Database management is an essential aspect of any organization that deals with a significant amount of data. Views and Materialized views are important elements of any database management system. However, it is a common misconception that both terms are interchangeable.
Understanding Views and Materialized Views
A view is a virtual table that contains a specific subset of data from one or more tables. It does not store any data on its own but serves as a layer between the application and the database. Views are used to simplify complex queries, provide access control, and present data in a meaningful manner to the end-user. Views are dynamic, which means they are updated in real-time whenever there is a change in the underlying data.
The following snippet is an example of how to create a view.
CREATE VIEW employee_view AS
SELECT first_name, last_name, department_id
FROM employees
WHERE salary > 50000;
Materialized views, on the other hand, are physical copies of the query result stored in the database. It is a precomputed table that contains the results of a query. Materialized views are often used to improve query performance by reducing the amount of time required to compute a complex query. Unlike views, materialized views are not dynamic, and the data is refreshed periodically or manually.
Materialized views are created as such.
CREATE MATERIALIZED VIEW employee_materialized_view AS
SELECT first_name, last_name, department_id
FROM employees
WHERE salary > 50000;
Once created, materialized views need to be refreshed so that they contain the latest copy of the data. The following statement will rerun the query used to create the materialized view and update it.
REFRESH MATERIALIZED VIEW employee_materialized_view;
When to Use Views and Materialized Views in Your Database
Views are ideal for scenarios where you need to simplify complex queries or provide access control to specific data. Views are also useful when you need to present data in a meaningful manner to the end-user. Materialized views, on the other hand, are ideal for scenarios where you have a complex query that takes a long time to compute. By creating a materialized view, you can reduce the time required to compute the query. Materialized views are also useful when you need to perform complex aggregations or calculations on a large dataset.
In summary, views and materialized views are two important elements of any database management system. While both serve the same purpose of simplifying complex queries, they differ in the way they store data and the scenarios in which they are ideal. It is important to understand the differences between views and materialized views to determine which one is best suited for your database needs.