motherduck-duckdb-sql - SKILL.md Agent Skill

name: motherduck-duckdb-sql description: DuckDB SQL reference for MotherDuck. Use when you need exact DuckDB syntax or function behavior, friendly SQL features like QUALIFY, GROUP BY ALL, or list/struct types, MotherDuck-specific SQL such as shares, secrets, snapshots, or UNDROP, or to fix SQL errors and PostgreSQL-style SQL that fails on MotherDuck. argument-hint: [syntax-or-error] license: MIT

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

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.
MotherDuck can lag upstream DuckDB releases for client compatibility; check MotherDuck version-lifecycle docs before promising newly released DuckDB syntax or types are available.
If the connection path matters, verify behavior against the current Postgres-endpoint docs before promising server-mode support.

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.
Verify current MotherDuck support before relying on recently released upstream DuckDB features such as VARIANT, native GEOMETRY, MERGE INTO, or date_trunc return-type changes.
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.

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

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

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