Level 0: Sky Zone: CREATE TABLE, JOIN, NULL, ...

Level 1: Surface Zone: ACID, outer joins, normal forms, ...

Level 2: Sunlight Zone: Connection pools, LATERAL Join, Stored Procedures, ...

Level 3: Twilight Zone: Isolation levels, ZigZag Join, Triggers, ...

Level 4: Midnight Zone: Denormalization, SELECT FOR UPDATE, star schemas, ...

Level 5: Abyssal Zone: MATCH PARTIAL foreign keys, 'null'::jsonb IS NULL = false, ...

Level 6: Hadal Zone: volcano model, join ordering is NP Hard, ...

Level 7: Pitch Black Zone: NULL, the halloween problem, fsyncgate, ...