What does view mean in sql

The view in SQL is a virtual table that is generated by querying the base table and does not actually store data. It provides the advantages of data abstraction, security control, performance optimization, and logical organization. Views are created through the CREATE VIEW statement, and operations such as query, update, and delete can be used, but updates to the view will affect its base table. The main differences between views and tables are data storage (virtual vs. real), performance (views are generally faster), update impact (views affect base tables, tables do not), and flexibility (views can change queries at any time, while table schema difficult to change).

The meaning of view in SQL

view (view) is a virtual table in SQL, which passes SQL statements are generated by querying the base table and do not actually store data. Views provide a mechanism for viewing and manipulating data from different perspectives.

Advantages of view:

• Data abstraction: view hides the underlying structure of the data and simplifies queries.
• Security: View can restrict access to data, allowing users to view only specific columns or rows.
• Performance Optimization: By creating views, complex queries can be pre-calculated and stored, thereby improving the performance of subsequent queries.
• Logical organization: view can organize data according to different logics to facilitate query and management.

Creation of view:

<code class="sql">CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;</code>

Usage of view:

view can be used like a normal table, You can query, update, delete and other operations on it. However, updates to the view affect its base tables.

The difference between view and table:

##SafetyCan limit the data AccessSecurity is determined by the permissions of the underlying tableFlexibilityYou can change the querytable at any time as needed Once the schema is created it cannot be easily changed

Features	view	Table
Data storage	Virtual, does not store data	Actual, stores data
Performance	Usually faster than the table because it pre-calculates the data	Usually slower than the view because it needs to calculate the data in real time
Update	Updating the view will affect its base table	Updating the table will not affect other tables

The above is the detailed content of What does view mean in sql. For more information, please follow other related articles on the PHP Chinese website!