SQL patterns I use to catch transaction fraud

The article outlines six SQL-based patterns for detecting transaction fraud, starting with the simplest approaches like velocity (unusually high transaction frequency) and impossible travel (transactions occurring in distant locations too quickly to be legitimate). The author emphasizes that effective fraud detection relies on SQL queries against transaction tables rather than complex machine learning, and recommends tuning thresholds and building detections in order of simplicity while maintaining whitelists for legitimate high-volume users.