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What does SARGable mean, and why does it matter?

SQL Server Query Tuning Advanced 3–5 Yrs5+ Yrs Conceptual 1 min read

Quick Answer

SARGable (“Search ARGument able”) means a predicate can use an index seek. Wrapping the column in a function (YEAR(OrderDate) = 2026), applying arithmetic to it, using a leading % in LIKE, or forcing an implicit type conversion all make a predicate non-SARGable, so the engine must scan.

SARGable means the predicate is written in a way that lets SQL Server seek an index. The moment you put a function around the column — YEAR(OrderDate) = 2026, UPPER(name) = ..., arithmetic on the column, or a LIKE with a leading wildcard — it can't seek any more and has to scan and evaluate every row. So I rewrite those: the year example becomes a date range, >= Jan 1 and < Jan 1 next year. The sneaky one is implicit conversion — an nvarchar column compared to a varchar parameter converts the whole column.

  • Non-SARGable → SARGable rewrites:
    • YEAR(d) = 2026 → d >= '2026-01-01' AND d < '2027-01-01'
    • ISNULL(status,0) = 0 → status = 0 OR status IS NULL
    • col * 2 > 100 → col > 50
    • LIKE '%abc' → can't seek; consider a computed reversed column or full-text
  • Implicit conversion: comparing an NVARCHAR column to a VARCHAR parameter (or vice versa) can convert the whole column and kill the seek — match the parameter type.
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