HAVING without GROUP BY is legal but almost always a mistake - the
author usually meant WHERE. The engine treats the whole result set as
one group, which can produce surprising row counts.

Should fail

SELECT total FROM orders HAVING total > 1000;

Should pass

SELECT region, SUM(total)
FROM orders
GROUP BY region
HAVING SUM(total) > 1000;

Implementation hints

• Multi-line rule (multiline = True, override check_statement).
• Detect HAVING without a preceding GROUP BY in the same statement.
• Model after W006 orderby-without-limit which uses the same pattern.
• Severity: warning.

Estimated LOC: ~30 code + ~20 test.