| 8. 1. 2. Creating and Using a View |
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You create a view using CREATE VIEW , which has the following simplified syntax: |
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CREATE [OR REPLACE] VIEW [{FORCE | NOFORCE}] VIEW view_name
[(alias_name[, alias_name...])] AS subquery
[WITH {CHECK OPTION | READ ONLY} CONSTRAINT constraint_name];
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where |
- OR REPLACE specifies the view is to replace an existing view if present.
- FORCE specifies the view is to be created even if the base tables don't exist.
- NOFORCE specifies the view is not to be created if the base tables don't exist; NOFORCE is the default.
- alias_name specifies the name of an alias for an expression in the subquery.
- There must be the same number of aliases as there are expressions in the subquery.
- subquery specifies the subquery that retrieves from the base tables.
- If you've supplied aliases, you can use those aliases in the list after the SELECT clause.
- WITH CHECK OPTION specifies that only the rows that would be retrieved by the subquery can be inserted, updated, or deleted.
- By default, rows are not checked that they are retrievable by the subquery before they are inserted, updated, or deleted.
- constraint_name specifies the name of the WITH CHECK OPTION or READ ONLY constraint.
- WITH READ ONLY specifies that rows may only read from the base tables.
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There are two basic types of views: |
Simple views, which contain a subquery that retrieves from one base table |
Complex views, which contain a subquery that: |
- Retrieves from multiple base tables
- Groups rows using a GROUP BY or DISTINCT clause
- Contains a function call
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Quote from: |
Oracle Database 10g SQL (Osborne ORACLE Press Series) (Paperback) |
# Paperback: 608 pages |
# Publisher: McGraw-Hill Osborne Media; 1st edition (February 20, 2004) |
# Language: English |
# ISBN-10: 0072229810 |
# ISBN-13: 978-0072229813 |