Read an execution plan

This lesson uses DDI_SQL_Training dataset v1.0.0 on SQL Server 2019 or later. Use a real query to identify access, join, and row-estimate decisions in its plan.

Run the example

SELECT TOP (3) o.OrderID, c.FirstName
FROM dbo.Orders AS o
JOIN dbo.Customers AS c ON c.CustomerID = o.CustomerID
WHERE o.OrderID BETWEEN 1 AND 100
ORDER BY o.OrderID;

Read it step by step

1. Run the query with Actual Execution Plan enabled in a SQL Server editor.
2. Read operators from data access through join and any sort or TOP; compare estimated and actual rows at each operator.
3. This page shows the verified result rows, not an invented fixed plan: the plan can differ by version, statistics, and settings.

Check the result

On the unmodified dataset, these are the first three matching orders by OrderID.

Practice

Run a similar query for OrderID 101–200 and inspect its actual plan.

SELECT TOP (3) o.OrderID, c.FirstName
FROM dbo.Orders AS o
JOIN dbo.Customers AS c ON c.CustomerID = o.CustomerID
WHERE o.OrderID BETWEEN 101 AND 200
ORDER BY o.OrderID;