Answer
A composite index includes multiple columns, used when queries filter or sort using those column combinations.
The order of columns is important because SQL Server can only efficiently use leading key columns.
Quick Answer
A composite index covers multiple columns. Useful when your WHERE clause filters on a combination of columns together. The column order matters — the index is most effective when the leading column appears in the filter. A (LastName, FirstName) index won't help a query filtering only on FirstName.
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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