Data & Settings Inspection

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DuckDB provides two ways to inspect your data: SQL Metadata Functions (which work in any environment like Go or Python) and CLI Dot Commands (exclusive to the terminal).

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Inspecting Tables and Views

To see what you are working with, use these commands:

Action	CLI Dot Command	SQL Equivalent
List all tables	.tables	SHOW TABLES;
Show table structure	.schema [table_name]	DESCRIBE [table_name];
Show columns/types	N/A	PRAGMA table_info('table_name');
List all views	.tables (included)	SELECT * FROM duckdb_views();

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Pro-Tip: Inspecting "External" Files

One of DuckDB's best features is inspecting a file before you even create a table.

-- See the schema of a Parquet file on your disk
DESCRIBE SELECT * FROM 'data/raw/yellow_taxi.parquet';

-- Peek at the first 5 rows
SELECT * FROM 'data/raw/yellow_taxi.parquet' LIMIT 5;

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Deep Schema Inspection

If you need to know more than just column names (like nullability, defaults, or internal storage info), use the Metadata Functions.

• SUMMARIZE: This is a DuckDB superpower. It gives you a statistical overview of every column (min, max, average, percentage of nulls, unique count).

  SUMMARIZE silver_taxi;

• duckdb_columns: Useful if you want to find every table that contains a specific column name (like user_id).

  SELECT table_name, column_name 
  FROM duckdb_columns() 
  WHERE column_name = 'vendor_id';

• .header on: Ensures column names are always visible (usually on by default).

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Navigating the File System

You don't have to leave DuckDB to see your files:

• .shell [command]: Run any terminal command from inside DuckDB.

  D .shell ls -lh ./data/raw

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Resource & Setting Inspection

Inspect DuckDB environment

As a Data Engineer, you need to know how much memory and CPU DuckDB is using.

• SET: Running SET; (with no arguments) shows every configuration option and its current value.

• PRAGMA platform: Tells you exactly which architecture and version you are running (useful for extension compatibility).

• PRAGMA memory_info: Shows current RAM usage and the "spill-to-disk" threshold.

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