SQL
When to use
Use this skill for sql when you need to write a correct and explainable query for the target schema. The expected result is a query with assumptions and expected result.
Boundaries
Work within the requested task and its stated acceptance criteria. Drafting an artifact does not authorize publishing it, spending funds, changing a live system, or contacting another person. Identify any such action separately before taking it.
Inputs
Inspect schemas, data lineage, row grain, volumes, freshness, and downstream consumers. Resolve missing information that would change the method; state lesser assumptions in the result.
Method
- Diagnose. Map tables or collections, keys, row grain, indexes, volumes, consumers, and expected freshness.
- Decide. Choose a transformation or storage design that preserves contracts and can be replayed.
- Produce. Build a query with assumptions and expected result from the inspected material; keep assumptions distinguishable from observed facts.
Decision rules
- Specify nulls, duplicates, late data, schema drift, and replay behavior before transformation or migration.
- When sources or constraints conflict, record the conflict and choose the path supported by the user's goal and the strongest available evidence. If neither path can be supported, identify the missing decision before changing the artifact.
Domain rules
- Define null, duplicate, late-arrival, and deletion behavior.
- Document migration, backfill, and rollback expectations.
Verification
Inspect joins, nulls, and query plan. Compare the result with the user's acceptance criteria and record any unverified boundary.
Reconcile sample and aggregate results; include query plan or pipeline metrics and rollback or backfill steps.
Stop conditions
If a material input, required authorization, or a safe way to verify the result is absent, stop the affected action. Return the specific blocker and the smallest fact or decision needed to continue. Do not report an unrun check as passed.
Output
Provide a query with assumptions and expected result. Include the decisive evidence and actual verification result. Name any artifact location and unresolved issue that affects its use.
