Views are lightweight logical constructs that act as aliases for queries. You can
specify a view name in a query (a
SELECT statement or the
SELECT portion of an
INSERT statement) where you would
usually specify a table name.
A view lets you to:
- Issue complicated reporting queries with compact and simple syntax:
- Reduce maintenance by avoiding the duplication of complicated
queries across multiple applications in multiple languages:
CREATE VIEW v2 AS SELECT t1.c1, t1.c2, t2.c3 FROM t1 JOIN t2 ON (t1.id = t2.id); -- This simple query is safer to embed in reporting applications than the longer query above. -- The view definition can remain stable even if the structure of the underlying tables changes. SELECT c1, c2, c3 FROM v2;
- Build a new, more refined query on top of the original query by adding new clauses, select-list expressions, function calls, and so on: This technique lets you build up several more or less granular variations of the same query, and switch between them when appropriate.
- Set up aliases with intuitive names for tables, columns and result sets from joins.
- Avoid coding lengthy subqueries and repeating the same subquery text in many other queries.
To create, alter, or drop views, use the
ALTER VIEW, and the
You cannot insert into views.
To see the definition of a view, issue a
FORMATTED statement, which shows the query from the original
CREATE VIEW statement