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IN, BETWEEN, and Range Semantics / predict result
M07-A03 - Prediction - identify both inclusive BETWEEN endpoints
M07-A03 - Prediction - identify both inclusive BETWEEN endpoints. Express membership, inclusive ranges, and half-open alternatives deliberately.
- Result grain
- one BETWEEN endpoint prediction per product row
- Exact columns
- product_id; price; in_price_band
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Cursor at line 1, column 1.
Scenario
Express list membership and ranges precisely: refactor repeated equality with IN, treat BETWEEN endpoints as inclusive, and choose half-open timestamp bounds when the period demands it.
IN, BETWEEN, and Range Semantics / predict result
One-sentence task
M07-A03 - Prediction - identify both inclusive BETWEEN endpoints. Express membership, inclusive ranges, and half-open alternatives deliberately.
Learn mode disclosure
Theory, concept names, full schema help, and progressive hints are available.
Structured output contract
- Result grain
- one BETWEEN endpoint prediction per product row
- Exact columns
- product_id; price; in_price_band
- 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
- order by product_id
- Validation
- select-only; hidden deterministic variants.
Relevant tables
Time and difficulty
- Estimated time
- 6 minutes
- Difficulty
- 2/5
Objective and concepts
State the requested SQL output contract for in, between, and range semantics using source grain, columns, ordering, and edge-case evidence.
Glossary links
Concept material
SQL Trail treats every query as an evidence trail: identify source grain, transform rows deliberately, then compare output to a shared contract.
A passing query must handle hidden nulls, ties, boundaries, and no-match rows when the contract makes them relevant.
Syntax card
SELECT <requested_columns>
FROM <source_table>
WHERE <source_population_filter>
GROUP BY <result_grain_columns>
ORDER BY <deterministic_tie_breakers>;- <requested_columns> means the exact output columns, aliases, and order from the visible contract.
- <source_population_filter> means the row population definition, not a copied visible-row value.
- <deterministic_tie_breakers> means all ordering and tie rules needed for repeatable output.
Why this works
IN keeps the same repeated-equality semantics while making the accepted value list explicit.
Edge cases
Hidden variants preserve nulls, ties, duplicates, boundaries, no-match rows, and alternate row order when those risks apply.
PostgreSQL note
The local engine uses PostgreSQL-compatible syntax, including explicit NULL predicates, deterministic ORDER BY clauses, and transactional grading.
Worked example
SELECT order_id, status FROM orders WHERE status IN ('completed', 'returned') ORDER BY order_id;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.
PostgreSQL-compatible local checks
Queries run in a local PGlite worker with PostgreSQL-style syntax and transactional grading.
- IN lists contain values: The column name is repeated inside the IN list or mixed with literal values. Repair: Write the source column once before IN, then list only quoted text values or typed literals inside parentheses.
- BETWEEN includes both endpoints: Rows exactly on the lower or upper bound are excluded as if BETWEEN were exclusive. Repair: Treat BETWEEN a AND b as >= a and <= b for scalar values.
- NOT IN is not automatically null-safe: A missing candidate value is expected to behave like a normal value in anti-list logic. Repair: Keep NULL handling explicit; this module flags the warning before later anti-join and null lessons.
- Timestamp periods need the next boundary: A date-time period ends at a guessed 23:59:59 value and misses later precision. Repair: Use >= period_start and < next_period_start for half-open timestamp periods.
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