SQL Views

SQL Views

A SQL view is a virtual table that is created from a query using one or more base tables or views. A view can be used to simplify complex queries, provide data security, or present data in different ways. A view does not store any data itself, but only references the data in the underlying tables or views.

To create a view, you use the CREATE VIEW statement with the following syntax:

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

The view_name is the name of the view that you want to create. The SELECT statement defines what columns and rows will be included in the view. You can use any valid SQL query as the SELECT statement for a view.

To query data from a view, you use the same syntax as querying data from a table:

SELECT column1, column2, ...
FROM view_name
WHERE condition;

You can also update, insert, or delete data from a view, as long as the view is updatable. A view is updatable if it meets certain criteria, such as having a one-to-one relationship with the base table, not containing any aggregate functions, and not using any DISTINCT or GROUP BY clauses.

To modify the definition of a view, you use the ALTER VIEW statement with the following syntax:

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

The ALTER VIEW statement replaces the existing definition of the view with the new one.

To delete a view, you use the DROP VIEW statement with the following syntax:

DROP VIEW view_name;

The DROP VIEW statement removes the view from the database.

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