Updating data in a view sql
This makes views useful for abstracting or hiding complex queries.The following picture illustrates a view that includes columns from multiple tables: Generally speaking, views provide the following advantages: You can restrict users to access directly to a table and allow them to access a subset of data via views.A view is updatable if the statement against the view can be translated into the corresponding statement against the underlying table.Let’s consider the following database tables: In database diagram, a car belongs to one brand while a brand has one or many cars.
You can determine if the current user has %ALTER privilege by invoking the %CHECKPRIV command. You can use the The following examples create a view then alter that view.
In some databases, such as Postgre SQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table.
When using FROM, one should ensure that the join produces at most one output row for each row to be modified.
You can determine if a specified user has %ALTER privilege by invoking the $SYSTEM. Programs are provided to query the view and to delete the view.
Note that altering the view replaces the column list with a new column list; it does not preserve the prior column list.