Flag rows in SQL (DuckDB)

When to use it

Unusual but possibly legitimate values that need human review.

How

A boolean expression in the SELECT list.

CAST(amount AS DECIMAL(12,2)) > 5000.00 AS needs_review

• Use COALESCE(..., false) if missing values must be false rather than NULL.

Pitfalls

• Deleting or capping instead of flagging.
• Getting the boundary wrong (> versus >=).