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{ “title”: “View”, “language”: “en” }

View

Views (logical views) are stored queries that encapsulate one or multiple SELECT statements. Views dynamically access and compute database data when executed. Views are read-only and can reference any combination of tables and other views.

Views can be used for the following purposes:

• To simplify access or provide secure access by hiding complex SELECT statements from users. For example, you can create a view that displays only the data users need from various tables while hiding sensitive data in those tables.
• To encapsulate details of table structures that may change over time behind a consistent user interface.

Unlike materialized views, logical views are not materialized, which means they do not store data on disk. Therefore, they have the following limitations:

• When the underlying table data changes, Doris does not need to refresh the view data. However, accessing and computing data through views can incur some overhead.
• Views do not support insert, delete, or update operations.

Creating View

The syntax for creating a logical view is as follows:

CREATE VIEW [IF NOT EXISTS]
 [db_name.]view_name
 (column1[ COMMENT "col comment"][, column2, ...])
AS query_stmt

Explanation:

• Views are logical and have no physical storage. All queries on views are equivalent to queries on the corresponding subquery of the view.
• query_stmt is any supported SQL statement.

Example:

• Creating a view named example_view in the example_db database:

CREATE VIEW example_db.example_view (k1, k2, k3, v1)
AS
SELECT c1 as k1, k2, k3, SUM(v1) FROM example_table
WHERE k1 = 20160112 GROUP BY k1,k2,k3;

• Creating a view with comments:

CREATE VIEW example_db.example_view
(
    k1 COMMENT "first key",
    k2 COMMENT "second key",
    k3 COMMENT "third key",
    v1 COMMENT "first value"
)
COMMENT "my first view"
AS
SELECT c1 as k1, k2, k3, SUM(v1) FROM example_table
WHERE k1 = 20160112 GROUP BY k1,k2,k3;