duckdb cheatsheet

Duckdb cheatsheet.md

Duckdb cheatsheet

Use the following to work with duckdb

DESCRIBE command can be used for introspection

-- Create or replace the books table
CREATE OR REPLACE TABLE books (
  id BIGINT PRIMARY KEY,
  title VARCHAR NOT NULL DEFAULT 'Untitled',
  genres_array VARCHAR[] default [],
  publication_date DATE DEFAULT CURRENT_DATE,
  price DECIMAL(10, 2)
);

describe books

column_name	column_type	null	key	default	extra
id	BIGINT	NO	PRI
title	VARCHAR	NO		'Untitled'
genres_array	VARCHAR[]	YES		main.list_value()
publication_date	DATE	YES		CURRENT_DATE
price	DECIMAL(10,2)	YES

create json using struct_pack() and json cast or to_json()

SELECT 
  struct_pack(n:=1, str:='something') as my_struct,
  to_json(struct_pack(n:=1, str:='something')) as to_json_ed,
  struct_pack(n:=1, str:='something')::json as casted_json

my_struct	to_json_ed	casted_json
{"n": 1, "str": "something"}	{"n":1,"str":"something"}	{"n":1,"str":"something"}

if you need to do something special cast to json from string

Eg, duckdb syntax does not support empty structs, can use cast string for that

select '{}'::json

CAST('{}' AS "json")
{}

Duckdb has native arrays

use native [] syntax for arrays

select [] as empty, [{'a':1}] as such_nice_array_of_struct, [{'a':1}]::json as wow_json, array_value({'a':1}) array_value_is_verbose, array_agg(1)

empty	such_nice_array_of_struct	wow_json	array_value_is_verbose	array_agg_is_verbose
[]	[{"a": 1}]	[{"a":1}]	[{"a": 1}]	[1]

Unix time conversions

use epoch_ms, epoch_ns, epoch_us

select current_timestamp, epoch_us(CURRENT_TIMESTAMP)

epoch_ms(CURRENT_TIMESTAMP)
1738238834061