A view is a virtual table.
This chapter shows how to create, update, and delete a view.
In SQL, a view is a virtual table based on the result-set of an SQL statement.
A view contains rows and columns, just like a real table. The fields in a view are fields from
one or more real tables in the database.
You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the
data were coming from one single table.
Note: A view always shows up-to-date data! The database engine recreates the data, using
the view's SQL statement, every time a user queries a view.
If you have the Northwind database you can see that it has several views installed by
The view "Current Product List" lists all active products (products that are not
discontinued) from the "Products" table. The view is created with the following
We can query the view above as follows:
Another view in the Northwind sample database selects every product in the "Products"
table with a unit price higher than the average unit price:
Another view in the Northwind database calculates the total sale for each category in 2015. Note
that this view selects its data from another view called "Product Sales for 2015":
We can also add a condition to the query. Now we want to see the total sale only for the category
You can update a view by using the following syntax:
Now we want to add the "Category" column to the "Current Product List" view.
We will update the view with the following SQL:
You can delete a view with the DROP VIEW command.
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