EDIT: This question was based on the incorrect premise that SQL VIEWS were cleared from a database when the user that created them disconnects from the server. Leaving this question in existence in case others have that assumption.
I'm trying to use views in my database, but I'm running up against an inability to save the code as a SQL Server object for repeated use.
I tried saving CREATE VIEW statements as procedures and user defined functions, but as many have answered on stack overflow, CREATE PROCEDURE and CREATE FUNCTION are incompatible with CREATE VIEW due to the only one in batch issue.
Obviously I don't want to retype my CREATE VIEW statements every time, and I'd prefer not to have to load them from text files. I must be missing something here.
You don't really "save" CREATE/ALTER statements. The create or alter statement changes the structure of the database. You can use SSMS to generate the statement again later by right clicking on the view, and choosing Script as->Create. This inspects the structure of the database and generates the statement.
The problem with this approach is your database now consists of both a structure definition(DDL) as well as its contents, the data. If you dropped/created the database to clear its data, you'd also have lost the structure. So you always need a database hanging around for the structure and back it up to ensure you don't ever lose the DDL.
Personally I would use Database Projects as part of Visual Studio and SQL Server Data Tools. This allows you to keep each View, Table, etc. as separate files, and then update the database using schema compare. The main benefit being you can separate the definition of the database from the database itself, and also source control or backup the DDL files.
If you really want to, you could create a view in a proc like this:
CREATE PROCEDURE uspCreateView AS
EXEC('CREATE VIEW... ')
Though, you'll have to escape single quotes in your view code with ''
However, I have to agree with the other comments that this seems like a strange thing to do.
Some other thoughts:
You can use sp_helptext to get the code of an existing view:
sp_helptext '<your view name here>'
Also, INFORMATION_SCHEMA.VIEWS includes a VIEW_DEFINITION column with the same code:
SELECT * FROM INFORMATION_SCHEMA.VIEWS
Related
I have a a system with two databases, main database and audit database. A lot of the triggers and table views in the main database and audit database are referencing from one database to the other. No I needed to change both databases names but unfortunately they failed to work because they still have the old names in the code.
Is there a code to search and replace the old name used for referencing or in dependence?
Thank you,
You will have to manually fix the references but you can leverage some sql to find the offending objects.
select OBJECT_NAME(id) as ObjectName
, text as ObjectCode
from sys.syscomments
where text like '%YourReplacedDatabaseName%'
That will give you a list of functions, procedures, views etc that have the old database name in the code. You will however have to recompile each object after you have updated the code. You could probably utilize some dynamic sql around this to do it for you but I would be nervous about changes on that scale automatically.
I recently used - EXEC sp_rename '<source table name>', '<destination table name>' to rename an existing table and want to execute the same on one of our live server. Is there any issue in using this procedure to rename a table?. I am asking this because one of our DBA says there will be problems in using this procedure on live server.
Is nothing referencing the table you're renaming? That would be the only instance where I would think renaming the table would not have an impact. If the table was not referenced by anything however, what would be the purpose of the table?
you can read more about sp_rename here:
http://msdn.microsoft.com/en-us/library/ms188351.aspx
Specifically note the following:
Renaming an object such as a table or column will not automatically
rename references to that object. You must modify any objects that
reference the renamed object manually. For example, if you rename a
table column and that column is referenced in a trigger, you must
modify the trigger to reflect the new column name. Use
sys.sql_expression_dependencies to list dependencies on the object
before renaming it.
There is no major issue with renaming the table using that procedure. The only thing you need to remember is that while that command is being executed, the locks that are applied on that table won't allow you to query the data, but that should only take only a couple of milliseconds, so you should be fine.
P.S. Don't forget to modify your views, procedures, functions etc :)
Below is the only caution as described inthe microsoft official web site.
Changing any part of an object name can break scripts and stored procedures. We recommend you do not use this statement to rename stored procedures, triggers, user-defined functions, or views; instead, drop the object and re-create it with the new name.
More details at : http://msdn.microsoft.com/en-us/library/ms188351.aspx
EXEC sp_rename is recommended only when we sure that all the depended SP, View function are not get affected. Make sureyou changed or deleted the depended objects.
Perhaps your DBA can share the details of his/her concerns. Renaming a table will of course be a breaking change for any objects that reference the table so you'll need to perform due diligence to ensure dependent objects are changed to use the new name. The rename operation will also require a short schema modification lock and void existing referencing cached plans, so be aware of this if the table is heavily used.
I'm creating an Oracle view like this :
SELECT * FROM TABLE;
When I create the view, I notice that oracle changes the view query to something like :
SELECT FIELD1, FIELD2,... FROM TABLE;
My problem is that if I change the TABLE structure, add a new field for instance, the changes are not taken into consideration in the view. I have then to recreate the view, and regrant privileges on this view to the users/roles.
Is there any way to make a view mode generic and keep it as the form of : SELECT * FROM TABLE ?
Thanks.
You cannot define a simple view that would automatically change its structure when the underlying table changes. When new columns are added, you'll need to touch the view. You'll almost certainly need to do as #GordonLinoff suggests and do a CREATE OR REPLACE when the table changes. Given that changes to tables should be rare and should involve proper change control, touching the view as part of the change should be a relatively simple step.
If you're really determined to avoid having to touch the view, there are some alternatives. I generally wouldn't recommend these because they are very likely to increase rather than decrease the complexity of maintaining your system. But if you have a third party system that is generating DDL to add columns on an unpredictable basis, maybe it makes sense.
You could create a DDL trigger that fires in response to statements that ALTER the table and that submits a job using dbms_job that re-creates the view. That's quite a few moving pieces but it's generally workable.
