eval(Container.DataItem,"letter")'. I have no idea why, I have tried manually casting to String with (String), I've tried a ToString() method, I've tried everything. Also, if in the debugger I add a watch for DataBinder.Eval(Container.DataItem,"letter"), the value it returns is "A", which according to me, should be fine for the Text Property. EDIT: Here is the exception: System.InvalidCastException was unhandled by user code Message="Specified cast is not valid." Source="App_Web_cmu9mtyc" StackTrace: at ASP.savecondition_aspx._DataBinding_control7(Object sender, EventArgs e) in e:\Documents and Settings\Fernando\My Documents\Visual Studio 2008\Projects\mediTrack\mediTrack\saveCondition.aspx:line 45 at System.Web.UI.Control.OnDataBinding(EventArgs e) at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBind() at System.Web.UI.Control.DataBindChildren() InnerException: Any advice will be greatly appreciated, thank you EDIT 2: Fixed! The problem was not in the Text or CSS tags, but in the Enabled tag, I had to cast it to a Boolean value. The problem was that the exception was signaled at the Text tag, I don't know why

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• Entity Framework - Single EMDX Mapping Multiple Database

  - by michaelalisonalviar

  Because of my recent craze on Entity Framework thanks to Sir Humprey, I have continuously searched the Internet for tutorials on how to apply it to our current system. So I've come to learn that with EF, I can eliminate the numerous coding of methods/functions for CRUD operations, my overly used assigning of connection strings, Data Adapters or Data Readers as Entity Framework will map my desired database and will do its magic to create entities for each table I want (using EF Powertool) and does all the methods/functions for my Crud Operations. But as I begin applying it to a new project I was assigned to, I realized our current server is designed to contain each similar entities in different databases. For example Our lookup tables are stored in LookupDb, Accounting-related tables are in AccountingDb, Sales-related tables in SalesDb. My dilemma is I have to use an existing table from LookupDB and use it as a look-up for my new table. Then I have found Miss Rachel's Blog (here)Thank You Miss Rachel!  which enables me to let EF think that my TableLookup1 is in the AccountingDB using the following steps. Im on VS 2010, I am using C# , Using Entity Framework 5, SQL Server 2008 as our DB ServerStep 1:Creating A SQL Synonym. If you want a more detailed discussion on synonyms, this was what i have read -> (link here). To simply put it, A synonym enabled me to simplify my query for the Look-up table when I'm using the AccountingDB fromSELECT [columns] FROM LookupDB.dbo.TableLookup1toSELECT [columns] FROM TableLookup1Syntax: CREATE SYNONYM  TableLookup1(1) FOR LookupDB.dbo.TableLookup1 (2)1. What you want to call the table on your other DB2. DataBaseName.schema.TableNameStep 2: We will now follow Miss Rachel's steps. you can either visit the link on the original topic I posted earlier or just follow the step I made.1. I created a Visual Basic Solution that will contain the 4 projects needed to complete the merging2. First project will contain the edmx file pointing to the AccountingDB3. Second project will contain the edmx file pointing to the LookupDB4. Third Project will will be our repository of the merged edmx file. Create an edmx file pointing To AccountingDB as this the database that we created the Synonym on.Reminder: Aside from using the same name for the Entities, please make sure that you have the same Model Namespace for all your Entities  5. Fourth project that will contain the beautiful EDMX merger that Miss Rachel created that will free you from Hard coding of the merge/recoding the Edmx File of the third project everytime a change is done on either one of the first two projects' Edmx File.6. Run the solution, but make sure that on the solutions properties Single startup project is selected and the project containing the EDMX merger is selected.7. After running the solution, double click on the EDMX file of the 3rd project and set Lazy Loading Enabled = False. This will let you use the tables/entities that you see in that EDMX File.8. Feel free to do your CRUD Operations.I don't know if EF 5 already has a feature to support synonyms as I am still a newbie on that aspect but I have seen a linked where there are supposed suggestions on Entity Framework upgrades and one is the "Support for multiple databases"  So that's it! Thanks for reading!

