"Scans, Seeks, and Lookups"

1. What is a primary characteristic of a table scan in SQL Server?

It uses a clustered index efficiently It is only performed on small tables It reads every page of a heap It retrieves only requested rows from the index

2. In what scenario is a clustered index scan considered appropriate?

When the query needs a small fraction of rows When the query needs nearly all the rows When no other indexes are available When the table has fewer than 100 rows

3. What happens during a key lookup when executing a query?

It does not read any data It fetches additional columns from the base row It replaces the need for indexed columns It optimizes the clustered index

4. Why might SQL Server perform a scan instead of a seek when executing a query?

When the index is not present When the rate of returned rows exceeds a certain threshold When the table is small enough When SQL Server is optimizing for speed

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