Chapter 21A: Reading the SQL Your Agent Wrote Quiz

Twenty questions. No tricks. If you have walked through the eight lessons and the capstone, you will know these answers. Each question maps to one of the silent failure modes or one of the reading habits the chapter taught.

Scoring guidance:

• 18-20: ready to review agent-produced SQL in production
• 15-17: solid foundation, revisit the lessons where you missed
• 11-14: redo the capstone before relying on this skill at work
• <=10: rerun the chapter starting at Lesson 1, slowly

Best practice: answer once without notes, then review misses and retake after targeted repair.

What This Quiz Measures

• the five reading questions
• the four silent SQL failures
• INNER vs LEFT JOIN behaviour
• HAVING vs WHERE
• NULL behaviour in filters and aggregates
• safe write practice (BEGIN/ROLLBACK, missing WHERE detection)
• schema reading and constraint recognition
• JSONB and pgvector recognition
• EXPLAIN plan reading at the Seq Scan vs Index Scan level

Question-to-Outcome Map

Outcome IDs:

• O1 Reading posture and silent failure recognition
• O2 SELECT/WHERE/ORDER BY/LIMIT reading
• O3 JOIN reading (INNER vs LEFT, missing rows)
• O4 GROUP BY / HAVING / aggregate traps
• O5 Write reading and transaction safety
• O6 Schema and constraint reading
• O7 JSONB, pgvector, EXPLAIN recognition

Question	Primary outcome
Q1	O1
Q2	O1
Q3	O2
Q4	O2
Q5	O2
Q6	O3
Q7	O3
Q8	O3
Q9	O4
Q10	O4
Q11	O4
Q12	O5
Q13	O5
Q14	O5
Q15	O6
Q16	O6
Q17	O6
Q18	O7
Q19	O7
Q20	O7

Checking access...