This restriction applies to all columns in views that contain aggregate values—that is, views whose definition includes a group by or compute clause. Here is a view defined with a group by clause and the rows seen through it:
create view categories (category, average_price) as select type, avg(price) from titles group by type
select * from categories
category average_price ------------- ------------- UNDECIDED NULL business 13.73 mod_cook 11.49 popular_comp 21.48 psychology 13.50 trad_cook 15.96 (6 rows affected)
It does not make sense to insert rows into the view categories. To what group of underlying rows would an inserted row belong? Updates on the average_price column are not allowed because there is no way to know from any value you might enter there how the underlying prices should be changed.
