<|im_start|>system
You are a helpful AI assistant.<|im_end|>
<|im_start|>user
What is VIEW in SQL?<|im_end|>
<|im_start|>assistant
A view is a virtual table containing the result of a query. Views let you reuse parts of a query and organize your code better. An example view looks like this:

```sql
CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = 'Brazil';
```
This query selects all customers from Brazil and stores them into the view `[Brazil Customers]`. Views can be queried like real tables:

```sql
SELECT * FROM [Brazil Customers] ORDER BY CustomerName LIMIT 5;
```
This query returns the first 5 rows in the view, ordered by the customer name.
You can also update views:
```sql
CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = 'Brazil';
```
or delete them.
```sql
DROP VIEW [Brazil Customers];
```<|im_end|>
<|im_start|>user
Thank you for your reply.

Please modify the code to select from an array of datasets 5 x 5.<|im_end|>
<|im_start|>assistant
I'm sorry, but views are not designed to select data from an array of datasets. Views are a database object that represents a stored query, which allows you to reuse parts of a query and organize your code better, as I mentioned in my previous response.

If you have an array of datasets and you want to select 5 x 5 data from them, you would need to use a different approach, such as using a programming language or a database query to extract the data you need.

If you provide more information about the datasets you have and what you are trying to achieve, I can try to provide more specific guidance.<|im_end|>
<|im_start|>user
Where would I need to store the actual data for VIEW to use?<|im_end|>
<|im_start|>assistant
The actual data is stored in the original tables that were part of the query of the _VIEW_ creation. In the example above, that would be the `Employees` table. Imagine the _VIEW_ as a query saved for later use. In essence, that's just a convenience for the user, as the query to the _VIEW_ could be understood far easier than the original query.

However, the above isn't true for _MATERIALIZED VIEW_. Those are specialized versions of a _VIEW_, which cache the data from the creation query. 

```SQL
CREATE MATERIALIZED VIEW Employee_Summary_M AS
SELECT first_name, last_name, salary
FROM Employees;
```

In that case, the data is stored in two places. The original, actual data in the original tables (in our case `Employee` table). The interim, cached data is stored in the _MATERIALIZED VIEW_, until it gets invalidated. In PostgreSQL, you can invalidate that cache with _REFRESH MATERIALIZED VIEW_ query. Other databases have some variations on the functionality of the _MATERIALIZED VIEW_.

```SQL
REFRESH MATERIALIZED VIEW Employee_Summary_M;
```<|im_end|>