This restriction applies to all columns in views that contain aggregate values—that is, views that have a definition that 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)
You cannot insert rows into the view categories, because the group to which an inserted row would belong cannot be determined. Updates on the average_price column are not allowed, because there is no way to determine how the underlying prices should be changed.