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• The five steps of business intelligence adoption: where are you?

  - by Red Gate Software BI Tools Team

  When I was in Orlando and New York last month, I spoke to a lot of business intelligence users. What they told me suggested a path of BI adoption. The user’s place on the path depends on the size and sophistication of their organisation. Step 1: A company with a database of customer transactions will often want to examine particular data, like revenue and unit sales over the last period for each product and territory. To do this, they probably use simple SQL queries or stored procedures to produce data on demand. Step 2: The results from step one are saved in an Excel document, so business users can analyse them with filters or pivot tables. Alternatively, SQL Server Reporting Services (SSRS) might be used to generate a report of the SQL query for display on an intranet page. Step 3: If these queries are run frequently, or business users want to explore data from multiple sources more freely, it may become necessary to create a new database structured for analysis rather than CRUD (create, retrieve, update, and delete). For example, data from more than one system — plus external information — may be incorporated into a data warehouse. This can become ‘one source of truth’ for the business’s operational activities. The warehouse will probably have a simple ‘star’ schema, with fact tables representing the measures to be analysed (e.g. unit sales, revenue) and dimension tables defining how this data is aggregated (e.g. by time, region or product). Reports can be generated from the warehouse with Excel, SSRS or other tools. Step 4: Not too long ago, Microsoft introduced an Excel plug-in, PowerPivot, which allows users to bring larger volumes of data into Excel documents and create links between multiple tables.  These BISM Tabular documents can be created by the database owners or other expert Excel users and viewed by anyone with Excel PowerPivot. Sometimes, business users may use PowerPivot to create reports directly from the primary database, bypassing the need for a data warehouse. This can introduce problems when there are misunderstandings of the database structure or no single ‘source of truth’ for key data. Step 5: Steps three or four are often enough to satisfy business intelligence needs, especially if users are sophisticated enough to work with the warehouse in Excel or SSRS. However, sometimes the relationships between data are too complex or the queries which aggregate across periods, regions etc are too slow. In these cases, it can be necessary to formalise how the data is analysed and pre-build some of the aggregations. To do this, a business intelligence professional will typically use SQL Server Analysis Services (SSAS) to create a multidimensional model — or “cube” — that more simply represents key measures and aggregates them across specified dimensions. Step five is where our tool, SSAS Compare, becomes useful, as it helps review and deploy changes from development to production. For us at Red Gate, the primary value of SSAS Compare is to establish a dialog with BI users, so we can develop a portfolio of products that support creation and deployment across a range of report and model types. For example, PowerPivot and the new BISM Tabular model create a potential customer base for tools that extend beyond BI professionals. We’re interested in learning where people are in this story, so we’ve created a six-question survey to find out. Whether you’re at step one or step five, we’d love to know how you use BI so we can decide how to build tools that solve your problems. So if you have a sixty seconds to spare, tell us on the survey!

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• datagrid filter in c# using sql server

  - by malou17

  How to filter data in datagrid for example if u select the combo box in student number then input 1001 in the text field...all records in 1001 will appear in datagrid.....we are using sql server private void button2_Click(object sender, EventArgs e) { if (cbofilter.SelectedIndex == 0) { string sql; SqlConnection conn = new SqlConnection(); conn.ConnectionString = "Server= " + Environment.MachineName.ToString() + @"\; Initial Catalog=TEST;Integrated Security = true"; SqlDataAdapter da = new SqlDataAdapter(); DataSet ds1 = new DataSet(); ds1 = DBConn.getStudentDetails("sp_RetrieveSTUDNO"); sql = "Select * from Test where STUDNO like '" + txtvalue.Text + "'"; SqlCommand cmd = new SqlCommand(sql, conn); cmd.CommandType = CommandType.Text; da.SelectCommand = cmd; da.Fill(ds1); dbgStudentDetails.DataSource = ds1; dbgStudentDetails.DataMember = ds1.Tables[0].TableName; dbgStudentDetails.Refresh(); } else if (cbofilter.SelectedIndex == 1) { //string sql; //SqlConnection conn = new SqlConnection(); //conn.ConnectionString = "Server= " + Environment.MachineName.ToString() + @"\; Initial Catalog=TEST;Integrated Security = true"; //SqlDataAdapter da = new SqlDataAdapter(); //DataSet ds1 = new DataSet(); //ds1 = DBConn.getStudentDetails("sp_RetrieveSTUDNO"); //sql = "Select * from Test where Name like '" + txtvalue.Text + "'"; //SqlCommand cmd = new SqlCommand(sql,conn); //cmd.CommandType = CommandType.Text; //da.SelectCommand = cmd; //da.Fill(ds1); // dbgStudentDetails.DataSource = ds1; //dbgStudentDetails.DataMember = ds1.Tables[0].TableName; //ds.Tables[0].DefaultView.RowFilter = "Studno = + txtvalue.text + "; dbgStudentDetails.DataSource = ds.Tables[0]; dbgStudentDetails.Refresh(); } }

