I'm am currently developing one project of many to come which will be using its own database and also data from a central database.
Example:
the database "accountancy" with all accountancy package specific tables.
the database "personelladministration" with its specific tables
But we also use data which is general and will be used in all projects like "countries", "cities", ...
So we have put these tables in a separate database called "general"
We come from a db2 environment where we could create foreign keys between databases.
However, we are switching to MS SQL server where it is not possible to put foreign keys between databases.
I have seen that a workaround would be to use triggers, but I'm not convinced that is a clean solution.
Are we doing something wrong in our setup? Because it seems right to me to put tables with general data in a separate database instead of having a table "countries" in every database, that seams difficult to maintain and inefficiënt.
What could be a good approach to overcome this?
I would say that countries is not a terrible table to reproduce in multiple databases. I would rather duplicate static data like that than use more elaborate techniques. There is one physical schema per database in sql server and the schema can not be shared. That is why people use replication or triggers for shared data.
I can across this problem a while back. We have one database for authentication, however, those users have to be shared across multiple applications some of which have their own database.
Here is my question on this topic.
We resorted to replication and using an custom Authentication/Registration service agent to keep the data up to data.
Using views, in what Sourav_Agasti suggested in his answer, would be the most straight forward approach for static data. You can create views and indexed views and join data from databases on linked servers.
Create a loopback linked server and then create a view(if required, on each database) which accesses the table in this "central database" through this linked server. There will be a minor performance impact but it more than enough compensates by being very simiplistic.
Related
. I have two databases in same azure sql server .i want that both database interact to each other using trigger. i.e If any record is inserted in Customer table of first database the trigger gets fired and record is inserted in another database.
We had / have the same problem with triggers that we use for insert-update-delete where we write a record to Database-1 that has the primary table, but also updates Database-2 where we hold "archive" versions of the tables.
The only solution we have identified and are testing is to bring all of the tables into a single database and separate the different tables under separate database schemas in the one database.
Analysis so far of this approach looks promising.
I think what you're trying to do is not allowed in Sql Azure. From my expertise what you are trying to do is a bad practice on-premise as well (think backups-restore and availability issue scenarios).
You should move the dependency in the application and have the application update both databases, as appropriate.
Anyway, if you want to continue with this approach please take a look over Elastic Query feature: https://learn.microsoft.com/en-in/azure/sql-database/sql-database-elastic-query-overview
Please let me know if I can help with something
I have shared resources across all of my databases. Users, Companies etc. These are shared between all of my databases and the tables are the same. I want to create on Database for these tables and have all of my databases reference this one instead of having multiple tables that are the same. I come from a C# background and I am not very proficient in SQL. I am writing a new application that uses several of the databases we have.
Question: Should I make one database an authoritative source on these resources? The problem I see is I need Foreign Key relationships between databases and without triggers this is not possible. Not to mention when I write my linq statements I cannot query by these items.
We were able to achieve this by having one central database as the source of truth, then having copies of the applicable tables moved out to all the databases that needed it via triggers. You have to make sure all CRUD is done to the source of truth database, otherwise it gets very complicated to manage everything. You can then create the foreign keys to the copy tables.
Is it possible to define relationships between tables in different databases in SQL server 2008? And can you recommend an online tutorial for studying it? (I prefer ASP.NET, C#)
No, you can't have foreign keys between databases.
Data integrity is within a single database only. If you need transactional consistency across databases then you should use a single database. The main issue is backups/restores: you will end up with broken data after a restore because your backups are not consistent.
A recent blog article "One Database or Ten?" explains in more details
Saying that, you can use triggers if you need this and are prepared to have broken data
Yes you can but NOT using FOREIGN KEYS:
You can use specific stored procs, which checks the consistency - in
this case you have to make the user to use only these procedures for
all the CRUD operations in both DBS
Triggers, which will check the same
All of the above have to run within properly isolated transaction to
be sure, that your "just checked" values will not be deleted in a
moment
I’m after a bit of advice on the best way to go about this is SQL server 2008R2 express. I have a number of applications that are in separate databases on the same server. They are all “plugins” that use a central staff/structure list that will be in a separate database. The application is in the process of being migrated from JET.
What I’m looking for is the best way of all the “plugin” databases being able to see the central database and use those tables in standard queries and views etc.
As I’m using express that rules out any replication solution and so far the only option I can think of is to use triggers or a stored procedure to “push” out all the changes to the plugins. The information needs to be populated on a near enough real time basis however the number of changes will be very small maybe up to 100 a day and the biggest table only has about 1000 rows at the moment (the staff names table).
Hopefully that will cover all everything but if anyone needs any more details then just ask
Thanks
Apologies if I've misunderstood, but from your description it sounds like all these databases are hosted on the same instance of SQL Server - it's your mention of replication that makes me uncertain.
Assuming that's the case, you should be able to replace any copies of tables from the central database which are held in the "plugin" databases with views or synonyms which reference the central tables directly, since SQL server allows you to make references between databases on the same server using three-part naming (database_name.schema_name.object_name)
For example, if each plugin db has a table StaffNames, you could replace this with a view by dropping the table, then creating a view:
drop table StaffNames
go
create view StaffNames
as
select * from <centraldbname>.<schema - probably dbo>.StaffNames
go
and your code should continue to work seamlessly, as long as permissions are set up.
Alternatively, you could replace all the references to the shared tables in the plugin databases with three-part name references to the central database, but the view method requires less work.
I've been tasked with revisiting a database schema we designed and use internally for various ticketing and reporting systems. Currently there exists about 40 tables in one Oracle database schema supporting perhaps six webapps.
However, there's one unifying relationship amongst them all: a rooms table describing the room. Room name, purpose and other data are thrown into a shared table for each app. My initial idea was to pull each of these applications into a separate database, and perform joins between a given database and the room database. But I've discovered this solution prevents foreign key constraints in SQL Server 2005. It seems silly to duplicate one table for each app and keep those multiple copies synchronized.
Should I just leave everything in one large DB, or is there something else I can do separate the tables without losing FK constraints?
The only way to achieve built-in referential integrity is to have the table inside the database in which it is referenced. You might be able to achieve the equivalent of referential integrity using triggers but it would likely be deathly slow.
You might be able to use SQL Server replication, in it's "Transactional replication" mode/form. http://msdn.microsoft.com/en-us/library/ms151176.aspx
if all the apps truly use and depend on the rooms - then keep them all in one DB.
you can still set privilege on the tables properly, and manage the data sets in the non overlapping areas normally -
is there any task you imagine you will not be able to perform when things are together?