beginner~4h
Indexes — Clustered, Non-Clustered, Composite, Covering
Indexes are database structures that improve query performance by allowing fast data lookup without full table scans. Understanding indexes is one of the most critical skills for database performance
Learning objectives
- Explain why an index speeds up reads but slows down writes, in terms of the underlying data structure.
- Distinguish a clustered index from a non-clustered one, and explain why a table can have only one of the former.
- Apply the leftmost-prefix rule to predict whether a composite index will actually be used by a given query.
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Indexes — Clustered, Non-Clustered, Composite, Covering