Inline Table-Valued Functions (TVFs)

 Inline Table-Valued Functions (TVFs) in SQL Server are a type of user-defined function that returns a result set (table) and can be used similarly to a table or view in queries. Unlike multi-statement table-valued functions, inline TVFs have a simpler syntax and are more efficient in terms of performance because they are essentially views with parameters.

Key Characteristics of Inline TVFs

1. Single SELECT Statement: An inline TVF contains a single SELECT statement that defines the table structure and the data returned.

2. Parameterization: Inline TVFs can accept parameters, which allows for dynamic querying based on input values.

3. Performance: Inline TVFs often perform better than multi-statement TVFs because they are optimized as views by the query processor, and there is no intermediate storage of results.

4. Schema Binding: Inline TVFs can use WITH SCHEMABINDING to bind the function to the schema of the underlying tables, preventing modifications that would affect the function.

Syntax for Creating an Inline Table-Valued Function

Here’s the basic syntax for creating an inline TVF:

CREATE FUNCTION dbo.GetSalesByDateRange
(
    @StartDate DATE,
    @EndDate DATE
)
RETURNS TABLE
AS
RETURN
(
    SELECT 
        SalesID,
        SalesPersonID,
        SalesAmount,
        SalesDate
    FROM 
        dbo.Sales
    WHERE 
        SalesDate BETWEEN @StartDate AND @EndDate
);

Using Inline TVFs

Once created, you can query an inline TVF just like a regular table or view:

SELECT 
    SalesPersonID,
    SUM(SalesAmount) AS TotalSales
FROM 
    dbo.GetSalesByDateRange('2024-01-01', '2024-12-31')
GROUP BY 
    SalesPersonID;

Key Points

• Efficiency: Inline TVFs are generally more efficient than multi-statement TVFs because they are expanded into the calling query’s execution plan, reducing overhead.

• Index Usage: Inline TVFs can leverage indexes on the underlying tables because they are essentially a single query.

• Use Cases: They are useful for encapsulating reusable queries that need to be parameterized and can simplify complex query logic.

Example Scenario

Consider a sales database where you frequently need to analyze sales data for specific date ranges. By creating an inline TVF, you can encapsulate the logic for filtering the sales data based on the date range and use it in various queries, improving maintainability and readability.

Overall, inline table-valued functions provide a powerful and efficient way to handle parameterized queries and encapsulate complex query logic in SQL Server.