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• [Linq to SQL] Multiple foreign keys to the same table

  - by cdonner

  I have a reference table with all sorts of controlled value lookup data for gender, address type, contact type, etc. Many tables have multiple foreign keys to this reference table I also have many-to-many association tables that have two foreign keys to the same table. Unfortunately, when these tables are pulled into a Linq model and the DBML is generated, SQLMetal does not look at the names of the foreign key columns, or the names of the constraints, but only at the target table. So I end up with members called Reference1, Reference2, ... not very maintenance-friendly. Example: <Association Name="tb_reference_tb_account" Member="tb_reference" <====== ThisKey="shipping_preference_type_id" OtherKey="id" Type="tb_reference" IsForeignKey="true" /> <Association Name="tb_reference_tb_account1" Member="tb_reference1" <====== ThisKey="status_type_id" OtherKey="id" Type="tb_reference" IsForeignKey="true" /> I can go into the DBML and manually change the member names, of course, but this would mean I can no longer round-trip my database schema. This is not an option at the current stage of the model, which is still evolving. Splitting the reference table into n individual tables is also not desirable. I can probably write a script that runs against the XML after each generation and replaces the member name with something derived from ThisKey (since I adhere to a naming convention for these types of keys). Has anybody found a better solution to this problem?

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• Schema objects not visible in SQL Server Management Studio 2008

  - by Germ

  I'm experiencing a weird problem with a SQL login. When I connect to the server in Microsoft SQL Server Management Studio (2008) using this account, I cannot see any of the tables, stored procedures etc. that this account should have access to on a particular database. When I connect to the same server within Visual Studio (2008) with the same account everything is there. When I connect with the same account on a Virtual Machine everything is there. I've also had a co-worker connect to the server using the same login and he's able to view everything as well. I use Microsoft SQL Server Management Studio all day connecting to different servers and databases and I've never experienced this problem. Does anyone have any suggestions on how I can diagnose this problem? I've checked to make sure I don't have any Table filters etc. There's several database on this server and I'm able to see the correct tables that this account has access to in the other databases just fine. Running this query lists the tables I'm expecting to see. SELECT * FROM INFORMATION_SCHEMA.TABLES

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• Rails Fixtures Don't Seem to Support Transitive Associations

