Find identity on a table

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  1. SQL Server – Multiple ways to find identity column | SQL Server Portal
  2. Introduction
  3. Introduction to Oracle identity column
  4. Working With Identity Column After Table Creation In SQL Server

Assuming you started at zero or 1, this gives you another 2 billion values to use. The change will require the table to be locked, lots of transaction log will be generated, etc. The path of least resistance and least or no downtime is to reseed the identity column.


This is virtually instantaneous. To answer this question, you need to know where the gaps in your used identity values are. I went searching for some code to do this and came across this solution from Microsoft:.

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Looks like my table has too many gaps for this to be a valid solution. So back to Google I went and found this really nice solution from Henning Frettem. When I ran his code, I saw my table had 97, gaps! So which should I use? Ideally, the largest one! In my case, someone had already reseeded the table to negative numbers in the past, so my developers were OK with using negative numbers.

If you encounter this problem and are unable to change the datatype, you now have the code to find the largest gap to use when reseeding your identity value! Your email address will not be published. Notify me of followup comments via e-mail.

SQL Server – Multiple ways to find identity column | SQL Server Portal

Or if you're constantly using their location, or It should be something that you need frequently and don't want to look up in your own tables by ID as the previous example showed. You could then use that to look up a user in your own tables with a Find since it would likely be a primary key. So how do you get your data in to these Identity tables?

Our strategy is to do the same thing but instead of running a database update migration we do the update to the database ourselves. But it doesn't yet exist in the database. Well, that's easy to fix: add that to your db script that creates the Identity tables. Or, for something this simple you can additionally! Creating a statement to alter the table to its new configuration is in fact precisely one of the things that migrations do.

In fact here's the SQL it generates for exactly this addition:. Now you can give that attribute a value e. As with 1 above, with this model you do not generate model classes for the Identity tables. You'll use a separate DbContext class for your own tables. So you're going to roll the dice and integrate everything with one context?


Ok, let's roll. In this example we will create a new table that has a foreign key to the Identity table's Id, and we'll use the same context as Identity. We'll have a navigation property from ApplicationUser to this new table as well as a navigation property from the new table to ApplicationUser. Here's the new table. We start by defining the database, as is usual with the database-first approach. I'll make this one different than in 1 to keep them easily separated. If both entities are unique a relationship would be more realistic. Let's assume this one is more general in that a logged in and authorized user might, for some reason, want to or need to have zero or multiple MyUsers.

We can execute this script and create the database. But our application won't know anything about it until we reverse engineer or simply write -- it isn't that hard for one class the model class and tell it to use this relationship properly. Reverse engineering the model isn't difficult, just make sure and exclude the AspNet tables -- those are already taken care of by the Identity system. We just want our class and the changes that are needed to the context class.

So here's what we do. Reverse engineer the model and use a throw-away name for the new context that get's generated. Throw away that context class as well as the connection string that has just been generated. Before you throw away the context class take a look at it to see if there's anything interesting in there. Actually you don't have to throw it away, just don't use it. The ORM won't give you the navigation property. I'm not sure if this is because we didn't import the AspNetUsers table probably or if it's because the name is remapped somewhere within Identity possibly?

That's for the 1 side of the 1:N relationship, i. BTW: Don't call this entity User with an associated table called Users because that already exists in Identity see above.

Introduction to Oracle identity column

Unfortunately that's not quite it. Since we're not using the context class that EF created for us we need to update the Identity version of the context. To get the new MyUser into the database with the relation set correctly I had to modify RegisterViewModel to add in the first and last names, then edit the View to add those text fields, and finally the account controller to create the objects and save to the database:.

Now you can continue to build out your models. Just remember that when you generate your models you must manually update the ApplicationDbContext class yourself. NET Identity. Strategies Here are a few strategies you can take from this point for your software design.

Working With Identity Column After Table Creation In SQL Server

Keep everything separate. Make no changes to the Identity database i. Modify only a bit. Make a few small changes to the Identity database but essentially keep it separate from your application. This means adding columns to Identity tables but not forming any relations between the Identity tables and your own. For example, you might add a pseudonym, or zip code, or some other simple user attributes. You'll still have a separate database context and connection string. Integrate everything. Make changes to the Identity database and form relations between it and your tables, and vice versa.

With this model you can use a single database context class and connection string. Sure, you can always use a separate database but you don't have to. Let's look at each one in some depth 1. Look in AccountController for how to get one: HttpContext. Normally use [Authorize] attribute on the class or method. FindById "thor gmail. Users i. AspNetUsers " ; foreach var item in db.

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