Question: Do database views affect performance?

Answer

Yes, database views can affect performance both positively and negatively, depending on how they're used.

On one hand, views can improve performance. They allow for simplification of complex queries by abstracting join operations or subqueries into a single reusable object - the view itself. This way, instead of running a complicated and costly query multiple times, you can run it once, store it as a view, and then access that view just like you'd access a table.

Here is an example on how to create a view in SQL:

CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;

On the other hand, views can negatively impact performance. If your view is built on top of many complex queries, involving large data sets or multiple joins, every time you call the view, these underlying queries also need to be executed, which can lead to slower performance. In such cases, materialized views (which store the result set of the query upon which they are based) might be a better choice, but they come with their own trade-offs such as storage cost and keeping them updated when base data changes.

Another potential downside is that, depending on the DBMS and the complexity of the view, the query optimizer might not be able to choose the most efficient execution plan for queries involving views, leading to sub-optimal performance.

In conclusion, while views offer convenience and can sometimes boost performance, they should be used judiciously, taking into account the specific requirements of your system and the characteristics of your data.