Mode disclosure
All modes use one coherent workspace; only disclosure and guidance change. Review mode hides concept labels until submission, keeps a due counter visible, and lets you Skip for Later without losing work.
Keys, Relationships, Cardinality, and Join Planning / predict result
RD-A01 - Plan a join path and intermediate grains in an unfamiliar schema
RD-A01 - Plan a join path and intermediate grains in an unfamiliar schema. Plan a join path and predict row multiplication before writing JOIN syntax.
- Result grain
- one row per category including null category
- Exact columns
- category; revenue
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Cursor at line 1, column 1.
Scenario
Retrieve the skill without relying on the lesson label.
Review mode / concept labels hidden until submission
One-sentence task
RD-A01 - Plan a join path and intermediate grains in an unfamiliar schema. Plan a join path and predict row multiplication before writing JOIN syntax.
Review mode disclosure
Concept labels hidden until submission. Use the due counter and Skip for Later without losing the draft.
Structured output contract
- Result grain
- one row per category including null category
- Exact columns
- category; revenue
- Source population
- Use the prompt setup plus FROM, JOIN, WHERE, and subquery predicates as the source population. Visible rows are only examples.
- Grouping
- Group only at the requested output grain: one row per category including null category.
- Ordering
- order by revenue descending then category
- Validation
- select-only; hidden deterministic variants.
Relevant tables
Time and difficulty
- Estimated time
- 5 minutes
- Difficulty
- 4/5
Objective and concepts
Concept labels are hidden until submission so retrieval stays honest.
Assumptions, dialect notes, and common traps
- Duplicate policy
- Preserve duplicate facts unless the prompt explicitly asks for distinct tuples or set semantics.
- Null policy
- Preserve NULL, empty string, zero, and false as distinct values unless the contract says to display a fallback.
- Tie-breakers
- Use every ordering rule in the contract and end tied business metrics with deterministic secondary keys when needed.
- Zero-related entities
- Do not invent zero rows unless the contract asks for preserved parents, missing entities, or complete periods.
- Numeric tolerance
- Round only at the requested final stage; hidden checks use the contract precision rather than visible formatting luck.
Opened hints
Hints are disabled during active review or challenge assessment and become available after submission or outside assessment mode.