User Defined Inline Table-Valued Functions with CROSS APPLY | Microsoft Fabric Tutorial

In this Microsoft Fabric tutorial, we’ll demonstrate how to create and use inline table-valued functions (iTVFs) and apply them with CROSS APPLY. These are great tools for reusable logic and dynamic row-by-row evaluation.

🧠 What is a Function in SQL?

A function is a reusable SQL object that returns either a value or a table. In Fabric Warehouse, only inline table-valued functions (iTVFs) are currently supported.

🚫 Not Supported:

• Scalar functions
• Multi-statement table-valued functions

✅ Supported:

• Inline Table-Valued Functions (iTVFs)

🏗️ Step 1: Create Sample Orders Table

CREATE TABLE dbo.Orders (
    OrderID INT,
    CustomerName VARCHAR(100),
    OrderDate DATE,
    OrderAmount DECIMAL(10, 2)
);

💾 Step 2: Insert Sample Data

INSERT INTO dbo.Orders VALUES
(1, 'Aamir', '2024-01-10', 1200.00),
(2, 'Sara', '2024-02-15', 800.00),
(3, 'John', '2024-03-20', 300.00),
(4, 'Mia', '2024-03-22', 1500.00),
(5, 'Aamir', '2024-04-01', 200.00);

🔄 Step 3: Create Discount Function with CROSS APPLY

This iTVF applies a 10% discount to a given amount:

CREATE FUNCTION dbo.fn_ApplyDiscount (@Amount DECIMAL(10,2))
RETURNS TABLE
AS
RETURN (
    SELECT @Amount * 0.90 AS DiscountedAmount
);

✅ Using CROSS APPLY

SELECT 
    o.OrderID, o.CustomerName, o.OrderAmount,
    d.DiscountedAmount
FROM dbo.Orders o
CROSS APPLY dbo.fn_ApplyDiscount(o.OrderAmount) d;

🔸 Step 4: Create Function to Filter Orders

This function returns orders where the amount is greater than or equal to a specified value:

CREATE FUNCTION dbo.fn_GetHighValueOrders (@MinAmount DECIMAL(10,2))
RETURNS TABLE
AS
RETURN (
    SELECT OrderID, CustomerName, OrderAmount
    FROM dbo.Orders
    WHERE OrderAmount >= @MinAmount
);

✅ Usage Example:

SELECT * FROM dbo.fn_GetHighValueOrders(200.00);

🧹 Optional Cleanup

-- DROP FUNCTION dbo.fn_ApplyDiscount;
-- DROP FUNCTION dbo.fn_GetHighValueOrders;
-- DROP TABLE dbo.Orders;

🎬 Watch the Full Tutorial

Blog post written with the help of ChatGPT.