An updatable view is a special case of a deletable view. A deletable view becomes an updatable view when at least one of its columns is updatable.
A column of a view is updatable when all of the following rules are true:
- The view is deletable.
- The column resolves to a column of a table (not using a dereference operation) and the READ ONLY option is not specified.
- All the corresponding columns of the operands of a UNION ALL have exactly matching data types (including length or precision and scale) and matching default values if the fullselect of the view includes a UNION ALL.
The following example uses constant values that cannot be updated. However, the view is a deletable view and at least one of its columns is updatable. Therefore, it is an updatable view.
CREATE VIEW updatable_view (number, current_date, current_time, temperature) AS SELECT number, CURRENT DATE, CURRENT TIME, temperature) FROM weather.forecast WHERE number = 300