SARG (Search ARGument Able) is the biggest reason queries go from 20ms → 10 seconds.
❌ Non-SARGable
WHERE YEAR(OrderDate) = 2024
This forces a full scan.
✔ SARGable Version
WHERE OrderDate >= '2024-01-01' AND OrderDate < '2025-01-01'
💡 Why It Matters
-
Enables index seeks
-
Saves CPU
-
Reduces IO dramatically