Alternately, instead of a view, you could create a pipelined table function that returns a variable number of columns. That's going to be really complicated but it's also pretty slick. There aren't many places that I'd feel comfortable using that approach simply because there aren't many people that can look at that code and have a chance of maintaining it. But the code is pretty slick.
The * is evaluated when the view is created, not when it is executed. In fact, Oracle compiles views for faster execution. It uses the compiled code when the view is referenced. It does not just do a text substitution into the query.
The proper syntax for changing a view is:
create or replace view v_table as
select *
from table;
I have face this same issue and created a procedure which accepts the name of the table and creates the view:
str := 'create or replace view xyz.'|| tablename_in ||'_v as select * from '|| tablename_in;
execute immediate str;
Then in Toad (not sure if you use Toad), in the schema browser, right click on the table name, and then select 'Custom Queries' --> 'Edit Custom Queries' and then have it call your procedure as:
exec view_create<ObjectList>
Then you can right click on the table name and in one click create the view as Toad will pass the name of the table into the procedure.
Also in the procedure you may want to recompile the schema, so after the view is created do:
sys.utl_recomp.recomp_parallel(4, 'XYZ');
If you develop a script of some sort which can semi automate, it makes things easy.
Hope this helps...
I know databases aren't supported by CREATE SYNONYM, but I'm looking to achieve the functionality this would provide.
We've got Database A which contains views to tables on Database B. The trouble is "Database B" isn't always called "Database B". We use database projects for deployments, which at the moment fall over with an "Invalid Object Name" error if there isn't a "Database B".
The workaround at the moment is to open up the .dbschema file and do a find and replace. I guess another option would be to create a load of table synonyms.
What's the best way of changing the database a number of views reference without changing each view individually?
Thanks
Synonyms are a good way to do this. You have to create the synonyms at the object level though (as you've discovered). An easy way to do this would be to write a script that runs through the list of tables in DatabaseB (from your example) and creates a synonym for each one in DatabaseA. Keep the name of the synonym the same so the code in your views doesn't have to change. For instance, you you have tbl_a, tbl_b, and tbl_c in DatabaseB, you'd want your script to eventually do the following:
create synonym [otherDb].[tbl_a] for [DatabaseB].[schemaB].[tbl_a]
create synonym [otherDb].[tbl_b] for [DatabaseB].[schemaB].[tbl_b]
create synonym [otherDb].[tbl_c] for [DatabaseB].[schemaB].[tbl_c]
Now, in your view code, you'll always use [otherDb].[tbl_a], [otherDb].[tbl_b], and [otherDb].[tbl_c]. Hope this makes sense.
Last year I helped my current client with the implementation of a very similar design. We wrote a set of functions and stored procedures which generate the views automatically. Whenever you need to change the target database it generates the code to drop and recreate all of the views.
The code wasn't too difficult. It just uses the system tables to generate view code. I also wrote a Powershell prototype that uses SMO to do the same thing. The key is to have it automated to the point of requiring a single call so that you can do it easily and accurately.
We also included an exception table that used a pattern match of tables to exclude from view generation. It included a schema column and a table name column, each of which accepted LIKE patterns, so you could put "my_schema" and "%" to exclude all tables in the my_schema schema.
One master stored procedure accepted a target database name and would generate the entire script. Once the script is generated you can run it in SSMS or have that part automated as well.
This whole thing would be even easier if you just wanted to generate synonyms. We were using views so that we could change column lists, etc. and have the view DB look different than the target DB where needed.
If we want to change the name of MyColumnName to MyAlteredColumnName...
...and we have a SQL Server 2008 table that looks like:
MyTable
MyColumnName
and a view that references the underlying column:
CREATE VIEW MyDependentView WITH SCHEMABINDING
AS
SELECT ..., MyTable.MyColumnName
We end up following this procedure:
Dropping the View
Altering MyTable.MyColumnName to MyTable.MyAlteredColumnName
Recreating the View with a reference to MyAlteredColumnName
We do this with migrator dot net.
Is there a better way to do this? Is there T-SQL that will alter a view column name? Or any support in SQL Server 2008 for automagically tying the columns together?
Without the use of a third-party tool, this is one of the only ways to do it. You can obviously also use ALTER VIEW instead of a DROP and CREATE.
It should be noted that Red-Gate makes a tool called SQL Refactor which will automate this sort of change (no I do not work for them). I'm sure there are other similar database refactoring tools out there.
Use sp_refreshview:
EXEC sp_refreshview #viewName
If you want to refresh all your views, you'll have to iterate over a loop of them, which means dynamic SQL.
And if you layered them (a view is dependent on another view - bad), you'll have to refresh the parent first...
If it's a SELECT * view, you can call sp_refreshview, as OMG_Ponies suggested. It will recompile the view and update the column metadata appropriately. This is one area where judicious use of SELECT * could have benefits, if used appropriately within a coherent scheme.
Otherwise, you must redefine the view. Any explicit references to the old column name will now raise an error.
Ah, one more alternative:
EXEC sp_rename 'MyTable.MyColumnName', 'MyAlteredColumnName'
ALTER TABLE MyTable ADD MyColumnName AS MyAlteredColumnName
EXEC sp_rename 'MyView.MyColumnName', 'MyAlteredColumnName'
It's a hack, and it's dangerous, since the stored view definition will now be out of sync with the view metadata. And you have littered the db with superfluous computed columns.
But it will work (until you forget what you did, or someone else has to maintain the system, and things start to break mysteriously).
I use a third party tool for this, it hasn't failed me yet. It's ApexSQL Refactor, here's the how-to tutorial
How to rename a column without breaking your SQL database