Table-valued functions are a powerful feature in SQL Server that allow you to return tabular result sets, similar to views. In this blog post, we will explore the concept of table-valued functions and how they can be implemented and used in your SQL Server database.

Creating and Implementing Table-Valued Functions

The body of a table-valued function contains a query that defines the result set. Let’s take a look at an example:

CREATE FUNCTION GetAllProducts( )
RETURNS TABLE
AS
RETURN
(SELECT ProductID, ProductName, RetailPrice, Category
FROM CurrentProducts)
GO

In this example, the table-valued function “GetAllProducts” is created, which returns all the records from the “CurrentProducts” table. The “RETURNS TABLE” keyword specifies that the function will return the result in the form of a table.

To query a table-valued function, you can use a SELECT statement similar to querying a table or a view:

SELECT * FROM GetAllProducts()

Views versus Parameterized Table-Valued Functions

Views and table-valued functions both provide a way to see the result set of a pre-defined query. However, there are some differences between them. Views are hard-coded and their criteria cannot be changed, while table-valued functions can display different results by passing values into their parameters at runtime.

Let’s consider an example where we want to retrieve records from the “CurrentProducts” table based on a specific category:

CREATE FUNCTION GetCategoryProducts(@Category VARCHAR(50))
RETURNS TABLE
AS
RETURN
(SELECT ProductID, ProductName, RetailPrice, Category
FROM CurrentProducts
WHERE Category = @Category)

In this example, the table-valued function “GetCategoryProducts” takes a parameter “@Category” and returns the records that match the specified category. You can call this function with different category values to retrieve different results:

SELECT * FROM GetCategoryProducts('Medium-stay')

It’s important to remember to include the required parameters when calling a table-valued function. Forgetting to include a parameter will result in an error message.

Conclusion

Table-valued functions are a useful feature in SQL Server that allow you to return tabular result sets based on underlying queries. They provide flexibility by allowing you to pass parameters and retrieve different results based on those parameters. By understanding and utilizing table-valued functions, you can enhance the functionality and efficiency of your SQL Server database.

Thank you for reading this blog post about table-valued functions. If you have any questions or comments, please leave them below.