Answer
Large IN lists complicate cardinality estimation and increase parsing overhead. SQL Server may misestimate row counts, leading to inefficient join choices. Using temp tables or joins improves accuracy and performance.
Quick Answer
Large IN lists force SQL Server to evaluate many OR conditions or build a large hash structure. For very long lists (1000+ values), performance degrades because the optimizer can't estimate the combined selectivity well. Alternative: load the values into a temp table and JOIN — SQL Server handles joins far more efficiently than giant IN lists.
S
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