Cover a query with INCLUDE columns on an index

A covering index satisfies a query entirely from the index without touching the base table. The INCLUDE clause adds non-key columns to the index leaf level.

-- Query you want to cover
SELECT OrderId, CustomerId, TotalAmount
FROM Orders
WHERE CustomerId = @id AND StatusId = 1;

-- Index that covers it
CREATE INDEX IX_Orders_Customer_Status
ON Orders (CustomerId, StatusId)
INCLUDE (TotalAmount);

CustomerId and StatusId are the key columns (used for seeking). TotalAmount is included so SQL Server can return it without a key lookup back to the clustered index.

Without INCLUDE, SQL Server does a key lookup for every row the index finds — visible as a “Key Lookup” operator in the execution plan, often the bottleneck on high-traffic queries.

Check your execution plan first. If you see Key Lookup with high estimated rows, INCLUDE the columns it’s fetching.