  - by Rick Wayne

  So I've got 3 models in my app, connected by HABTM relations: class Member < ActiveRecord::Base has_and_belongs_to_many :groups end class Group < ActiveRecord::Base has_and_belongs_to_many :software_instances end class SoftwareInstance < ActiveRecord::Base end And I have the appropriate join tables, and use foxy fixtures to load them: -- members.yml -- rick: name: Rick groups: cals -- groups.yml -- cals: name: CALS software_instances: delphi -- software_instances.yml -- delphi: name: No, this is not a joke, someone in our group is still maintaining Delphi apps... And I do a rake db:fixtures:load, and examine the tables. Yep, the join tables groups_members and groups_software_instances have appropriate IDs in, big numbers generated by hashing the fixture names. Yay! And if I run script/console, I can look at rick's groups and see that cals is in there, or cals's software_instances and delphi shows up. (Likewise delphi knows that it's in the group cals.) Yay! But if I look at rick.groups[0].software_instances...nada. []. And, oddly enough, rick.groups[0].id is something like 30 or 10, not 398398439. I've tried swapping around where the association is defined in the fixtures, e.g. -- members.yml -- rick name: rick -- groups.yml -- cals name: CALS members: rick No error, but same result. (Later: Confirmed, same behavior on MySQL. In fact I get the same thing if I take the foxification out and use ERB to directly create the join tables, so: -- license_groups_software_instances -- cals_delphi: group_id: <%= Fixtures.identify 'cals' % software_instance_id: <%= Fixtures.identify 'delphi' $ Before I chuck it all, reject foxy fixtures and all who sail in her and just hand-code IDs...anybody got a suggestion as to why this is happening? I'm currently working in Rails 2.3.2 with sqlite3, this occurs on both OS X and Ubuntu (and I think with MySQL too). TIA, my compadres.

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• OleDb database to DataSet and back in c#?

  - by Troy

  I'm writing a program that lets a user: Connect to an (arbitrary) View all of the tables in that database in separate DataGridViews Edit them in the program, generate random data, and see the results Choose to commit those changes or revert So I discovered the DataSet class, which looks like it's capable of holding everything that a database would, and I decided that the best thing to do here would be to load everything into one dataset, let the user edit it, and then save the dataset back to the database. The problem is that the only way I can find to load the database tables is this: set = new DataSet(); DataTable schema = connection.GetOleDbSchemaTable( OleDbSchemaGuid.Tables, new string[] { null, null, null, "TABLE" }); foreach (DataRow row in schema.Rows) { string tableName = row.Field<string>("TABLE_NAME"); DataTable dTable = new DataTable(); new OleDbDataAdapter("SELECT * FROM " + tableName, connection).Fill(dTable); dTable.TableName = tableName; set.Tables.Add(dTable); } while it seems like there should be a simpler way given that datasets appear to be designed for exactly this purpose. The real problem though is when I try saving these things. In order to use the OleDbDataAdapter.Update() method, I'm told that I have to provide valid INSERT queries. Doesn't that kind of negate the whole point of having a class to handle this stuff for me? Anyway, I'm hoping somebody can either explain how to load and save a database into a dataset or maybe give me a better idea of how to do what I'm trying to do. I could always parse the commands together myself, but that doesn't seem like the best solution.

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• PostgreSQL: Auto-partition a table

  - by Adam Matan

  Hi, I have a huge database which holds pairs of numbers (A,B), each ranging from 0 to 10,000 and stored as floats. e.g., (1, 9984.4), (2143.44, 124.243), (0.55, 0), ... Since the PostgreSQL table which stores these pairs grew quite large, I have decided to partition it into inheriting sub-tables. I intend to create 100 such tables, each storing a range of 1000x1000. The problem is that these numbers tend to come in large chunks of nearby numbers. It means that in the future, some tables will be nearly empty and some will hold a very large portion of the database. Unfortunately, the distribution of future pairs is yet unknown. I am looking for a way to automatically repartition my table. That means that if a certain subtable holds more than a specific number of pairs, it will be automatically partitioned into four sub-sub tables, and so on. My questions are: Is recursive partitioning and inheritance possible in PostgreSQL 8.3? Will indexes and query plans understand it? What's the best way to split a subtable once it grew too large? I should point out that this isn't a live database, so a downtime of few hours every week is totally acceptable. Thanks in advance, Adam

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• Product Catalog Schema design

