I'm new to Azure and not great with SQL so any help would be greatly appreciated.
I have a Database where each user has a Schema. Each Schema has identically structured tables with the same name, say "Table".
I now require a View in another Schema which provides a read-only union of all the rows from all the tables Table.
I was successful in creating a Schema, say Views, handling its permissions and creating a View, "TableView", with the following SQL from Partitioned Views # learn.microsoft.com:
CREATE VIEW Views.TableView
AS
SELECT *
FROM Schema1.Table
UNION ALL
SELECT *
FROM Schema2.Table
UNION ALL
SELECT *
FROM Schema3.Table
...
GO
I now wish for this View to be dynamic as future Schemas (SchemaX) are added or even possibly removed without having to repeatedly DROP and CREATE TableView over and over.
Is it possible to create the View in such a way that it would automatically query all tables with the same name? Or perhaps there is some way to 'add' an additional table post creation?
I can get a list of all SchemaX.Table by querying INFORMATION_SCHEMA, but other than having a python script DROP and CREATE the View again I am lost.
Thanks
Thanks for #larnu's comments, it's very useful and professional:
To achieve this dynamically, it would be impossible to do in a VIEW.
You would have to use a stored procedure, and that means you can't do
simple things like SELECT from it, making it far harder to use.
Instead of having 17 tables, all identical, on different schemas you
have one table, with a column BusinessName. Instead of
MySmartCompany.Mytable you have a column in the table dbo.MyTable (or
your generic schema), called BusinessName which has the value 'MySmartCompany'.
This also can be beneficial to other community members.
Related
I have two different databases. Let's say 'DbOne' and 'DbTwo'.
Is there any way to do the followings?
Create a view in DbOne
Transfer data in a particular table from DbTwo to the newly created view in DbOne.
I am using SSMS and still figuring out the appropriate query..
Please give me any advice.
You need INSERT / SELECT statement - eg.
INSERT INTO DbOne..NewView
SELECT * FROM DbTwo..SourceTable
However, depending on the structure of both tables, you may need to specify the particular columns in the SELECT statement, to match the structure of the target table. (By the way, note that data is always going into a TABLE - not a VIEW. You can do an INSERT into a VIEW, but only under certain conditions)
I want to query an object from DB that exists in any one of the tables. I am not sure about the table name that a particular object belongs to. For e.g. let's say my DB consists of various tables like Domestic_Passengers, Asian_Passengers, US_Passengers. And this table list may increase as well like in the future we may add the UK_Passengers table too.
So, I want to query something like
SELECT * FROM
(SELECT table_name FROM user_tables where table_name like '%PASSENGER')
WHERE NAME LIKE 'John%'
Is this possible?
That's a very bad database design.
I would suggest a view like this:
CREATE OR REPLACE VIEW PASSENGERS AS
SELECT * FROM Domestic_Passengers
UNION ALL
SELECT * FROM Asian_Passengers
UNION ALL
SELECT * FROM US_Passengers;
And then select from this view.
If this is not possible, then you need to run dynamic SQL in PL/SQL package. But this involves some code.
The best answer depends on a lot of details, such if you can create database objects, how static are the tables, and how will this query be consumed.
If you can create schema objects, and the list of tables is somewhat stable, then Wernfried's answer of building a view is probably best.
If you can create schema objects, but the list of tables is very dynamic, and your application understands ref cursors, you should probably create a function that creates the SELECT and returns it through a ref cursor, like in this answer.
If you cannot create schema objects, then you're limited to the DBMS_XMLGEN/XMLTABLE trick. In a single query, build a string for the SELECT statement you want, run it through DBMS_XMLGEN to create an XMLType, and then use XMLTABLE to transform the XML back into rows and columns. This approach is slow and ugly, but it's the only way to have dynamic SQL in SQL without creating any custom PL/SQL objects. See my answer here for an example.
We have a table in our Oracle Database that was created from an actual script.
Ex:
Create Table AS (Select * from table).
I was hoping to recover the original script the table was created from as the data is quite old in the table, but needs this created table needs to be refreshed. This table is created with data from another live table in our database, so if there is a way to refresh this without the original query - I'm open ears. Any solutions are welcomed!
Thanks!
I suppose you could also do a column by column comparison of this table against all others to see which one (if any) matches it. Of course, this would only be a guess.
It would require that object to actually be a materialized view instead of a table. Otherwise you are probably left off with exploring logs. Beyond that I doubt there is any way to recover the original select statement used to create that table.
I want users to SELECT and Modify Data trough a view, but give no permissions to the base table.
SELECTing Data trough a View works fine.
But when I want to INSERT, UPDATE or DELETE data through a view, SQL Server says that there are missing permissions on the base table.
Following objects:
Table, named: dbo.test
View, named: dbo.vw_test
The table has two columns:
Column_1 IDENTITY....
Column_2 int (updateable column)
The view has following statement:
SELECT * FROM dbo.test;
I have created a LOGIN and a USER on this database with SELECT, INSERT, UPDATE, DELETE permissions on this view. There is no DENY on the base table.
As said, SELECT works, but updating Column_2 not.
Why? Do I need to grant all rights to the base table?
I hopefully think not. I already have created an INSTEAD OF INSERT trigger on the view to test it. But it doesn't work.
What can I do, to modify data trough a view?
I guess that you've misunderstood views. If you are modifying data inside a view it means that you are directly accessing all tables that exist into the SQL statement defining that View. This means that if you want to modify data, modifications will be done directly to all tables that are represented by that view, which at the end means that you have to give enough permissions in order to be able to perform those kind of actions. Please see the reference in this link (section Before you begin -> permissions).
Using a view to encapsulate a table whose name changes yearly (tablename_year) called "vw_Tablename_Current" so I don't have to change any procs that use the table to reflect the new table name, just the view.
This is temporary until I'm able to make deeper model changes. Is there any performance hit on wrapping a single table in a view like this?
Sql Server 2005
You can use a synonym as well which is cleaner
CREATE SYNONYM tablename FOR tablename_year;
No, there is no performance difference if the view is essentially a SELECT * FROM table