Answer
A composite index includes multiple columns and is used left to right, making column order important for optimization.
Quick Answer
Composite index covers multiple columns: CREATE INDEX ON orders (user_id, created_at). Useful when queries filter on multiple columns together. Index prefix rule: a composite index on (a, b, c) can be used for queries on (a), (a, b), or (a, b, c) but NOT (b) alone. Put the most selective and most frequently filtered column first.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