If you define a view with an outer join, and then query the view with a qualification on a column from the inner table of the outer join, the query behaves as though the qualification were part of the WHERE clause of the view, not part of the ON clause of the outer join in the view. Thus the qualification operates only on rows AFTER the outer join is complete. For example, the qualification operates on NULL extended rows if the outer join condition is met, and eliminates rows accordingly.
The following rules determine what types of updates you can make to columns through join views:
delete statements are not allowed on join views.
insert statements are not allowed on join views created with check option.
update statements are allowed on join views with check option. The update fails if any of the affected columns appears in the where clause, in an expression that includes columns from more than one table.
If you insert or update a row through a join view, all affected columns must belong to the same base table.
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