JSON

duckdb -c "SELECT * FROM read_json_auto('data.json')"


### Open persistent databases
```bash
# Create/open database
duckdb my_database.duckdb

# Read-only mode
duckdb -readonly existing.duckdb

Command Line Arguments

Output formats (as flags)

Flag	Format
`-csv`	Comma-separated
`-json`	JSON array
`-table`	ASCII table
`-markdown`	Markdown table
`-html`	HTML table
`-line`	One value per line

Execution arguments

Argument	Description
`-c COMMAND`	Run SQL and exit
`-f FILENAME`	Run script from file
`-init FILE`	Use alternative to ~/.duckdbrc
`-readonly`	Open in read-only mode
`-echo`	Show commands before execution
`-bail`	Stop on first error
`-header` / `-noheader`	Show/hide column headers
`-nullvalue TEXT`	Text for NULL values
`-separator SEP`	Column separator

Data Conversion

CSV to Parquet

duckdb -c "COPY (SELECT * FROM 'input.csv') TO 'output.parquet' (FORMAT PARQUET)"

Parquet to CSV

duckdb -c "COPY (SELECT * FROM 'input.parquet') TO 'output.csv' (HEADER, DELIMITER ',')"

JSON to Parquet

duckdb -c "COPY (SELECT * FROM read_json_auto('input.json')) TO 'output.parquet' (FORMAT PARQUET)"

Convert with filtering

duckdb -c "COPY (SELECT * FROM 'data.csv' WHERE amount > 1000) TO 'filtered.parquet' (FORMAT PARQUET)"

Dot Commands

Schema inspection

Command	Description
`.tables [pattern]`	Show tables (with LIKE pattern)
`.schema [table]`	Show CREATE statements
`.databases`	Show attached databases

Output control

Command	Description
`.mode FORMAT`	Change output format
`.output file`	Send output to file
`.once file`	Next output to file
`.headers on/off`	Show/hide column headers
`.separator COL ROW`	Set separators

Queries

Command	Description
`.timer on/off`	Show execution time
`.echo on/off`	Show commands before execution
`.bail on/off`	Stop on error
`.read file.sql`	Run SQL from file

Editing

Command	Description
`.edit` or `\e`	Open query in external editor
`.help [pattern]`	Show help

Output Formats (18 available)

Data export

csv - Comma-separated for spreadsheets
tabs - Tab-separated
json - JSON array
jsonlines - Newline-delimited JSON (streaming)

Readable formats

duckbox (default) - Pretty ASCII with unicode box-drawing
table - Simple ASCII table
markdown - For documentation
html - HTML table
latex - For academic papers

Specialized

insert TABLE - SQL INSERT statements
column - Columns with adjustable width
line - One value per line
list - Pipe-separated
trash - Discard output

Keyboard Shortcuts (macOS/Linux)

Navigation

Shortcut	Action
`Home` / `End`	Start/end of line
`Ctrl+Left/Right`	Jump word
`Ctrl+A` / `Ctrl+E`	Start/end of buffer

History

Shortcut	Action
`Ctrl+P` / `Ctrl+N`	Previous/next command
`Ctrl+R`	Search history
`Alt+<` / `Alt+>`	First/last in history

Editing

Shortcut	Action
`Ctrl+W`	Delete word backward
`Alt+D`	Delete word forward
`Alt+U` / `Alt+L`	Uppercase/lowercase word
`Ctrl+K`	Delete to end of line

Autocomplete

Shortcut	Action
`Tab`	Autocomplete / next suggestion
`Shift+Tab`	Previous suggestion
`Esc+Esc`	Undo autocomplete

Autocomplete

Context-aware autocomplete activated with Tab:

Keywords - SQL commands
Table names - Database objects
Column names - Fields and functions
File names - Path completion

Database Operations

Create table from file

CREATE TABLE sales AS SELECT * FROM 'sales_2024.csv';

Insert data

INSERT INTO sales SELECT * FROM 'sales_2025.csv';

Export table

COPY sales TO 'backup.parquet' (FORMAT PARQUET);

Analysis Examples

Quick statistics

SELECT
    COUNT(*) as count,
    AVG(amount) as average,
    SUM(amount) as total
FROM 'transactions.csv';

Grouping

SELECT
    category,
    COUNT(*) as count,
    SUM(amount) as total
FROM 'data.csv'
GROUP BY category
ORDER BY total DESC;

Join on files

SELECT a.*, b.name
FROM 'orders.csv' a
JOIN 'customers.parquet' b ON a.customer_id = b.id;

Describe data

DESCRIBE SELECT * FROM 'data.csv';

Pipe and stdin

# Read from stdin
cat data.csv | duckdb -c "SELECT * FROM read_csv('/dev/stdin')"

# Pipe to another command
duckdb -csv -c "SELECT * FROM 'data.parquet'" | head -20

# Write to stdout
duckdb -c "COPY (SELECT * FROM 'data.csv') TO '/dev/stdout' (FORMAT CSV)"

Configuration

Save common settings in ~/.duckdbrc:

.timer on
.mode duckbox
.maxrows 50
.highlight on

Syntax highlighting colors

.keyword green
.constant yellow
.comment brightblack
.error red

External Editor

Open complex queries in your editor:

.edit

Editor is chosen from: DUCKDB_EDITOR → EDITOR → VISUAL → vi

Safe Mode

Secure mode that restricts file access. When enabled:

No external file access
Disables .read, .output, .import, .sh etc.
Cannot be disabled in the same session

Tips

Use LIMIT on large files for quick preview
Parquet is faster than CSV for repeated queries
read_csv_auto and read_json_auto guess column types
Arguments are processed in order (like SQLite CLI)
WSL2 may show incorrect memory_limit values on some Ubuntu versions

duckdb-en

DuckDB CLI Specialist

Quick Start

Read data files directly with SQL