Provides information about using Views as lightweight logical constructs that can act as aliases for queries. Using a view, you can issue complicated reporting queries with compact and simple syntax and reduce maintenance by avoiding the duplication of complicated queries across multiple applications in multiple languages.
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.
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;
A view lets you to:
- 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
CREATE VIEW, the
VIEW, and the
DROP VIEW statements respectively.
You cannot insert into views.
To see the definition of a view, issue a
DESCRIBE FORMATTED statement,
which shows the query from the original
CREATE VIEW statement