In this article, we will dive into the world of SQL Server views and explore some advanced features that can enhance your database management experience.
Simple Views
Let’s start with the basics. Views in SQL Server are virtual tables that are based on the result of a query. They allow you to simplify complex queries and provide a convenient way to access and manipulate data.
Creating a simple view is straightforward:
CREATE VIEW jk_v_View1
AS
SELECT * FROM jk_t_source1
You can then use the view just like you would use a table:
SELECT * FROM jk_v_View1
However, it’s important to note that you cannot use an ‘ORDER BY’ clause in a view. If you try to do so, you will receive an error message. To work around this limitation, you can use the ‘TOP’ keyword:
CREATE VIEW jk_v_View1
AS
SELECT TOP 100 PERCENT * FROM jk_t_source1
ORDER BY f4
Customizing Views
Views offer flexibility in terms of column names and data types. You can specify different column names in the view compared to the underlying table:
CREATE VIEW jk_v_View1(fa, fb, fc, fd)
AS
SELECT * FROM jk_t_Source1
You can also select a subset of columns or use computed columns:
CREATE VIEW jk_v_View1(fa, fc, fd)
AS
SELECT f1, f3, f4 FROM jk_t_Source1
CREATE VIEW jk_v_View1(fa1, fb1, fa2, fb2)
AS
SELECT f1, f2, f1, f2 FROM jk_t_Source1
CREATE VIEW jk_v_View1(f1)
AS
SELECT f1 + 10 FROM jk_t_Source1
Furthermore, you can modify the data types of columns in the view:
CREATE VIEW jk_v_View1
AS
SELECT f1, f2, f3, CAST(f4 AS varchar(19)) AS f4 FROM jk_t_Source1
Schemabinding
Schemabinding is a feature that ensures the integrity and stability of views by binding them to the underlying schema. It helps to avoid dependency issues when modifying objects that are referenced by views.
For example, if you drop a function that is used by a view, you will receive an error. To overcome this, you can use the SCHEMABINDING option when creating the view:
CREATE VIEW jk_v_View1 WITH SCHEMABINDING
AS
SELECT f1, f2, f3, f4 FROM dbo.jk_f_funcNonScalar()
However, it’s important to note that when using SCHEMABINDING, you cannot use the “*” in select statements within the view.
Indexed Views
Indexed views are a powerful feature in SQL Server that allow you to create indexes on views, improving query performance. However, there are certain restrictions and considerations when working with indexed views.
The first index you create on a view must be a unique clustered index. Additionally, the view cannot contain any nondeterministic expressions. If these conditions are not met, you will receive an error when trying to create an index on the view.
It’s important to note that maintaining indexed views can be complex and may not always provide a significant performance improvement. It’s recommended to carefully evaluate the benefits and drawbacks before implementing indexed views in your database.
Partitioned Views
Partitioned views allow you to horizontally partition a table into multiple tables based on specific criteria. This can improve performance and load balancing in scenarios where only a subset of the data is frequently accessed.
To create a partitioned view, you can use the UNION ALL operator to combine multiple tables:
CREATE VIEW jk_v_horizpart
AS
SELECT * FROM jk_horiz_1
UNION ALL
SELECT * FROM jk_horiz_2
UNION ALL
SELECT * FROM jk_horiz_3
You can then query the partitioned view, and SQL Server will optimize the query execution based on the check constraints and the WHERE clause.
It’s worth mentioning that you can also distribute partitioned views across multiple physical servers for further load balancing and performance optimization.
Conclusion
Views are a powerful tool in SQL Server that can simplify complex queries and provide flexibility in data access and manipulation. By understanding advanced features like schemabinding, indexed views, and partitioned views, you can optimize your database design and improve query performance.
Thank you for reading!