Answer
Cardinality estimation predicts how many rows a query will process.
Accurate estimates are critical for choosing efficient join types and memory usage.
Quick Answer
Cardinality estimation predicts how many rows each operation in a plan will produce. If the estimate is 10 rows but the real result is 100,000, SQL Server builds the wrong plan — wrong join type, wrong memory grant, wrong index choice. Accurate statistics are what keep cardinality estimates correct.
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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