PL/SQL learning notes-View

1. create or modify an attempt

Create or replace view v_xland asselect title, content from labor. xland;

Ii. delete a view

Drop view v_xland;

3. Update the data in the view.
If there is no limit to retrieving data in a view
If you want to update, delete, and create data for a view, the view must meet the following conditions:
1. The view cannot contain the keyword or clause of Union distinct group by order.
2. subqueries are not allowed in the view.
3. The view cannot contain grouping functions.
4. columns to be updated are not defined by column expressions.
5. All not null columns in the table are in the view.

4. Constraints and primary keys in the view
1: data that does not conform to the constraints of a column in the view will not appear in the view.
2: The primary key in the base table appears in the view and will become the primary key of the view.