Usage of view in sql

A View in SQL is a virtual table that derives data from an existing table or query. It does not store actual data but calculates data from underlying tables or queries as needed. Advantages of View include: Data abstraction Data safety Performance optimization Data consistency To create a View, use the CREATE VIEW statement, specifying the View name and selecting columns from the underlying table or query. Once created, a View can be used like a normal table for selecting data, but there are restrictions on inserting, updating, or deleting data. Understanding the benefits, syntax, and usage of Views is critical to managing data effectively.

Usage of View in SQL

What is View?

View is a feature in SQL that allows you to create virtual tables that derive data from existing tables or queries. Unlike a normal table, a View does not store actual data but instead calculates data from the underlying table or query as needed.

Advantages of View

• Data abstraction. View allows you to create simplified views of your data that hide underlying table structures and complex queries.
• Data security. View can be used to restrict access to sensitive data, allowing only necessary columns and rows to be viewed.
• Performance optimization. View can cache query results, thereby improving the performance of common queries.
• Data consistency. View always reflects the latest data in the underlying table, ensuring data consistency.

How to create a View

To create a View, use the following syntax:

<code class="sql">CREATE VIEW [view_name] AS
[SELECT statement]</code>

For example, the following query creates a view named ## View of #employee_summary, which displays the employee's name, department and salary:

<code class="sql">CREATE VIEW employee_summary AS
SELECT name, department, salary
FROM employees;</code>

After creating the View using View

• Select data: Use the SELECT statement to select data from the View.
• Insert data: View cannot be used to insert data.
• Update data: In some cases, View can be used to update data.
• Delete data: View cannot be used to delete data.

Notes

• Dependencies. View relies on the underlying table or query. If the underlying data changes, the data in the View will also change.
• maintain. After creating Views, you need to maintain them regularly to ensure they are up to date.
• Performance impact. Complex views may impact performance because they require data to be calculated in real time.

Conclusion

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