/motherduck-duckdb-sql

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.
license: MIT

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.
• 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.

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.
• 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.

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

• Read `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