The mysql extension allows DuckDB to directly read and write data from/to a running MySQL instance. The data can be queried directly from the underlying MySQL database. Data can be loaded from MySQL tables into DuckDB tables, or vice versa.

Installing and Loading

To install the mysql extension, run:

INSTALL mysql;

The extension is loaded automatically upon first use. If you prefer to load it manually, run:

LOAD mysql;

Reading Data from MySQL

To make a MySQL database accessible to DuckDB use the ATTACH command with the mysql or the mysql_scanner type:

ATTACH 'host=localhost user=root port=0 database=mysql' AS mysqldb (TYPE mysql);
USE mysqldb;

Configuration

The connection string determines the parameters for how to connect to MySQL as a set of key=value pairs. Any options not provided are replaced by their default values, as per the table below. Connection information can also be specified with environment variables. If no option is provided explicitly, the MySQL extension tries to read it from an environment variable.

Configuring via Secrets

MySQL connection information can also be specified with secrets. The following syntax can be used to create a secret.

CREATE SECRET (
    TYPE mysql,
    HOST '127.0.0.1',
    PORT 0,
    DATABASE mysql,
    USER 'mysql',
    PASSWORD ''
);

The information from the secret will be used when ATTACH is called. We can leave the connection string empty to use all of the information stored in the secret.

ATTACH '' AS mysql_db (TYPE mysql);

We can use the connection string to override individual options. For example, to connect to a different database while still using the same credentials, we can override only the database name in the following manner.

ATTACH 'database=my_other_db' AS mysql_db (TYPE mysql);

By default, created secrets are temporary. Secrets can be persisted using the CREATE PERSISTENT SECRET command. Persistent secrets can be used across sessions.

Managing Multiple Secrets

Named secrets can be used to manage connections to multiple MySQL database instances. Secrets can be given a name upon creation.

CREATE SECRET mysql_secret_one (
    TYPE mysql,
    HOST '127.0.0.1',
    PORT 0,
    DATABASE mysql,
    USER 'mysql',
    PASSWORD ''
);

The secret can then be explicitly referenced using the SECRET parameter in the ATTACH.

ATTACH '' AS mysql_db_one (TYPE mysql, SECRET mysql_secret_one);

SSL Connections

The ssl connection parameters can be used to make SSL connections. Below is a description of the supported parameters.

Reading MySQL Tables

The tables in the MySQL database can be read as if they were normal DuckDB tables, but the underlying data is read directly from MySQL at query time.

SHOW ALL TABLES;

SELECT * FROM signed_integers;

It might be desirable to create a copy of the MySQL databases in DuckDB to prevent the system from re-reading the tables from MySQL continuously, particularly for large tables.

Data can be copied over from MySQL to DuckDB using standard SQL, for example:

CREATE TABLE duckdb_table AS FROM mysqlscanner.mysql_table;

Writing Data to MySQL

In addition to reading data from MySQL, create tables, ingest data into MySQL and make other modifications to a MySQL database using standard SQL queries.

This allows you to use DuckDB to, for example, export data that is stored in a MySQL database to Parquet, or read data from a Parquet file into MySQL.

Below is a brief example of how to create a new table in MySQL and load data into it.

ATTACH 'host=localhost user=root port=0 database=mysqlscanner' AS mysql_db (TYPE mysql);
CREATE TABLE mysql_db.tbl (id INTEGER, name VARCHAR);
INSERT INTO mysql_db.tbl VALUES (42, 'DuckDB');

Many operations on MySQL tables are supported. All these operations directly modify the MySQL database, and the result of subsequent operations can then be read using MySQL. Note that if modifications are not desired, ATTACH can be run with the READ_ONLY property which prevents making modifications to the underlying database. For example:

ATTACH 'host=localhost user=root port=0 database=mysqlscanner' AS mysql_db (TYPE mysql, READ_ONLY);

Supported Operations

Below is a list of supported operations.

CREATE TABLE

CREATE TABLE mysql_db.tbl (id INTEGER, name VARCHAR);

INSERT INTO

INSERT INTO mysql_db.tbl VALUES (42, 'DuckDB');

SELECT

SELECT * FROM mysql_db.tbl;

COPY

COPY mysql_db.tbl TO 'data.parquet';
COPY mysql_db.tbl FROM 'data.parquet';

You may also create a full copy of the database using the COPY FROM DATABASE statement:

COPY FROM DATABASE mysql_db TO my_duckdb_db;

UPDATE

UPDATE mysql_db.tbl
SET name = 'Woohoo'
WHERE id = 42;

DELETE

DELETE FROM mysql_db.tbl
WHERE id = 42;

ALTER TABLE

ALTER TABLE mysql_db.tbl
ADD COLUMN k INTEGER;

DROP TABLE

DROP TABLE mysql_db.tbl;

CREATE VIEW

CREATE VIEW mysql_db.v1 AS SELECT 42;

CREATE SCHEMA and DROP SCHEMA

CREATE SCHEMA mysql_db.s1;
CREATE TABLE mysql_db.s1.integers (i INTEGER);
INSERT INTO mysql_db.s1.integers VALUES (42);
SELECT * FROM mysql_db.s1.integers;

DROP SCHEMA mysql_db.s1;

Transactions

CREATE TABLE mysql_db.tmp (i INTEGER);
BEGIN;
INSERT INTO mysql_db.tmp VALUES (42);
SELECT * FROM mysql_db.tmp;

This returns:

ROLLBACK;
SELECT * FROM mysql_db.tmp;

This returns an empty table.

The DDL statements are not transactional in MySQL.

Running SQL Queries in MySQL

The mysql_query Table Function

The mysql_query table function allows you to run arbitrary read queries within an attached database. mysql_query takes the name of the attached MySQL database to execute the query in, as well as the SQL query to execute. The result of the query is returned. Single-quote strings are escaped by repeating the single quote twice.

mysql_query(attached_database::VARCHAR, query::VARCHAR)

For example:

ATTACH 'host=localhost database=mysql' AS mysqldb (TYPE mysql);
SELECT * FROM mysql_query('mysqldb', 'SELECT * FROM cars LIMIT 3');

The mysql_execute Function

The mysql_execute function allows running arbitrary queries within MySQL, including statements that update the schema and content of the database.

ATTACH 'host=localhost database=mysql' AS mysqldb (TYPE mysql);
CALL mysql_execute('mysqldb', 'CREATE TABLE my_table (i INTEGER)');

Settings

Schema Cache

To avoid having to continuously fetch schema data from MySQL, DuckDB keeps schema information – such as the names of tables, their columns, etc. – cached. If changes are made to the schema through a different connection to the MySQL instance, such as new columns being added to a table, the cached schema information might be outdated. In this case, the function mysql_clear_cache can be executed to clear the internal caches.

CALL mysql_clear_cache();