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These are frequent mid degree questions that you’re anticipated to know within the interview course of:
FAANG interviews love testing your capacity to mannequin relationships throughout the similar entity — assume org charts, threaded feedback, or recurring person conduct. A self-join is your secret weapon for turning nested or sequential information into flat, queryable constructions.
✅ Core Method:
Be a part of the identical desk utilizing aliases (e.g., staff e1, staff e2) to match relationships between rows.
Basic use case:
“Discover staff who earn greater than their managers”
Self-join one1.manager_id = e2.employee_id, then evaluate salaries.
🧠 What to Watch For:
- Keep away from Cartesian merchandise with correct
ONclauses. - Index international key relationships to keep away from efficiency hits.
💡 Attempt This Actual Interview Immediate:
Discover all customers who…