  - by FlySwat

  I'm building a proof of concept schema for a product catalog to possibly replace a very aging and crufty one we use. In our business, we sell both physical materials and services (one time and reoccurring charges). The current catalog schema has each distinct category broken out into individual tables, while this is nicely normalized and performs well, it is fairly difficult to extend. Adding a new attribute to a particular product involves changing the table schema and backpopulating old data. An idea I've been toying with has been something along the line of a base set of entity tables in 3rd normal form, these will contain the facts that are common among ALL products. Then, I'd like to build an Attribute-Entity-Value schema that allows each entity type to be extended in a flexible way using just data and no schema changes. Finally, I'd like to denormalize this data model into materialized views for each individual entity type. This views are what the application would access. We also have many tables that contain business rules and compatibility rules. These would join against the base entity tables instead of the views. My big concerns here are: Performance - Attribute-Entity-Value schemas are flexible, but typically perform poorly, should I be concerned? More Performance - Denormalizing using materialized views may have some risks, I'm not positive on this yet. Complexity - While this schema is flexible and maintainable using just data, I worry that the complexity of the design might make future schema changes difficult. For those who have designed product catalogs for large scale enterprises, am I going down the totally wrong path? Is there any good best practice schema design reading available for product catalogs?

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• choosing row (from group) with max value in a SQL Server Database

  - by sriehl

  I have a large database and am putting together a report of the data. I have aggregated and summed the data from many tables to get two tables that look like the following. id | code | value id | code | value 13 | AA | 0.5 13 | AC | 2.0 13 | AB | 1.0 14 | AB | 1.5 14 | AA | 2.0 13 | AA | 0.5 15 | AB | 0.5 15 | AB | 3.0 15 | AD | 1.5 15 | AA | 1.0 I need to get a list of id's, with the code (sumed from both tables) with the largest value. 13 | AC 14 | AA 15 | AB There are 4-6 thousand records and it is not possible to change the original tables. I'm not too worried about performance as I only need to run it a few times a year. edit: Let me see if I can explain a bit more clearly, imagine the id is the customer id, the code is who they ordered from and the value is how much they spent there. I need a list of the all the customer id's and the store that customer spent the most money at (and if they spent the same at two different stores, put a value such as 'ZZ' in for the store name).

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• NoSuchMethodError in Java using XStream

  - by Brad Germain

  I'm trying to save a database into a file using XStream and then open it again later using XStream and deserialize it back into the objects it was in previously. The database consists of an arraylist of tables, which consists of an arraylist of a data class where the data class contains an arraylist of objects. I'm basically trying to create an sql compiler. I'm currently getting a java.lang.NoSuchMethodError because of the last line in the load method. Here's what I have: Save Method public void save(Database DB){ File file = new File(DB.getName().toUpperCase() + ".xml"); //Test sample DB.createTable("TBL1(character(a));"); DB.tables.getTable("TBL1").rows.add(new DataList()); DB.tables.getTable("TBL1").rows.getRow(0).add(10); XStream xstream = new XStream(); //Database xstream.alias("Database", Database.class); //Tables xstream.alias("Table", Table.class); //Rows xstream.alias("Row", DataList.class); //Data //xstream.alias("Data", Object.class); //String xml = xstream.toXML(DB); Writer writer = null; try { writer = new FileWriter(file); writer.write(xstream.toXML(DB)); writer.close(); } catch (IOException e) { e.printStackTrace(); } } Load Method public void Load(String dbName){ XStream xstream = new XStream(); BufferedReader br; StringBuffer buff = null; try { br = new BufferedReader(new FileReader(dbName + ".xml")); buff = new StringBuffer(); String line; while((line = br.readLine()) != null){ buff.append(line); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } database = (Database)xstream.fromXML(buff.toString()); }

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• How can I stop an auto-generated Linq to SQL class from loading ALL data?

  - by Gary McGill

  DUPLICATE of http://stackoverflow.com/questions/2433422/how-can-i-stop-an-auto-generated-linq-to-sql-class-from-loading-all-data post answers there! I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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• How can I stop an auto-generated Linq to SQL class from loading ALL data?

