Mode disclosure
All modes use one coherent workspace; only disclosure and guidance change. Practice mode uses a concise prompt, normal schema, optional hints, and the same local Run and Check pipeline.
INNER JOIN and Qualified Columns / guided completion
M17-A01 - Fill gap - complete a key-to-foreign-key ON condition
M17-A01 - Fill gap - complete a key-to-foreign-key ON condition. Combine matching rows on verified keys with readable aliases and qualified references.
- Result grain
- one matched order row with customer context
- Exact columns
- order_id; customer_name
SQL editor shortcuts: Ctrl or Command Enter runs the query, Ctrl or Command Shift Enter checks it, Alt H opens the next hint, Ctrl or Command slash toggles a line comment, Ctrl or Command Shift F formats the SQL, and Escape closes transient UI.
Cursor at line 1, column 1.
Scenario
Write inner joins on verified keys: complete ON conditions, predict one-to-many output, qualify ambiguous columns, repair wrong ID joins, and preserve line-item grain.
INNER JOIN and Qualified Columns / guided completion
One-sentence task
M17-A01 - Fill gap - complete a key-to-foreign-key ON condition. Combine matching rows on verified keys with readable aliases and qualified references.
Practice mode disclosure
Concise prompt, normal schema help, optional hints, and the same checker workspace are available.
Structured output contract
- Result grain
- one matched order row with customer context
- Exact columns
- order_id; customer_name
- Source population
- Use the prompt setup plus FROM, JOIN, WHERE, and subquery predicates as the source population. Visible rows are only examples.
- Grouping
- Do not collapse rows unless the contract explicitly asks for aggregation, distinct tuples, or set semantics.
- Ordering
- return order_id; join orders to customers on the customer_id foreign key; order by order_id
- Validation
- select-only; hidden deterministic variants.
Relevant tables
Time and difficulty
- Estimated time
- 5 minutes
- Difficulty
- 3/5
Objective and concepts
Practice mode keeps the prompt concise; open hints only if you choose guided help.
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
- Use exact semantic comparison unless the activity explicitly declares a numeric tolerance.
Opened hints
No hints opened yet.