I have an existing view I need materialized. Ideally, I would drop the view and create a materialized one, but dropping the view would require a cascade drop and that would create a lot more work.
Is there an expression to change the view to a materialized one?
Related
I am trying to understand but its not obvious to me in the documentation of Azure SQL DW, if you materialize a view and any of the base tables of the view is being updated with data or data is deleted / truncated, will this affect what is accessible in the materialized view or will what was created in the materialized view at execution persist?
A Materialized View persists the data returned from the view definition query and automatically gets updated as data changes in the underlying tables.
I tried All the operation you mentioned in Question on the base table of materialized view It is updating the view according to the changes perform on base table materialized view without restrictions.
Sample data
Created Materialized view on table
Updated data in base table and performed select operation on view
Deleted data from base table and performed select operation on view
Inserted data in base table and performed select operation on view
After every update on base table Materialized view is getting updated automatically.
If I have a fulltext index on a field, say "First Name + Last Name" and I create the following materialized view:
CREATE MATERIALIZED VIEW names AS SELECT * FROM table
Am I able to use the fulltext index when querying the materialized view, or is it necessary that a FTS index is rebuilt if I'm to run a query that searches against that MV?
Think of a materialized view as its own table, which is populated when the view is created or refreshed. When the materialized view is being populated, it will use whatever indexes are on the source tables which are relevant. However, when you query the materialized view, you're not interacting with any of those source tables, and so none of those indexes can come into play.
If you want to do fulltext queries or the like on a materialized view, you'll want to create a relevant index on the materialized view itself.
I need to create an index on a view in mariaDB. Is this possible?
Note that, I can't create an index on tables since admininstrator permissions are not given to access tables.
No, you cannot create indexes on a View in MariaDB.
Indeed, Views are not real relations, but simply aliases on relations (tables).
You could have created indexes on a Materialized View but MariaDB does not implement (in a native way) Materialized Views as of today.
I've got a question about script in Oracle!
I have a materialized view on a prebuilt table, in my BBDD, (this MV is of the user DAT_OWN, other 2 user (APP & BO) have synonym on this MV)
I have to change the MV and add a column. I know that I need to drop this MV and create a another one, but what's append with the synonym?
I have a previous script like:
DROP SYNONYM APP.STAT_VOZ;
CREATE SYNONYM APP.STAT_VOZ FOR DAT_OWN.STAT_VOZ;
DROP SYNONYM BO.STAT_VOZ;
CREATE SYNONYM BO.STAT_VOZ FOR DAT_OWN.STAT_VOZ;
DROP MATERIALIZED VIEW DAT_OWN.STAT_VOZ;
CREATE MATERIALIZED VIEW DAT_OWN.STAT_VOZ
ON PREBUILT TABLE WITH REDUCED PRECISION
REFRESH COMPLETE
START WITH TO_DATE('21-ene-2013 19:20:00','dd-mon-yyyy hh24:mi:ss')
NEXT (trunc(SYSDATE,'HH')+19/72)
WITH PRIMARY KEY
AS
SELECT TO_CHAR (SUM (COUNT)) AS sum_count,
start_date AS date_hour,
input_type AS input_type
FROM DAT_OWN.another_table
WHERE start_date > TO_CHAR (SYSDATE - 60, 'yyyymmdd')
GROUP BY start_date
Why would somebody do a drop synonym APP and create synonym APP drop synonym BO and create synonym BO BEFORE dropping of the materialized View? In my opinion, I have to do
drop synonym1
drop synonym2
drop Mview
create Mview
create Synonym1
Create Synonym2
I'm sure that the programmer before me did a good job, but I can't understand why they did it that way! Can somebody explain me this, please?
Regards
Your original script was probably just written by an "old school" developer. Most people are accustomed to dropping objects immediately before recreating them. As you've noticed, the sequence is not important.
Most people these days use CREATE OR REPLACE syntax instead of first dropping the object. Here is a good explanation of that concept.
There is probably no need to touch either synonym in the script.
A synonym is just a pointer. There is no requirement that the object pointed to by the synonym exists at all. If you simply drop and re-create the materialized view, the synonyms will automatically point at the newly created materialized view. Of course, after the materialized view is dropped and before it is recreated, if a session tries to use the synonym to query the materialized view, that session will get an error that the object doesn't exist. But, presumably, you're waiting to drop and recreate the materialized view until no one will be using it so that generally isn't a major concern.
I create a indexed view View1 on Table1 and Table2 and have instead of trigger and after trigger on Table1 that use of View1. It seem that data of View1 not change when I use this view on instead of trigger and after trigger. But I want to use View1 with new data when use this view on after trigger. How can I do it. It should be noted that I use with Noexpand hint when use indexed view (when don't use with noexpand hint in SQL Server 2008 R2 act this indexed view such as no indexed view).
The indexed view is updated after all triggers on the base tables are executed. You can see that in the query plan. There will be only one clustered index update on the view.
However, you can create INSTEAD OF triggers on the view and then make all your operations on the indexed view. However,there are some restrictions when updating/inserting/deleting through an updateable view. You can read about them here.
Note that views allow only INSTEAD OF triggers, not AFTER too.
The most important thing to know about updating indexed views is that any modifications, including UPDATE, INSERT, and DELETE statements, must reference columns from only one base table.