Spatial SQL

Solve the query in the engine the user has chosen. Read references/spatial-sql.md for the relevant engine and query patterns, and references/formats-and-crs.md when coordinate or format semantics matter.

When the user has dlt, Dagster, dbt, QGIS or Observable in their stack, read references/established-stack.md for ownership and integration boundaries. Preserve their chosen tools; retain source pins, GIS correctness and reproducible evidence. Do not duplicate their SQL, ingestion or scheduler definitions.

Query workflow

1. Establish the engine/version, available spatial functions, geometry versus geography types, CRS/SRID, input grain, expected result and scale. Inspect the existing query and plan when available. Do not assume different engines share function signatures, boundary semantics or index behavior.
2. Express the intended spatial relationship precisely. Resolve intersects versus contains/covers, boundary inclusion, null/empty/invalid geometries, and whether several spatial matches should duplicate an entity or produce a single membership result.
3. Make distance, area and buffers use the intended units and method. A geographic geometry in EPSG:4326 does not acquire metre units from a numeric threshold. Use the engine's explicitly supported geodesic/geography operation, or a projected CRS whose area of use contains the data's known extent. For distance and within-distance tests on an unknown or wide extent, prefer an operation the engine documents as geodesic for the geometry types involved; do not guess a UTM zone or national grid. A geography type does not make every operation geodesic: check buffers and other constructions per operation. Assigning an SRID is not coordinate transformation; Web Mercator is not a general metric-analysis CRS.
4. Preserve analytical correctness while improving execution. Consider spatial indexes or candidate filters, predicate pushdown, partition pruning and join cardinality. An expression or cast can prevent use of an existing index; verify the relevant plan instead of promising index use by syntax.
5. Run a small meaningful control when an engine is available: qualifying and non-qualifying features, a boundary, and duplicate matches where relevant. Report actual execution evidence separately from a reasoned SQL review. An unavailable engine is not_testable, not a successful query run.

Return corrected SQL, consequential assumptions and a short explanation of correctness and performance. Do not create a full GIS project for a bounded query review. Preserve source data; an optimization must not silently change the metric, feature population or authoritative geometry.

When the task expands

Engine selection, shared-system design and joint compute/storage/delivery trade-offs belong with an installed open-map-stack or an explicit architecture discussion. Compiling a material analysis belongs with the generalist or reproducible-gis-project. Keep the SQL contribution bounded and supply the assumptions/evidence needed for that handoff; do not claim to have completed the whole analysis.

No project template, worked example or OpenMapStack CLI is needed for a bounded query task. Hand off the SQL and its assumptions to an installed open-map-stack or reproducible-gis-project if the user also wants a full project. Sibling skills are optional and are never automatically installed.

For optional product expertise, read references/companion-skills.md. Keep GIS correctness and the task boundaries above when using a companion.