Find Repeat Values in SQL: THE WAR ROOM

THE WAR ROOM is chapter 12 and a duplicate-detection drill in disguise. The INCIDENTS table logs every security breach with an AGENT_ID; FIELD_AGENTS holds the roster. You join them, count incidents per agent with GROUP BY, and flag the agents whose count crosses a threshold with HAVING.

Finding values that appear more than N times is one of the most common SQL interview questions there is, usually phrased as finding duplicate records. Here it plays out as a counterintelligence review: one query, and the liabilities have nowhere to hide.

Three stages take you from the raw incident log to the final repeat-offender list.

This is the shape of query you practice here, not the answer to any mission. The real stages come with their own data, objectives, and hints.

SELECT FIELD_AGENTS.CODENAME, COUNT(*) AS INCIDENT_TOTAL
FROM FIELD_AGENTS
INNER JOIN INCIDENTS ON FIELD_AGENTS.ID = INCIDENTS.AGENT_ID
GROUP BY FIELD_AGENTS.CODENAME
HAVING COUNT(*) >= 4;

Free guides that pair well with this chapter:

• Window Functions: ROW_NUMBER, RANK, LEAD, LAG
• GROUP BY and HAVING: The Difference Explained