If I have two databases and create a linked table (synonym) in one of them to the other one and then wrap that synonym in a view, will there be a performance issue? The reason I want to do this is to have SQLMetal see the synonym and generate a linq entity for it. The database are on the same server. Also if I did this 100+ times, all child databases linking to a set of tables in a master database, would that have a problem?
Nah - shouldn't be an issue. The Query Optimizer says "What do you mean by this" all the time, and unless it comes across a procedure (or function with BEGIN/END), it'll keep going. Synonyms are fine, views are fine.
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I'm working on migrating application from Access to Oracle and have faced with a strange issue . So we have a regular oracle schema - nothing fancy. on the top of that schema I created a number of views - approximately 15. These views use each other and dependency tree can be deep - I'd say up to 6-8 levels.
So now I faced with an issue when I cannot create another view - CPU at oracle servers goes to 50% when I execute 'create or replace view' statement and it takes forever. Views are right now in such a state that selection data from these views may take time, but the issue appears in 'create' statement. I'm not using 'select * ...' in the views and the problematic view depends just on two others.
I'm using Oracle 10g Enterprise v 10.2
In SQL Server I'm familiar with Profiler and would do a trace, view schema locks, but I don't know Oracle that much.
Will appreciate any hints. Thank you.
Views referencing views referencing views strikes me as highly unnecessary. I know we're all supposed to be in favour of "don't repeat yourself" but DRY is a guideline, not a cast-iron rule. It's certainly not intended to be applied so compactly in a database context that nothing compiles.
So try separating out all the views, so that each one references only tables in the FROM clause. That should solve your problem and allow you to make progress with your code.
You can always review the situation later. The neat thing about a view is that it is just an interface. If you subsequnetly want to refactor some views, to replace tables with views than you will be able to, with the minimum of inconvenience (unless you re-introduce the compilation hang).
First of all I won't to say that I'm an expert in database handling, and less so in oracle. However right now I need to get better at it :)
I'm using nHibernate as orm, to my oracle database. It works ok, and is rather simple to use. However now I have run in to a problem that I don't know how to solve.
In the Database theres a kind of tree with the tables, views, indexes and such. At the end there are also a entry called "Other Users" in which there are some users with access to what I'm guessing is other tables. Now I would like to get data from one of those tables (I can read them manually in SQL Developer, so it's not a access problem or anything). Does anyone have any idea how I shall do that?
The account that you use in SQL Developer has at least read privilges to tables in another schema (owned by another user). You can access these tables by prefixing the table name with the schema name. In Hibernate you'll have to define the non-default-schema in the mapping.
I'm building a project combined of number of sites with common subject.
The sites rely on one central database that holds the common info for all of them.
In addition, each site has another database that holds its unique info (I will refer to it as unique-db in the next lines so I won't be misunderstood).
For example, the Languages table sits in the central db. That said, I suddenly noticed that I need to use the Languages table in one of my unique-db in order for the table to act as a FK so I don't have to create the same table again in the unique-db.
Do I have to create the same table again this time in the unique-db? Or is there a way to connect tables from separate databases?
In addition, we decided using linq2entity and soon we're gonna run some complex queries against the different databases. Will I have a problem with this matter?
How should I go on with that? Was it wise to split the data into a few databases?
I really appreciate all the help I can get!
One thing that might make your life easier is to create views of the central tables in each unique db. Linq to Entities will pick up views as if they were tables.
Is it possible to create a view in a database A of tables of another database B? If possible, can somebody please help me, I'm totally clueless.
Of course, just use a database link. So, your view would be:
create or replace view my_view as
select some_columns
from my_table#the_other_database
Beware though it's not always that efficient and you may have some problems with queries doing things you don't expect. If there's any volume to the data you're trying to select it might be worth using a materialized view instead to take data cross server. Then you can select data from the server you're on currently, which'll probably be a lot quicker.
I've got two tables that need to be joined via LINQ, but they live in different databases. Right now I'm returning the results of one table, then looping through and retrieving the results of the other, which as you can guess isn't terribly efficient. Is there any way to get them into a single LINQ statement? Is there any other way to construct this to avoid the looping? I'm just looking for ideas, in case I'm overlooking something.
Note that I can't alter the databases, i.e. I can't create a view in one that references the other. Something I haven't tried yet is creating views in a third database that references both tables. Any ideas welcome.
You can do this, even across servers, as long as you can access one database from the other. That is, if it's possible to write a SQL statement against ServerA.DatabaseA that accesses ServerB.DatabaseB.schema.TableWhatever, then you can do the same thing in LINQ.
To do it, you'll need to edit the .dbml file by hand. You can do this in VS 2008 easily like this: Right-click, choose Open With..., and select XML Editor.
Look at the Connection element, which should be at the top of the file. What you need to do is provide an explicit database name (and server name, if different) for tables not in the database pointed to by that connection string.
The opening tag for a Table element in your .dbml looks like this:
<Table Name="dbo.Customers" Member="Customers">
What you need to do is, for any table not in the connection string's database, change that Name attribute to something like one of these:
<Table Name="SomeOtherDatabase.dbo.Customers" Member="Customers">
<Table Name="SomeOtherServer.SomeOtherDatabase.dbo.Customers" Member="Customers">
If you run into problems, make sure the other database (or server) is really accessible from your original database (or server). In SQL Server Management Studio, try writing a small SQL statement running against your original database that does something like this:
SELECT SomeColumn
FROM OtherServer.OtherDatabase.dbo.SomeTable
If that doesn't work, make sure you have a user or login with access to both databases with the same password. It should, of course, be the same as the one used in your .dbml's connection string.
Create a proc/view in your database.
Given your conditions, I don't think you can do this in one Linq statement. But you can join the results of your L2S queries into a Linq to Objects query.