What are views in SQL?
What are views in SQL?
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.
What is indexed view in SQL?
An indexed view has a unique clustered index. The unique clustered index is stored in SQL Server and updated like any other clustered index. An indexed view is more significant compared to standard views that involve complex processing of large numbers of rows, such as aggregating lots of data, or joining many rows.
How do I create an updatable view in SQL Server?
However, to create an updatable view, the SELECT statement that defines the view must not contain any of the following elements:
- Aggregate functions such as MIN, MAX, SUM, AVG, and COUNT.
- GROUP BY clause.
- HAVING clause.
- UNION or UNION ALL clause.
- Left join or outer join.
What is INFORMATION_SCHEMA in SQL?
INFORMATION_SCHEMA provides access to database metadata, information about the MySQL server such as the name of a database or table, the data type of a column, or access privileges. Other terms that are sometimes used for this information are data dictionary and system catalog.
Why views are used in SQL?
Views are used for security purposes because they provide encapsulation of the name of the table. Data is in the virtual table, not stored permanently. Views display only selected data. We can also use Sql Join s in the Select statement in deriving the data for the view.
What is materialized view in SQL?
A materialized view is a database object that contains the results of a query. The FROM clause of the query can name tables, views, and other materialized views. Collectively these objects are called master tables (a replication term) or detail tables (a data warehousing term).
What are updatable views?
An updatable view is a special case of a deletable view. A deletable view becomes an updatable view when at least one of its columns is updatable. A column of a view is updatable when all of the following rules are true: The view is deletable.
What is metadata in SQL?
Metadata in simple words describe as data about data. Usually, the metadata returns the information about the database, db objects, db files, etc., in the SQL server.
Can I delete INFORMATION_SCHEMA?
You also cannot delete the information_schema database.
What are the four different types of view?
There are total four types of views, based on the way in which the view is implemented and the methods that are permitted for accessing the view data. They are – Database Views, Projection Views, Maintenance Views, and Helps Views,.