Detailed explanation of Oracle views.

1 year ago
Isabella Edwards
2 minutes

An Oracle view is a virtual table created from the result of one or more tables or views. Views do not actually store data, but instead dynamically generate data based on the rules defined in the query from base tables or other views.

Views offer several key advantages:

  1. Simplify data access: Views can hide the complexity and structural details of base tables by providing a simple interface for users to easily access and manipulate data.
  2. Data security: By using views, access to specific data can be restricted for users. Views can be utilized to filter sensitive information, only showing users the data they are authorized to see.
  3. Logical data independence: By using views, the physical storage structure of data can be separated from logical data access. Thus, when the structure of the base table changes, only the corresponding view definition needs to be modified, rather than having to modify the applications that depend on that view.
  4. Performance optimization: Views can pre-calculate and store complex query results to improve query performance. Additionally, materialized views can be used to cache pre-calculated results, further enhancing query performance.

The syntax for creating a view is as follows:

CREATE [OR REPLACE] VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
[WHERE condition];

In this case, view_name is the name of the view, column1, column2, … are the column names of the view, table_name is the name of the base table, and condition is the query condition.

Views can be used and queried just like regular tables. For example:

SELECT * FROM view_name;

It is important to note that views are not standalone objects; they depend on the existence and structure of the base tables. If the base table is deleted or its structure is altered, the related views will also be affected. Therefore, when designing views, it is important to consider the stability and consistency of the base table.

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