  - by Gary McGill

  I have an ASP.NET MVC project, much like the NerdDinner tutorial example. (I'm using MVC 2, but followed the NerdDinner tutorial in order to create it). As per the instructions in part 3 of the tutorial, I've created a Linq-to-SQL model of my database by creating a "Linq to SQL Classes" (.dbml) surface, and dropping my database tables onto it. The designer has automatically added relationships between the generated classes based on my database tables. Let's say that my classes are as per the NerdDinner example, so I have Dinner and RSVP tables, where each Dinner record is associated with many RSVP records - hence in the generated classes, the Dinner object has a RSVPs property which is a list of RSVP objects. My problem is this: it appears (and I'd be gladly proved wrong on this) that as soon as I access a Dinner object, it's loading all of the corresponding RSVP objects, even if I don't use the RSVPs member. First question: is this really the default behavior for the generated classes? In my particular situation, the object graph contains many more tables (which have an order of magnitude more records), and so this is disastrous behaviour - I'd be loading tons of data when all I want to do is show the details of a single parent record. Second question: are there any properties exposed through the designer UI that would let me modify this behavior? (I can't find any). Third question: I've seen a description of how to control the loading of related records in a DataContext by using a DataShape object associated with the DataContext. Is that what I'm meant to do, and if so are there any tutorials like the NerdDinner one that would show not only how to do it, but also suggest a 'pattern' for normal use?

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• Doing large updates against indexed view

  - by user217136

  We have an indexed view that runs across three large tables. Two of these tables (A & B) are constantly getting updated with user transactions and the other table (C) contains data product info that is needs to be updated once a week. This product table contains over 6 million records. We need this view across these three tables for our core business process and unfortunately we cannot change this aspect. We even had a sql server MVP come in to help test under load to make sure we have the most efficient configuration. There is one column in the product table that gets utilized in the view and has to be updated each week. The problem we are now encountering is that as volume is increasing on our transactions against tables A & B, the update to Table C is causing deadlocks. I have tried several different methods to no avail: 1) I was hoping that we could change the view so that table C could be a dirty read "WITH (NOLOCK)" but apparently that functionality is not available with indexes views. 2) I thought about updating a new column in Table C and then just renaming it when the process is done but you cannot do that due to the dependency in the view. 3) I also entertained the idea of writing this value to a temporary product table, and then running an ALTER statement against the view to have it point to my new table. however when i did that the indexes on my view were dropped and it took quite a bit of time to recreate them. 4) we tried to do the weekly update in small chunks (as small as 100 records at a time) but we still run into dead locks. questions: a) we are using sql server 2005. Does sql server 2008 have a new functionality with their indexed views that would help us? Is there now a way to do dirty reads w/ an indexed view? b) a better approach to altering an existing view to point to a new table? thanks!

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• WPF Toolkit: Nullable object must have a value

  - by Via Lactea

  Hi All, I am trying to create some line charts from a dataset and getting an error (WPF+WPF Toolkit + C#): Nullable object must have a value Here is a code that I use to add some data points to the chart: ObservableCollection points = new ObservableCollection(); foreach (DataRow dr in dc.Tables[0].Rows) { points.Add(new VelChartPoint() { Label = dr[0].ToString(), Value = double.Parse(dr[1].ToString()) }); } Here is a class VelChartPoint public class VelChartPoint : VelObject, INotifyPropertyChanged { public DateTime Date { get; set; } public string Label { get; set; } private double _Value; public double Value { get { return _Value; } set { _Value = value; var handler = PropertyChanged; if (null != handler) { handler.Invoke(this, new PropertyChangedEventArgs("Value")); } } } public string FieldName { get; set; } public event PropertyChangedEventHandler PropertyChanged; public VelChartPoint() { } } So the problem occures in this part of the code points.Add(new VelChartPoint { Name = dc.Tables[0].Rows[0][0].ToString(), Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); I've made some tests, here are some results i've found out. This part of code does'nt work for me: string[] labels = new string[] { "label1", "label2", "label3" }; foreach (string label in labels) { points.Add(new VelChartPoint { Name = label, Value = 500.0 } ); } But this one works fine: points.Add(new VelChartPoint { Name = "LabelText", Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); Please, help me to solve this error.

