The SQLite extension allows DuckDB to directly read and write data from a SQLite database file. The data can be queried directly from the underlying SQLite tables. Data can be loaded from SQLite tables into DuckDB tables, or vice versa.
To make a SQLite file accessible to DuckDB, use the ATTACH
command, for example with the bundled sakila.db
file:
ATTACH 'data/db/sakila.db' AS sakila;
USE sakila;
The tables in the file can be read as if they were normal DuckDB tables, but the underlying data is read directly from the SQLite tables in the file at query time.
SHOW TABLES;
You can query the tables using SQL, e.g. using the example queries from sakila-examples.sql
SELECT cat.name category_name,
Sum(Ifnull(pay.amount, 0)) revenue
FROM category cat
LEFT JOIN film_category flm_cat
ON cat.category_id = flm_cat.category_id
LEFT JOIN film fil
ON flm_cat.film_id = fil.film_id
LEFT JOIN inventory inv
ON fil.film_id = inv.film_id
LEFT JOIN rental ren
ON inv.inventory_id = ren.inventory_id
LEFT JOIN payment pay
ON ren.rental_id = pay.rental_id
GROUP BY cat.name
ORDER BY revenue DESC
LIMIT 5;
SQLite databases can also be opened directly and can be used transparently instead of a DuckDB database file. In any client, when connecting, a path to a SQLite database file can be provided and the SQLite database will be opened instead.
For example, with the shell:
$ > duckdb data/db/sakila.db
v0.9.1 401c8061c6
D SHOW tables;
┌────────────────────────┐
│ name │
│ varchar │
├────────────────────────┤
│ actor │
│ address │
│ category │
│ city │
│ country │
│ customer │
│ customer_list │
│ film │
│ film_actor │
│ film_category │
│ film_list │
│ film_text │
│ inventory │
│ language │
│ payment │
│ rental │
│ sales_by_film_category │
│ sales_by_store │
│ staff │
│ staff_list │
│ store │
├────────────────────────┤
│ 21 rows │
└────────────────────────┘
In addition to reading data from SQLite, the extension also allows you to create new SQLite database files, create tables, ingest data into SQLite and make other modifications to SQLite database files using standard SQL queries.
This allows you to use DuckDB to, for example, export data that is stored in a SQLite database to Parquet, or read data from a Parquet file into SQLite.
Below is a brief example of how to create a new SQLite database and load data into it.
ATTACH 'new_sqlite_database.db' AS sqlite_db (TYPE SQLITE);
CREATE TABLE sqlite_db.tbl(id INTEGER, name VARCHAR);
INSERT INTO sqlite_db.tbl VALUES (42, 'DuckDB');
The resulting SQLite database can then be read into from SQLite.
$r > sqlite3 new_sqlite_database.db
SQLite version 3.39.5 2022-10-14 20:58:05
sqlite> SELECT * FROM tbl;
id name
-- ------
42 DuckDB
Many operations on SQLite tables are supported. All these operations directly modify the SQLite database, and the result of subsequent operations can then be read using SQLite.
Below is a list of supported operations.
CREATE TABLE sqlite_db.tbl(id INTEGER, name VARCHAR);
INSERT INTO sqlite_db.tbl VALUES (42, 'DuckDB');
SELECT * FROM sqlite_db.tbl;
┌───────┬─────────┐
│ id │ name │
│ int64 │ varchar │
├───────┼─────────┤
│ 42 │ DuckDB │
└───────┴─────────┘
COPY sqlite_db.tbl TO 'data.parquet';
COPY sqlite_db.tbl FROM 'data.parquet';
UPDATE sqlite_db.tbl SET name='Woohoo' WHERE id=42;
DELETE FROM sqlite_db.tbl WHERE id=42;
ALTER TABLE sqlite_db.tbl ADD COLUMN k INTEGER;
DROP TABLE sqlite_db.tbl;
CREATE VIEW sqlite_db.v1 AS SELECT 42;
CREATE TABLE sqlite_db.tmp(i INTEGER);
BEGIN;
INSERT INTO sqlite_db.tmp VALUES (42);
SELECT * FROM sqlite_db.tmp;
┌───────┐
│ i │
│ int64 │
├───────┤
│ 42 │
└───────┘
ROLLBACK;
SELECT * FROM sqlite_db.tmp;
┌────────┐
│ i │
│ int64 │
├────────┤
│ 0 rows │
└────────┘
To build, type
make
To run, run the bundled duckdb
shell:
./build/release/duckdb -unsigned
Then, load the SQLite extension like so:
LOAD 'build/release/extension/sqlite_scanner/sqlite_scanner.duckdb_extension';