I have a db (SQL Server 2008R2) and some common tables have to be moved out into another db because are going to be dictionary data for many clients. For compatibility reason is easy to have them in one place.
I can use synonyms, I tried and works!. My problem is about foreign keys, SQL Server does not support cross database foreign keys.
I can use triggers but is risky... is there any other workaround for this?
Related
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.
I'm working on the old C++ MFC project (> 10 years old). Database application works with migrating from MS Access (2007) to MS SQL Server (2008 R2) and I faced some hurdles on the way. For exporting data I used MS SQL Management Studio ("Import" option in the menu)
As it's known, there are some differences in data types between Access and MS SQL. That turned into some troubles.
Columns "ID" from Access (Autonumber, not NULL, primary keys) become just usual columns in SQL Server (int, not NULL and without any autoincrement). So I got lots of mistakes while inserting new rows into the tables.
Yes/No type in Access (-1/0; NULL is not allowed) becomes bit (1/0/NULL), logic of work shouldn't be broken as in the most of the places it is comparision of being not equal to 0:
query.Select()
.Buff("ID", &code)
.FromS("%Table_Name%", NULL)
.Where().Str("Aktiv <> 0")
.Execute();
Looking for a solution I saw the advice to use SSMA (SQL Server Migration Assistant) for Access. It's much better and more intellectual as it recreated primary/foreign keys, created CHECK's, indexes. But unfortunately lots of the FOREIGN KEYs' action Update/Delete operation become not Cascade but No Action. Warning message after schema import:
FOREIGN KEY constraint "Reference77" on MS Access table %Table1% may cause circular or multiple cascade paths. The cascade option from table %Table2% to table %Table1% was set to No option in SQL Server.
And that's not a surprise application gets some errors while deleting objects, though it was all OK in Access. For testing I selected one delete operation (in application) which got errors. I watched error messages and changed No Action -> Cascade for the involved FOREIGN KEYS via SSMS (SQL Server Management Studio). After that delete operation in the application succeeded.
My questions are:
Am I right I need only to change No Action -> Cascade for the FOREIGN KEYs to get the database application can work completely proper? Or there can appear another issues I don't know?
How can it be realized? I would like it to be a good solution for applying it on clients' SQL Servers.
Thanks for help, I really appreciate it!
Thanks for your answer. The solution for my problem is ... exporting data directly from Access (2010) to SQL Server.
I tried:
"SQL Server Import and Export Data", result - copying of only data from Access database, no any primary oк foreign keys, no transformation of autonumber to a column with IDENTITY and autoincrement.
SQL Server Migration Assistant for Access, result - a lot of foreign keys lost CASCADE property for update/delete operations. But all another things are OK.
Access 2010! Database Tools -> SQL Server -> ... using wizard -> all is OK with schema and data. Application works fine with the SQL Server database imported from Access.
So direct export from Access to SQL Server gave the required result.
Probably, but you will still need to test.
For a reusable solution, I would script the database that SSMA created (checking that all the types and foreign keys are correct). Having this script you can create an empty SQL Server database on any number of servers.
To populate these databases I'd use an Integration Services package. It's very easy to create by using Import wizard: going thru all the steps, but saving the package instead of running it immediately. Then you can open this package and edit it (adding data conversions or any other logic if necessary).
When I'm importing data from SQL Server 2008 DB to another using SSMS 2008, I get errors during the importation because it tries to insert data in a "read only" fields, or cuz some conflicts of relationships between tables' keys.
I'm wondering, how could I close the eyes of the SSMS until he finish the transformation :D
Thanks, Regards
Yes, if you reorder your table data insert statements you should be able to resolve foreign key/relationship issues. You could use an ER diagram (e.g. in SSMS Database Diagrams, select all tables) to first insert the data for the tables other tables depend on/point to with foreign keys, and then work your way down the dependencies.
I wonder how you generated these scripts; I'd imagine that any tool worth it's salt would generate data insert scripts in the proper order.
What's the best practice for handling primary keys using an ORM over Oracle or SQL Server?
Oracle - Should I use a sequence and a trigger or let the ORM handle this? Or is there some other way ?
SQL Server - Should I use the identifier data type or somehow else ?
If you are using any kind of ORM, I would suggest you to let it handle your primary keys generation. In SQL Server and Oracle.
With either database, I would use a client-generated Guid for the primary key (which would map to uniqueidentifier in SQL Server, or RAW(20) in Oracle). Despite the performance penalty on JOINs when using a Guid foreign key, I tend to work with disconnected clients and replicated databases, so being able to generate unique IDs on the client is a must. Guid IDs also have advantages when working with an ORM, as they simplify your life considerably.
It is a good idea to remember that databases tend to have a life independent from a front end application. Records can be inserted by batch processes, web services, data exchange with other databases, heck, even different applications sharing the same database.
Consequently it is useful if a database table is in charge of its own identify, or at least has that capability. For instance, in Oracle a BEFORE INSERT trigger can check whether a value has been provided for its primary key, and if not generate its own.
Both Oracle and SQL Server can generate GUIDs, so that is not a sufficient reason for delegating identity generation to the client.
Sometimes, there is a natural, unique identifier for a table. For instance, each row in a User table can be uniquely identified by the UserName column. In that case, it may be best to use UserName as the primary key.
Also, consider tables used to form a many to many relationship. A UserGroupMembership table will contain UserId and GroupId columns, which should be the primary key, as the combination uniquely identifies the fact that a particular user is a member of a particular group.
I've just come across something disturbing, I was trying to implement transactional replication from a database whose design is not under our control . This replication was in order to perform reporting without taxing the system too much. Upon trying the replication only some of the tables went across.
On investigation tables were not selected to be replicated because they don't have a primary key, I thought this cannot be it is even shown as a primary key if I use ODBC and ms access but not in management studio. Also the queries are not ridiculously slow.
I tried inserting a duplicate record and it failed saying about a unique index(not a primary key). Seems to be the tables have been implemented using a unique index as oppose to a primary key. Why I do not know I could scream.
Is there anyway to perform transactional replication or an alternative, it needs to be live (last minute or two). The main db server is currently sql 2000 sp3a and the reporting server 2005.
The only thing I have currently thought of trying is setting the replication up as if it is another type of database. I believe replication to say oracle is possible would this force the use of say an ODBC driver like I assume access is using hence showing a primary key. I don't know if that is accurate out of my depth on this.
As MSDN states, it is not possible to create a transactional replication on tables without primary keys. You could use Merge replication (one way), that doesn't require a primary key, and it automatically creates a rowguid column if it doesn't exist:
Merge replication uses a globally
unique identifier (GUID) column to
identify each row during the merge
replication process. If a published
table does not have a uniqueidentifier
column with the ROWGUIDCOL property
and a unique index, replication adds
one. Ensure that any SELECT and INSERT
statements that reference published
tables use column lists. If a table is
no longer published and replication
added the column, the column is
removed; if the column already
existed, it is not removed.
Unfortunately, you will have a performance penalty if using merge replication.
If you need to use replication for reporting only, and you don't need the data to be exactly the same as on the publisher, then you could consider snapshot replication also