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Keys, duplicates and repeated entities

Check exact duplicate rows, duplicate keys and repeated timestamps. Concepts: Primary keys; exact vs key duplicates Project A: No ID column → check exact duplicate rows (expect 0). Without an ID you cannot detect the same person applying twice: write that as a limitation. Project B: Duplicate timestamps around daylight-saving changes; weather duplicates per city-hour.

Builds on: B14 · Build: Data Cleaning Clinic (messy customer data)