Quick Answer
SARGable expressions allow the optimizer to use index seeks by passing the filter condition directly into the index. Non-SARGable expressions (wrapping the column in a function, CAST, or CONVERT) force a table or index scan. Always filter on the raw column, and ensure data types match without implicit conversion.
Answer
A SARGable expression allows SQL Server to use indexes efficiently. Non-SARGable predicates (functions on columns, mismatched types) force scans, increasing logical reads and slowing queries. SARGability is foundational for scaling queries on large datasets.
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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.
