DuckDB SQL Reference for MotherDuck

Use this skill when you need exact DuckDB syntax, function behavior, or a quick sanity check that a statement will actually work on MotherDuck.

Source Of Truth

• Prefer current DuckDB SQL docs for language features and function semantics.
• Use current MotherDuck SQL docs for MotherDuck-only commands such as shares, secrets, snapshots, and Dive operations.
• Check MotherDuck version-lifecycle docs for newly released DuckDB features before promising they are available in MotherDuck.
• Treat upstream DuckDB 1.5.x docs as ahead of MotherDuck unless the current MotherDuck lifecycle docs confirm the same DuckDB version and feature surface.
• Distinguish upstream DuckDB current-version docs from MotherDuck-supported DuckDB versions; MotherDuck can lag upstream current for client compatibility and SQL feature support.
• If the connection path matters, verify behavior against the current Postgres-endpoint docs before promising server-mode support.

Default Posture

• Write DuckDB SQL, not PostgreSQL SQL, even when the client connects through the Postgres endpoint.
• Use fully qualified "database"."schema"."table" names once more than one database or share is in scope.
• Prefer DuckDB-native constructs when they simplify the query: GROUP BY ALL, QUALIFY, UNION BY NAME, arg_max, EXCLUDE, and REPLACE.
• When porting SQL from another engine, translate functions, date arithmetic, identifier quoting, and type casts explicitly instead of assuming compatibility.
• For upstream DuckDB 1.5 features such as VARIANT, native GEOMETRY, date_trunc return-type changes, ODBC scanner behavior, or lakehouse-format changes, verify current MotherDuck support before adding them to production guidance.
• Check whether the statement depends on local files, extension install/load, temporary-table behavior, or other client-only features before claiming it will work in MotherDuck.
• Treat snapshot, restore, and UNDROP DATABASE statements as operational SQL with plan-specific retention behavior, not ordinary analytical syntax.
• Treat MotherDuck SQL as an additional surface on top of DuckDB SQL, not a replacement for it.

Workflow

1. Confirm the connection path and whether the question is about syntax, feature support, or a specific error.
2. Write or repair the statement in DuckDB SQL first.
3. Verify any MotherDuck-only command or server-mode limitation against the current docs.
4. If the user needs exact syntax or function details, open references/SYNTAX_REFERENCE.md.

Open Next

• references/SYNTAX_REFERENCE.md for DuckDB data types, friendly SQL features, functions, complex types, and common MotherDuck-specific gotchas

Related Skills

• motherduck-query for writing and validating analytical SQL against live MotherDuck data
• motherduck-connect when syntax support depends on PG endpoint versus native DuckDB behavior
• motherduck-explore when the problem is really missing schema context rather than missing syntax knowledge