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• SQL GUID Vs Integer

  - by Dal

  Hi I have recently started a new job and noticed that all the SQL tables use the GUID data type for the primary key. In my previous job we used integers (Auto-Increment) for the primary key and it was a lot more easier to work with in my opinion. For example, say you had two related tables; Product and ProductType - I could easily cross check the 'ProductTypeID' column of both tables for a particular row to quickly map the data in my head because its easy to store the number (2,4,45 etc) as opposed to (E75B92A3-3299-4407-A913-C5CA196B3CAB). The extra frustration comes from me wanting to understand how the tables are related, sadly there is no Database diagram :( A lot of people say that GUID's are better because you can define the unique identifer in your C# code for example using NewID() without requiring SQL SERVER to do it - this also allows you to know provisionally what the ID will be.... but I've seen that it is possible to still retrieve the 'next auto-incremented integer' too. A DBA contractor reported that our queries could be up to 30% faster if we used the Integer type instead of GUIDS... Why does the GUID data type exist, what advantages does it really provide?... Even if its a choice by some professional there must be some good reasons as to why its implemented?

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• Avoiding Duplicate Data in DB (for use with Rails)

  - by ants

  I have five tables that I am trying to get to work nicely together but may need some help. I have three main tables: accounts members and roles. With two join tables account_members and account_member_roles. The accounts and members table are joined by account_members (fk account_id and member_id) table. The other 2 tables are the problem (roles and account_member_roles). A member of an account can have more than one role and I have the account_member_roles (fk account_member_id and role_id) table joining the account_members join table and the roles table. That seems logical but can you have a relationship with a join table? What I'd like to be able to do is when creaeting an account, for instance, I would like @account.save to include the roles and update the account_member_roles table neatly ..... but through the account_members join table. I've tried ..... accept_nested_attributes_for :members, :account_member_roles in the account.rb but I get ..... ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection (Cannot modify association 'Account#account_member_roles' because the source reflection class 'AccountMemberRole' is associated to 'AccountMember' via :has_many.) upon trying to save a record. Any advice on how I should approach this? CIA -ants

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• UPDATE query that fixes orphaned records

  - by Jed

  I have an Access database that has two tables that are related by PK/FK. Unfortunately, the database tables have allowed for duplicate/redundant records and has made the database a bit screwy. I am trying to figure out a SQL statement that will fix the problem. To better explain the problem and goal, I have created example tables to use as reference: You'll notice there are two tables, a Student table and a TestScore table where StudentID is the PK/FK. The Student table contains duplicate records for students John, Sally, Tommy, and Suzy. In other words the John's with StudentID's 1 and 5 are the same person, Sally 2 and 6 are the same person, and so on. The TestScore table relates test scores with a student. Ignoring how/why the Student table allowed duplicates, etc - The goal I'm trying to accomplish is to update the TestScore table so that it replaces the StudentID's that have been disabled with the corresponding enabled StudentID. So, all StudentID's = 1 (John) will be updated to 5; all StudentID's = 2 (Sally) will be updated to 6, and so on. Here's the resultant TestScore table that I'm shooting for (Notice there is no longer any reference to the disabled StudentID's 1-4): Can you think of a query (compatible with MS Access's JET Engine) that can accomplish this goal? Or, maybe, you can offer some tips/perspectives that will point me in the right direction. Thanks.

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• Best practices for managing updating a database with a complex set of changes

  - by Sarge

  I am writing an application where I have some publicly available information in a database which I want the users to be able to edit. The information is not textual like a wiki but is similar in concept because the edits bring the public information increasingly closer to the truth. The changes will affect multiple tables and the update needs to be automatically checked before affecting the public tables. I'm working on the design and I'm wondering if there are any best practices that might help with some particular issues. I want to provide undo capability. I want to show the user the combined result of all their changes. When the user says they're done, I need to check the underlying public data to make sure it hasn't been changed by somebody else. My current plan is to have the user work in a set of tables setup to be a private working area. Once they're ready they can kick off a process to check everything and update the public tables. Undo can be recorded using Command pattern saving to a table. Are there any techniques I might have missed or useful papers or patterns? Thanks in advance!

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